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postgresql/contrib/pg_stat_statements/pg_stat_statements.c

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/*-------------------------------------------------------------------------
*
* pg_stat_statements.c
* Track statement planning and execution times as well as resource
* usage across a whole database cluster.
*
* Execution costs are totaled for each distinct source query, and kept in
* a shared hashtable. (We track only as many distinct queries as will fit
* in the designated amount of shared memory.)
*
* Starting in Postgres 9.2, this module normalized query entries. As of
* Postgres 14, the normalization is done by the core if compute_query_id is
* enabled, or optionally by third-party modules.
*
* To facilitate presenting entries to users, we create "representative" query
* strings in which constants are replaced with parameter symbols ($n), to
* make it clearer what a normalized entry can represent. To save on shared
* memory, and to avoid having to truncate oversized query strings, we store
* these strings in a temporary external query-texts file. Offsets into this
* file are kept in shared memory.
*
* Note about locking issues: to create or delete an entry in the shared
* hashtable, one must hold pgss->lock exclusively. Modifying any field
* in an entry except the counters requires the same. To look up an entry,
* one must hold the lock shared. To read or update the counters within
* an entry, one must hold the lock shared or exclusive (so the entry doesn't
* disappear!) and also take the entry's mutex spinlock.
* The shared state variable pgss->extent (the next free spot in the external
* query-text file) should be accessed only while holding either the
* pgss->mutex spinlock, or exclusive lock on pgss->lock. We use the mutex to
* allow reserving file space while holding only shared lock on pgss->lock.
* Rewriting the entire external query-text file, eg for garbage collection,
* requires holding pgss->lock exclusively; this allows individual entries
* in the file to be read or written while holding only shared lock.
*
*
* Copyright (c) 2008-2022, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/pg_stat_statements/pg_stat_statements.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <math.h>
#include <sys/stat.h>
#include <unistd.h>
#include "access/parallel.h"
#include "catalog/pg_authid.h"
#include "common/hashfn.h"
#include "executor/instrument.h"
#include "funcapi.h"
#include "jit/jit.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "optimizer/planner.h"
#include "parser/analyze.h"
#include "parser/parsetree.h"
#include "parser/scanner.h"
#include "parser/scansup.h"
#include "pgstat.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/lwlock.h"
#include "storage/shmem.h"
#include "storage/spin.h"
#include "tcop/utility.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/queryjumble.h"
#include "utils/memutils.h"
#include "utils/timestamp.h"
PG_MODULE_MAGIC;
/* Location of permanent stats file (valid when database is shut down) */
#define PGSS_DUMP_FILE PGSTAT_STAT_PERMANENT_DIRECTORY "/pg_stat_statements.stat"
/*
* Location of external query text file.
*/
#define PGSS_TEXT_FILE PG_STAT_TMP_DIR "/pgss_query_texts.stat"
/* Magic number identifying the stats file format */
static const uint32 PGSS_FILE_HEADER = 0x20220408;
/* PostgreSQL major version number, changes in which invalidate all entries */
static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM / 100;
/* XXX: Should USAGE_EXEC reflect execution time and/or buffer usage? */
#define USAGE_EXEC(duration) (1.0)
#define USAGE_INIT (1.0) /* including initial planning */
#define ASSUMED_MEDIAN_INIT (10.0) /* initial assumed median usage */
#define ASSUMED_LENGTH_INIT 1024 /* initial assumed mean query length */
#define USAGE_DECREASE_FACTOR (0.99) /* decreased every entry_dealloc */
#define STICKY_DECREASE_FACTOR (0.50) /* factor for sticky entries */
#define USAGE_DEALLOC_PERCENT 5 /* free this % of entries at once */
#define IS_STICKY(c) ((c.calls[PGSS_PLAN] + c.calls[PGSS_EXEC]) == 0)
/*
* Utility statements that pgss_ProcessUtility and pgss_post_parse_analyze
* ignores.
*/
#define PGSS_HANDLED_UTILITY(n) (!IsA(n, ExecuteStmt) && \
!IsA(n, PrepareStmt) && \
!IsA(n, DeallocateStmt))
/*
* Extension version number, for supporting older extension versions' objects
*/
typedef enum pgssVersion
{
PGSS_V1_0 = 0,
PGSS_V1_1,
PGSS_V1_2,
PGSS_V1_3,
PGSS_V1_8,
PGSS_V1_9,
PGSS_V1_10
} pgssVersion;
typedef enum pgssStoreKind
{
PGSS_INVALID = -1,
/*
* PGSS_PLAN and PGSS_EXEC must be respectively 0 and 1 as they're used to
* reference the underlying values in the arrays in the Counters struct,
* and this order is required in pg_stat_statements_internal().
*/
PGSS_PLAN = 0,
PGSS_EXEC,
PGSS_NUMKIND /* Must be last value of this enum */
} pgssStoreKind;
/*
* Hashtable key that defines the identity of a hashtable entry. We separate
* queries by user and by database even if they are otherwise identical.
*
* If you add a new key to this struct, make sure to teach pgss_store() to
* zero the padding bytes. Otherwise, things will break, because pgss_hash is
* created using HASH_BLOBS, and thus tag_hash is used to hash this.
*/
typedef struct pgssHashKey
{
Oid userid; /* user OID */
Oid dbid; /* database OID */
uint64 queryid; /* query identifier */
bool toplevel; /* query executed at top level */
} pgssHashKey;
/*
* The actual stats counters kept within pgssEntry.
*/
typedef struct Counters
{
int64 calls[PGSS_NUMKIND]; /* # of times planned/executed */
double total_time[PGSS_NUMKIND]; /* total planning/execution time,
* in msec */
double min_time[PGSS_NUMKIND]; /* minimum planning/execution time in
* msec */
double max_time[PGSS_NUMKIND]; /* maximum planning/execution time in
* msec */
double mean_time[PGSS_NUMKIND]; /* mean planning/execution time in
* msec */
double sum_var_time[PGSS_NUMKIND]; /* sum of variances in
* planning/execution time in msec */
int64 rows; /* total # of retrieved or affected rows */
int64 shared_blks_hit; /* # of shared buffer hits */
int64 shared_blks_read; /* # of shared disk blocks read */
int64 shared_blks_dirtied; /* # of shared disk blocks dirtied */
int64 shared_blks_written; /* # of shared disk blocks written */
int64 local_blks_hit; /* # of local buffer hits */
int64 local_blks_read; /* # of local disk blocks read */
int64 local_blks_dirtied; /* # of local disk blocks dirtied */
int64 local_blks_written; /* # of local disk blocks written */
int64 temp_blks_read; /* # of temp blocks read */
int64 temp_blks_written; /* # of temp blocks written */
double blk_read_time; /* time spent reading blocks, in msec */
double blk_write_time; /* time spent writing blocks, in msec */
double temp_blk_read_time; /* time spent reading temp blocks, in msec */
double temp_blk_write_time; /* time spent writing temp blocks, in
* msec */
double usage; /* usage factor */
int64 wal_records; /* # of WAL records generated */
int64 wal_fpi; /* # of WAL full page images generated */
uint64 wal_bytes; /* total amount of WAL generated in bytes */
int64 jit_functions; /* total number of JIT functions emitted */
double jit_generation_time; /* total time to generate jit code */
int64 jit_inlining_count; /* number of times inlining time has been
* > 0 */
double jit_inlining_time; /* total time to inline jit code */
int64 jit_optimization_count; /* number of times optimization time
* has been > 0 */
double jit_optimization_time; /* total time to optimize jit code */
int64 jit_emission_count; /* number of times emission time has been
* > 0 */
double jit_emission_time; /* total time to emit jit code */
} Counters;
/*
* Global statistics for pg_stat_statements
*/
typedef struct pgssGlobalStats
{
int64 dealloc; /* # of times entries were deallocated */
TimestampTz stats_reset; /* timestamp with all stats reset */
} pgssGlobalStats;
/*
* Statistics per statement
*
* Note: in event of a failure in garbage collection of the query text file,
* we reset query_offset to zero and query_len to -1. This will be seen as
* an invalid state by qtext_fetch().
*/
typedef struct pgssEntry
{
pgssHashKey key; /* hash key of entry - MUST BE FIRST */
Counters counters; /* the statistics for this query */
Size query_offset; /* query text offset in external file */
int query_len; /* # of valid bytes in query string, or -1 */
int encoding; /* query text encoding */
slock_t mutex; /* protects the counters only */
} pgssEntry;
/*
* Global shared state
*/
typedef struct pgssSharedState
{
LWLock *lock; /* protects hashtable search/modification */
double cur_median_usage; /* current median usage in hashtable */
Size mean_query_len; /* current mean entry text length */
slock_t mutex; /* protects following fields only: */
Size extent; /* current extent of query file */
int n_writers; /* number of active writers to query file */
int gc_count; /* query file garbage collection cycle count */
pgssGlobalStats stats; /* global statistics for pgss */
} pgssSharedState;
/*---- Local variables ----*/
/* Current nesting depth of ExecutorRun+ProcessUtility calls */
static int exec_nested_level = 0;
/* Current nesting depth of planner calls */
static int plan_nested_level = 0;
/* Saved hook values in case of unload */
static shmem_request_hook_type prev_shmem_request_hook = NULL;
static shmem_startup_hook_type prev_shmem_startup_hook = NULL;
static post_parse_analyze_hook_type prev_post_parse_analyze_hook = NULL;
static planner_hook_type prev_planner_hook = NULL;
static ExecutorStart_hook_type prev_ExecutorStart = NULL;
static ExecutorRun_hook_type prev_ExecutorRun = NULL;
static ExecutorFinish_hook_type prev_ExecutorFinish = NULL;
static ExecutorEnd_hook_type prev_ExecutorEnd = NULL;
static ProcessUtility_hook_type prev_ProcessUtility = NULL;
/* Links to shared memory state */
static pgssSharedState *pgss = NULL;
static HTAB *pgss_hash = NULL;
/*---- GUC variables ----*/
typedef enum
{
PGSS_TRACK_NONE, /* track no statements */
PGSS_TRACK_TOP, /* only top level statements */
PGSS_TRACK_ALL /* all statements, including nested ones */
} PGSSTrackLevel;
static const struct config_enum_entry track_options[] =
{
{"none", PGSS_TRACK_NONE, false},
{"top", PGSS_TRACK_TOP, false},
{"all", PGSS_TRACK_ALL, false},
{NULL, 0, false}
};
static int pgss_max; /* max # statements to track */
static int pgss_track; /* tracking level */
static bool pgss_track_utility; /* whether to track utility commands */
static bool pgss_track_planning; /* whether to track planning duration */
static bool pgss_save; /* whether to save stats across shutdown */
#define pgss_enabled(level) \
(!IsParallelWorker() && \
(pgss_track == PGSS_TRACK_ALL || \
(pgss_track == PGSS_TRACK_TOP && (level) == 0)))
#define record_gc_qtexts() \
do { \
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; \
SpinLockAcquire(&s->mutex); \
s->gc_count++; \
SpinLockRelease(&s->mutex); \
} while(0)
/*---- Function declarations ----*/
void _PG_init(void);
PG_FUNCTION_INFO_V1(pg_stat_statements_reset);
PG_FUNCTION_INFO_V1(pg_stat_statements_reset_1_7);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_2);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_3);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_8);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_9);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_10);
PG_FUNCTION_INFO_V1(pg_stat_statements);
PG_FUNCTION_INFO_V1(pg_stat_statements_info);
static void pgss_shmem_request(void);
static void pgss_shmem_startup(void);
static void pgss_shmem_shutdown(int code, Datum arg);
static void pgss_post_parse_analyze(ParseState *pstate, Query *query,
JumbleState *jstate);
static PlannedStmt *pgss_planner(Query *parse,
const char *query_string,
int cursorOptions,
ParamListInfo boundParams);
static void pgss_ExecutorStart(QueryDesc *queryDesc, int eflags);
static void pgss_ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction,
uint64 count, bool execute_once);
static void pgss_ExecutorFinish(QueryDesc *queryDesc);
static void pgss_ExecutorEnd(QueryDesc *queryDesc);
static void pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
bool readOnlyTree,
ProcessUtilityContext context, ParamListInfo params,
QueryEnvironment *queryEnv,
DestReceiver *dest, QueryCompletion *qc);
static void pgss_store(const char *query, uint64 queryId,
int query_location, int query_len,
pgssStoreKind kind,
double total_time, uint64 rows,
const BufferUsage *bufusage,
const WalUsage *walusage,
const struct JitInstrumentation *jitusage,
JumbleState *jstate);
static void pg_stat_statements_internal(FunctionCallInfo fcinfo,
pgssVersion api_version,
bool showtext);
static Size pgss_memsize(void);
static pgssEntry *entry_alloc(pgssHashKey *key, Size query_offset, int query_len,
int encoding, bool sticky);
static void entry_dealloc(void);
static bool qtext_store(const char *query, int query_len,
Size *query_offset, int *gc_count);
static char *qtext_load_file(Size *buffer_size);
static char *qtext_fetch(Size query_offset, int query_len,
char *buffer, Size buffer_size);
static bool need_gc_qtexts(void);
static void gc_qtexts(void);
static void entry_reset(Oid userid, Oid dbid, uint64 queryid);
static char *generate_normalized_query(JumbleState *jstate, const char *query,
int query_loc, int *query_len_p);
static void fill_in_constant_lengths(JumbleState *jstate, const char *query,
int query_loc);
static int comp_location(const void *a, const void *b);
/*
* Module load callback
*/
void
_PG_init(void)
{
/*
* In order to create our shared memory area, we have to be loaded via
* shared_preload_libraries. If not, fall out without hooking into any of
* the main system. (We don't throw error here because it seems useful to
* allow the pg_stat_statements functions to be created even when the
* module isn't active. The functions must protect themselves against
* being called then, however.)
*/
if (!process_shared_preload_libraries_in_progress)
return;
/*
* Inform the postmaster that we want to enable query_id calculation if
* compute_query_id is set to auto.
*/
EnableQueryId();
/*
* Define (or redefine) custom GUC variables.
*/
DefineCustomIntVariable("pg_stat_statements.max",
"Sets the maximum number of statements tracked by pg_stat_statements.",
NULL,
&pgss_max,
5000,
100,
INT_MAX / 2,
PGC_POSTMASTER,
0,
NULL,
NULL,
NULL);
DefineCustomEnumVariable("pg_stat_statements.track",
"Selects which statements are tracked by pg_stat_statements.",
NULL,
&pgss_track,
PGSS_TRACK_TOP,
track_options,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_stat_statements.track_utility",
"Selects whether utility commands are tracked by pg_stat_statements.",
NULL,
&pgss_track_utility,
true,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_stat_statements.track_planning",
"Selects whether planning duration is tracked by pg_stat_statements.",
NULL,
&pgss_track_planning,
false,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_stat_statements.save",
"Save pg_stat_statements statistics across server shutdowns.",
NULL,
&pgss_save,
true,
PGC_SIGHUP,
0,
NULL,
NULL,
NULL);
MarkGUCPrefixReserved("pg_stat_statements");
/*
* Install hooks.
*/
prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = pgss_shmem_request;
prev_shmem_startup_hook = shmem_startup_hook;
shmem_startup_hook = pgss_shmem_startup;
prev_post_parse_analyze_hook = post_parse_analyze_hook;
post_parse_analyze_hook = pgss_post_parse_analyze;
prev_planner_hook = planner_hook;
planner_hook = pgss_planner;
prev_ExecutorStart = ExecutorStart_hook;
ExecutorStart_hook = pgss_ExecutorStart;
prev_ExecutorRun = ExecutorRun_hook;
ExecutorRun_hook = pgss_ExecutorRun;
prev_ExecutorFinish = ExecutorFinish_hook;
ExecutorFinish_hook = pgss_ExecutorFinish;
prev_ExecutorEnd = ExecutorEnd_hook;
ExecutorEnd_hook = pgss_ExecutorEnd;
prev_ProcessUtility = ProcessUtility_hook;
ProcessUtility_hook = pgss_ProcessUtility;
}
/*
* shmem_request hook: request additional shared resources. We'll allocate or
* attach to the shared resources in pgss_shmem_startup().
*/
static void
pgss_shmem_request(void)
{
if (prev_shmem_request_hook)
prev_shmem_request_hook();
RequestAddinShmemSpace(pgss_memsize());
RequestNamedLWLockTranche("pg_stat_statements", 1);
}
/*
* shmem_startup hook: allocate or attach to shared memory,
* then load any pre-existing statistics from file.
* Also create and load the query-texts file, which is expected to exist
* (even if empty) while the module is enabled.
*/
static void
pgss_shmem_startup(void)
{
bool found;
HASHCTL info;
FILE *file = NULL;
FILE *qfile = NULL;
uint32 header;
int32 num;
int32 pgver;
int32 i;
int buffer_size;
char *buffer = NULL;
if (prev_shmem_startup_hook)
prev_shmem_startup_hook();
/* reset in case this is a restart within the postmaster */
pgss = NULL;
pgss_hash = NULL;
/*
* Create or attach to the shared memory state, including hash table
*/
LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
pgss = ShmemInitStruct("pg_stat_statements",
sizeof(pgssSharedState),
&found);
if (!found)
{
/* First time through ... */
pgss->lock = &(GetNamedLWLockTranche("pg_stat_statements"))->lock;
pgss->cur_median_usage = ASSUMED_MEDIAN_INIT;
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
SpinLockInit(&pgss->mutex);
pgss->extent = 0;
pgss->n_writers = 0;
pgss->gc_count = 0;
pgss->stats.dealloc = 0;
pgss->stats.stats_reset = GetCurrentTimestamp();
}
info.keysize = sizeof(pgssHashKey);
info.entrysize = sizeof(pgssEntry);
pgss_hash = ShmemInitHash("pg_stat_statements hash",
pgss_max, pgss_max,
&info,
HASH_ELEM | HASH_BLOBS);
LWLockRelease(AddinShmemInitLock);
/*
* If we're in the postmaster (or a standalone backend...), set up a shmem
* exit hook to dump the statistics to disk.
*/
if (!IsUnderPostmaster)
on_shmem_exit(pgss_shmem_shutdown, (Datum) 0);
/*
* Done if some other process already completed our initialization.
*/
if (found)
return;
/*
* Note: we don't bother with locks here, because there should be no other
* processes running when this code is reached.
*/
/* Unlink query text file possibly left over from crash */
unlink(PGSS_TEXT_FILE);
/* Allocate new query text temp file */
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
goto write_error;
/*
* If we were told not to load old statistics, we're done. (Note we do
* not try to unlink any old dump file in this case. This seems a bit
* questionable but it's the historical behavior.)
*/
if (!pgss_save)
{
FreeFile(qfile);
return;
}
/*
* Attempt to load old statistics from the dump file.
*/
file = AllocateFile(PGSS_DUMP_FILE, PG_BINARY_R);
if (file == NULL)
{
if (errno != ENOENT)
goto read_error;
/* No existing persisted stats file, so we're done */
FreeFile(qfile);
return;
}
buffer_size = 2048;
buffer = (char *) palloc(buffer_size);
if (fread(&header, sizeof(uint32), 1, file) != 1 ||
fread(&pgver, sizeof(uint32), 1, file) != 1 ||
fread(&num, sizeof(int32), 1, file) != 1)
goto read_error;
if (header != PGSS_FILE_HEADER ||
pgver != PGSS_PG_MAJOR_VERSION)
goto data_error;
for (i = 0; i < num; i++)
{
pgssEntry temp;
pgssEntry *entry;
Size query_offset;
if (fread(&temp, sizeof(pgssEntry), 1, file) != 1)
goto read_error;
/* Encoding is the only field we can easily sanity-check */
if (!PG_VALID_BE_ENCODING(temp.encoding))
goto data_error;
/* Resize buffer as needed */
if (temp.query_len >= buffer_size)
{
buffer_size = Max(buffer_size * 2, temp.query_len + 1);
buffer = repalloc(buffer, buffer_size);
}
if (fread(buffer, 1, temp.query_len + 1, file) != temp.query_len + 1)
goto read_error;
/* Should have a trailing null, but let's make sure */
buffer[temp.query_len] = '\0';
/* Skip loading "sticky" entries */
if (IS_STICKY(temp.counters))
continue;
/* Store the query text */
query_offset = pgss->extent;
if (fwrite(buffer, 1, temp.query_len + 1, qfile) != temp.query_len + 1)
goto write_error;
pgss->extent += temp.query_len + 1;
/* make the hashtable entry (discards old entries if too many) */
entry = entry_alloc(&temp.key, query_offset, temp.query_len,
temp.encoding,
false);
/* copy in the actual stats */
entry->counters = temp.counters;
}
/* Read global statistics for pg_stat_statements */
if (fread(&pgss->stats, sizeof(pgssGlobalStats), 1, file) != 1)
goto read_error;
pfree(buffer);
FreeFile(file);
FreeFile(qfile);
/*
* Remove the persisted stats file so it's not included in
* backups/replication standbys, etc. A new file will be written on next
* shutdown.
*
* Note: it's okay if the PGSS_TEXT_FILE is included in a basebackup,
* because we remove that file on startup; it acts inversely to
* PGSS_DUMP_FILE, in that it is only supposed to be around when the
* server is running, whereas PGSS_DUMP_FILE is only supposed to be around
* when the server is not running. Leaving the file creates no danger of
* a newly restored database having a spurious record of execution costs,
* which is what we're really concerned about here.
*/
unlink(PGSS_DUMP_FILE);
return;
read_error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": %m",
PGSS_DUMP_FILE)));
goto fail;
data_error:
ereport(LOG,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("ignoring invalid data in file \"%s\"",
PGSS_DUMP_FILE)));
goto fail;
write_error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
fail:
if (buffer)
pfree(buffer);
if (file)
FreeFile(file);
if (qfile)
FreeFile(qfile);
/* If possible, throw away the bogus file; ignore any error */
unlink(PGSS_DUMP_FILE);
/*
* Don't unlink PGSS_TEXT_FILE here; it should always be around while the
* server is running with pg_stat_statements enabled
*/
}
/*
* shmem_shutdown hook: Dump statistics into file.
*
* Note: we don't bother with acquiring lock, because there should be no
* other processes running when this is called.
*/
static void
pgss_shmem_shutdown(int code, Datum arg)
{
FILE *file;
char *qbuffer = NULL;
Size qbuffer_size = 0;
HASH_SEQ_STATUS hash_seq;
int32 num_entries;
pgssEntry *entry;
/* Don't try to dump during a crash. */
if (code)
return;
/* Safety check ... shouldn't get here unless shmem is set up. */
if (!pgss || !pgss_hash)
return;
/* Don't dump if told not to. */
if (!pgss_save)
return;
file = AllocateFile(PGSS_DUMP_FILE ".tmp", PG_BINARY_W);
if (file == NULL)
goto error;
if (fwrite(&PGSS_FILE_HEADER, sizeof(uint32), 1, file) != 1)
goto error;
if (fwrite(&PGSS_PG_MAJOR_VERSION, sizeof(uint32), 1, file) != 1)
goto error;
num_entries = hash_get_num_entries(pgss_hash);
if (fwrite(&num_entries, sizeof(int32), 1, file) != 1)
goto error;
qbuffer = qtext_load_file(&qbuffer_size);
if (qbuffer == NULL)
goto error;
/*
* When serializing to disk, we store query texts immediately after their
* entry data. Any orphaned query texts are thereby excluded.
*/
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
int len = entry->query_len;
char *qstr = qtext_fetch(entry->query_offset, len,
qbuffer, qbuffer_size);
if (qstr == NULL)
continue; /* Ignore any entries with bogus texts */
if (fwrite(entry, sizeof(pgssEntry), 1, file) != 1 ||
fwrite(qstr, 1, len + 1, file) != len + 1)
{
/* note: we assume hash_seq_term won't change errno */
hash_seq_term(&hash_seq);
goto error;
}
}
/* Dump global statistics for pg_stat_statements */
if (fwrite(&pgss->stats, sizeof(pgssGlobalStats), 1, file) != 1)
goto error;
free(qbuffer);
qbuffer = NULL;
if (FreeFile(file))
{
file = NULL;
goto error;
}
/*
* Rename file into place, so we atomically replace any old one.
*/
(void) durable_rename(PGSS_DUMP_FILE ".tmp", PGSS_DUMP_FILE, LOG);
/* Unlink query-texts file; it's not needed while shutdown */
unlink(PGSS_TEXT_FILE);
return;
error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_DUMP_FILE ".tmp")));
if (qbuffer)
free(qbuffer);
if (file)
FreeFile(file);
unlink(PGSS_DUMP_FILE ".tmp");
unlink(PGSS_TEXT_FILE);
}
/*
* Post-parse-analysis hook: mark query with a queryId
*/
static void
pgss_post_parse_analyze(ParseState *pstate, Query *query, JumbleState *jstate)
{
if (prev_post_parse_analyze_hook)
prev_post_parse_analyze_hook(pstate, query, jstate);
/* Safety check... */
if (!pgss || !pgss_hash || !pgss_enabled(exec_nested_level))
return;
/*
* Clear queryId for prepared statements related utility, as those will
* inherit from the underlying statement's one (except DEALLOCATE which is
* entirely untracked).
*/
if (query->utilityStmt)
{
if (pgss_track_utility && !PGSS_HANDLED_UTILITY(query->utilityStmt))
query->queryId = UINT64CONST(0);
return;
}
/*
* If query jumbling were able to identify any ignorable constants, we
* immediately create a hash table entry for the query, so that we can
* record the normalized form of the query string. If there were no such
* constants, the normalized string would be the same as the query text
* anyway, so there's no need for an early entry.
*/
if (jstate && jstate->clocations_count > 0)
pgss_store(pstate->p_sourcetext,
query->queryId,
query->stmt_location,
query->stmt_len,
PGSS_INVALID,
0,
0,
NULL,
NULL,
NULL,
jstate);
}
/*
* Planner hook: forward to regular planner, but measure planning time
* if needed.
*/
static PlannedStmt *
pgss_planner(Query *parse,
const char *query_string,
int cursorOptions,
ParamListInfo boundParams)
{
PlannedStmt *result;
/*
* We can't process the query if no query_string is provided, as
* pgss_store needs it. We also ignore query without queryid, as it would
* be treated as a utility statement, which may not be the case.
*
* Note that planner_hook can be called from the planner itself, so we
* have a specific nesting level for the planner. However, utility
* commands containing optimizable statements can also call the planner,
* same for regular DML (for instance for underlying foreign key queries).
* So testing the planner nesting level only is not enough to detect real
* top level planner call.
*/
if (pgss_enabled(plan_nested_level + exec_nested_level)
&& pgss_track_planning && query_string
&& parse->queryId != UINT64CONST(0))
{
instr_time start;
instr_time duration;
BufferUsage bufusage_start,
bufusage;
WalUsage walusage_start,
walusage;
/* We need to track buffer usage as the planner can access them. */
bufusage_start = pgBufferUsage;
/*
* Similarly the planner could write some WAL records in some cases
* (e.g. setting a hint bit with those being WAL-logged)
*/
walusage_start = pgWalUsage;
INSTR_TIME_SET_CURRENT(start);
plan_nested_level++;
PG_TRY();
{
if (prev_planner_hook)
result = prev_planner_hook(parse, query_string, cursorOptions,
boundParams);
else
result = standard_planner(parse, query_string, cursorOptions,
boundParams);
}
PG_FINALLY();
{
plan_nested_level--;
}
PG_END_TRY();
INSTR_TIME_SET_CURRENT(duration);
INSTR_TIME_SUBTRACT(duration, start);
/* calc differences of buffer counters. */
memset(&bufusage, 0, sizeof(BufferUsage));
BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
/* calc differences of WAL counters. */
memset(&walusage, 0, sizeof(WalUsage));
WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start);
pgss_store(query_string,
parse->queryId,
parse->stmt_location,
parse->stmt_len,
PGSS_PLAN,
INSTR_TIME_GET_MILLISEC(duration),
0,
&bufusage,
&walusage,
NULL,
NULL);
}
else
{
if (prev_planner_hook)
result = prev_planner_hook(parse, query_string, cursorOptions,
boundParams);
else
result = standard_planner(parse, query_string, cursorOptions,
boundParams);
}
return result;
}
/*
* ExecutorStart hook: start up tracking if needed
*/
static void
pgss_ExecutorStart(QueryDesc *queryDesc, int eflags)
{
if (prev_ExecutorStart)
prev_ExecutorStart(queryDesc, eflags);
else
standard_ExecutorStart(queryDesc, eflags);
/*
* If query has queryId zero, don't track it. This prevents double
* counting of optimizable statements that are directly contained in
* utility statements.
*/
if (pgss_enabled(exec_nested_level) && queryDesc->plannedstmt->queryId != UINT64CONST(0))
{
/*
* Set up to track total elapsed time in ExecutorRun. Make sure the
* space is allocated in the per-query context so it will go away at
* ExecutorEnd.
*/
if (queryDesc->totaltime == NULL)
{
MemoryContext oldcxt;
oldcxt = MemoryContextSwitchTo(queryDesc->estate->es_query_cxt);
queryDesc->totaltime = InstrAlloc(1, INSTRUMENT_ALL, false);
MemoryContextSwitchTo(oldcxt);
}
}
}
/*
* ExecutorRun hook: all we need do is track nesting depth
*/
static void
pgss_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction, uint64 count,
bool execute_once)
{
exec_nested_level++;
PG_TRY();
{
if (prev_ExecutorRun)
prev_ExecutorRun(queryDesc, direction, count, execute_once);
else
standard_ExecutorRun(queryDesc, direction, count, execute_once);
}
PG_FINALLY();
{
exec_nested_level--;
}
PG_END_TRY();
}
/*
* ExecutorFinish hook: all we need do is track nesting depth
*/
static void
pgss_ExecutorFinish(QueryDesc *queryDesc)
{
exec_nested_level++;
PG_TRY();
{
if (prev_ExecutorFinish)
prev_ExecutorFinish(queryDesc);
else
standard_ExecutorFinish(queryDesc);
}
PG_FINALLY();
{
exec_nested_level--;
}
PG_END_TRY();
}
/*
* ExecutorEnd hook: store results if needed
*/
static void
pgss_ExecutorEnd(QueryDesc *queryDesc)
{
uint64 queryId = queryDesc->plannedstmt->queryId;
if (queryId != UINT64CONST(0) && queryDesc->totaltime &&
pgss_enabled(exec_nested_level))
{
/*
* Make sure stats accumulation is done. (Note: it's okay if several
* levels of hook all do this.)
*/
InstrEndLoop(queryDesc->totaltime);
pgss_store(queryDesc->sourceText,
queryId,
queryDesc->plannedstmt->stmt_location,
queryDesc->plannedstmt->stmt_len,
PGSS_EXEC,
queryDesc->totaltime->total * 1000.0, /* convert to msec */
queryDesc->estate->es_processed,
&queryDesc->totaltime->bufusage,
&queryDesc->totaltime->walusage,
queryDesc->estate->es_jit ? &queryDesc->estate->es_jit->instr : NULL,
NULL);
}
if (prev_ExecutorEnd)
prev_ExecutorEnd(queryDesc);
else
standard_ExecutorEnd(queryDesc);
}
/*
* ProcessUtility hook
*/
static void
pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
bool readOnlyTree,
ProcessUtilityContext context,
ParamListInfo params, QueryEnvironment *queryEnv,
DestReceiver *dest, QueryCompletion *qc)
{
Node *parsetree = pstmt->utilityStmt;
uint64 saved_queryId = pstmt->queryId;
int saved_stmt_location = pstmt->stmt_location;
int saved_stmt_len = pstmt->stmt_len;
/*
* Force utility statements to get queryId zero. We do this even in cases
* where the statement contains an optimizable statement for which a
* queryId could be derived (such as EXPLAIN or DECLARE CURSOR). For such
* cases, runtime control will first go through ProcessUtility and then
* the executor, and we don't want the executor hooks to do anything,
* since we are already measuring the statement's costs at the utility
* level.
*
* Note that this is only done if pg_stat_statements is enabled and
* configured to track utility statements, in the unlikely possibility
* that user configured another extension to handle utility statements
* only.
*/
if (pgss_enabled(exec_nested_level) && pgss_track_utility)
pstmt->queryId = UINT64CONST(0);
/*
* If it's an EXECUTE statement, we don't track it and don't increment the
* nesting level. This allows the cycles to be charged to the underlying
* PREPARE instead (by the Executor hooks), which is much more useful.
*
* We also don't track execution of PREPARE. If we did, we would get one
* hash table entry for the PREPARE (with hash calculated from the query
* string), and then a different one with the same query string (but hash
* calculated from the query tree) would be used to accumulate costs of
* ensuing EXECUTEs. This would be confusing, and inconsistent with other
* cases where planning time is not included at all.
*
* Likewise, we don't track execution of DEALLOCATE.
*/
if (pgss_track_utility && pgss_enabled(exec_nested_level) &&
PGSS_HANDLED_UTILITY(parsetree))
{
instr_time start;
instr_time duration;
uint64 rows;
BufferUsage bufusage_start,
bufusage;
WalUsage walusage_start,
walusage;
bufusage_start = pgBufferUsage;
walusage_start = pgWalUsage;
INSTR_TIME_SET_CURRENT(start);
exec_nested_level++;
PG_TRY();
{
if (prev_ProcessUtility)
prev_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
else
standard_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
}
PG_FINALLY();
{
exec_nested_level--;
}
PG_END_TRY();
/*
* CAUTION: do not access the *pstmt data structure again below here.
* If it was a ROLLBACK or similar, that data structure may have been
* freed. We must copy everything we still need into local variables,
* which we did above.
*
* For the same reason, we can't risk restoring pstmt->queryId to its
* former value, which'd otherwise be a good idea.
*/
INSTR_TIME_SET_CURRENT(duration);
INSTR_TIME_SUBTRACT(duration, start);
/*
* Track the total number of rows retrieved or affected by the utility
* statements of COPY, FETCH, CREATE TABLE AS, CREATE MATERIALIZED
* VIEW, REFRESH MATERIALIZED VIEW and SELECT INTO.
*/
rows = (qc && (qc->commandTag == CMDTAG_COPY ||
qc->commandTag == CMDTAG_FETCH ||
qc->commandTag == CMDTAG_SELECT ||
qc->commandTag == CMDTAG_REFRESH_MATERIALIZED_VIEW)) ?
qc->nprocessed : 0;
/* calc differences of buffer counters. */
memset(&bufusage, 0, sizeof(BufferUsage));
BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
/* calc differences of WAL counters. */
memset(&walusage, 0, sizeof(WalUsage));
WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start);
pgss_store(queryString,
saved_queryId,
saved_stmt_location,
saved_stmt_len,
PGSS_EXEC,
INSTR_TIME_GET_MILLISEC(duration),
rows,
&bufusage,
&walusage,
NULL,
NULL);
}
else
{
if (prev_ProcessUtility)
prev_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
else
standard_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
}
}
/*
* Store some statistics for a statement.
*
* If jstate is not NULL then we're trying to create an entry for which
* we have no statistics as yet; we just want to record the normalized
* query string. total_time, rows, bufusage and walusage are ignored in this
* case.
*
* If kind is PGSS_PLAN or PGSS_EXEC, its value is used as the array position
* for the arrays in the Counters field.
*/
static void
pgss_store(const char *query, uint64 queryId,
int query_location, int query_len,
pgssStoreKind kind,
double total_time, uint64 rows,
const BufferUsage *bufusage,
const WalUsage *walusage,
const struct JitInstrumentation *jitusage,
JumbleState *jstate)
{
pgssHashKey key;
pgssEntry *entry;
char *norm_query = NULL;
int encoding = GetDatabaseEncoding();
Assert(query != NULL);
/* Safety check... */
if (!pgss || !pgss_hash)
return;
/*
* Nothing to do if compute_query_id isn't enabled and no other module
* computed a query identifier.
*/
if (queryId == UINT64CONST(0))
return;
/*
* Confine our attention to the relevant part of the string, if the query
* is a portion of a multi-statement source string, and update query
* location and length if needed.
*/
query = CleanQuerytext(query, &query_location, &query_len);
/* Set up key for hashtable search */
/* memset() is required when pgssHashKey is without padding only */
memset(&key, 0, sizeof(pgssHashKey));
key.userid = GetUserId();
key.dbid = MyDatabaseId;
key.queryid = queryId;
key.toplevel = (exec_nested_level == 0);
/* Lookup the hash table entry with shared lock. */
LWLockAcquire(pgss->lock, LW_SHARED);
entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_FIND, NULL);
/* Create new entry, if not present */
if (!entry)
{
Size query_offset;
int gc_count;
bool stored;
bool do_gc;
/*
* Create a new, normalized query string if caller asked. We don't
* need to hold the lock while doing this work. (Note: in any case,
* it's possible that someone else creates a duplicate hashtable entry
* in the interval where we don't hold the lock below. That case is
* handled by entry_alloc.)
*/
if (jstate)
{
LWLockRelease(pgss->lock);
norm_query = generate_normalized_query(jstate, query,
query_location,
&query_len);
LWLockAcquire(pgss->lock, LW_SHARED);
}
/* Append new query text to file with only shared lock held */
stored = qtext_store(norm_query ? norm_query : query, query_len,
&query_offset, &gc_count);
/*
* Determine whether we need to garbage collect external query texts
* while the shared lock is still held. This micro-optimization
* avoids taking the time to decide this while holding exclusive lock.
*/
do_gc = need_gc_qtexts();
/* Need exclusive lock to make a new hashtable entry - promote */
LWLockRelease(pgss->lock);
LWLockAcquire(pgss->lock, LW_EXCLUSIVE);
/*
* A garbage collection may have occurred while we weren't holding the
* lock. In the unlikely event that this happens, the query text we
* stored above will have been garbage collected, so write it again.
* This should be infrequent enough that doing it while holding
* exclusive lock isn't a performance problem.
*/
if (!stored || pgss->gc_count != gc_count)
stored = qtext_store(norm_query ? norm_query : query, query_len,
&query_offset, NULL);
/* If we failed to write to the text file, give up */
if (!stored)
goto done;
/* OK to create a new hashtable entry */
entry = entry_alloc(&key, query_offset, query_len, encoding,
jstate != NULL);
/* If needed, perform garbage collection while exclusive lock held */
if (do_gc)
gc_qtexts();
}
/* Increment the counts, except when jstate is not NULL */
if (!jstate)
{
/*
* Grab the spinlock while updating the counters (see comment about
* locking rules at the head of the file)
*/
volatile pgssEntry *e = (volatile pgssEntry *) entry;
Assert(kind == PGSS_PLAN || kind == PGSS_EXEC);
SpinLockAcquire(&e->mutex);
/* "Unstick" entry if it was previously sticky */
if (IS_STICKY(e->counters))
e->counters.usage = USAGE_INIT;
e->counters.calls[kind] += 1;
e->counters.total_time[kind] += total_time;
if (e->counters.calls[kind] == 1)
{
e->counters.min_time[kind] = total_time;
e->counters.max_time[kind] = total_time;
e->counters.mean_time[kind] = total_time;
}
else
{
/*
* Welford's method for accurately computing variance. See
* <http://www.johndcook.com/blog/standard_deviation/>
*/
double old_mean = e->counters.mean_time[kind];
e->counters.mean_time[kind] +=
(total_time - old_mean) / e->counters.calls[kind];
e->counters.sum_var_time[kind] +=
(total_time - old_mean) * (total_time - e->counters.mean_time[kind]);
/* calculate min and max time */
if (e->counters.min_time[kind] > total_time)
e->counters.min_time[kind] = total_time;
if (e->counters.max_time[kind] < total_time)
e->counters.max_time[kind] = total_time;
}
e->counters.rows += rows;
e->counters.shared_blks_hit += bufusage->shared_blks_hit;
e->counters.shared_blks_read += bufusage->shared_blks_read;
e->counters.shared_blks_dirtied += bufusage->shared_blks_dirtied;
e->counters.shared_blks_written += bufusage->shared_blks_written;
e->counters.local_blks_hit += bufusage->local_blks_hit;
e->counters.local_blks_read += bufusage->local_blks_read;
e->counters.local_blks_dirtied += bufusage->local_blks_dirtied;
e->counters.local_blks_written += bufusage->local_blks_written;
e->counters.temp_blks_read += bufusage->temp_blks_read;
e->counters.temp_blks_written += bufusage->temp_blks_written;
e->counters.blk_read_time += INSTR_TIME_GET_MILLISEC(bufusage->blk_read_time);
e->counters.blk_write_time += INSTR_TIME_GET_MILLISEC(bufusage->blk_write_time);
e->counters.temp_blk_read_time += INSTR_TIME_GET_MILLISEC(bufusage->temp_blk_read_time);
e->counters.temp_blk_write_time += INSTR_TIME_GET_MILLISEC(bufusage->temp_blk_write_time);
e->counters.usage += USAGE_EXEC(total_time);
e->counters.wal_records += walusage->wal_records;
e->counters.wal_fpi += walusage->wal_fpi;
e->counters.wal_bytes += walusage->wal_bytes;
if (jitusage)
{
e->counters.jit_functions += jitusage->created_functions;
e->counters.jit_generation_time += INSTR_TIME_GET_MILLISEC(jitusage->generation_counter);
if (INSTR_TIME_GET_MILLISEC(jitusage->inlining_counter))
e->counters.jit_inlining_count++;
e->counters.jit_inlining_time += INSTR_TIME_GET_MILLISEC(jitusage->inlining_counter);
if (INSTR_TIME_GET_MILLISEC(jitusage->optimization_counter))
e->counters.jit_optimization_count++;
e->counters.jit_optimization_time += INSTR_TIME_GET_MILLISEC(jitusage->optimization_counter);
if (INSTR_TIME_GET_MILLISEC(jitusage->emission_counter))
e->counters.jit_emission_count++;
e->counters.jit_emission_time += INSTR_TIME_GET_MILLISEC(jitusage->emission_counter);
}
SpinLockRelease(&e->mutex);
}
done:
LWLockRelease(pgss->lock);
/* We postpone this clean-up until we're out of the lock */
if (norm_query)
pfree(norm_query);
}
/*
* Reset statement statistics corresponding to userid, dbid, and queryid.
*/
Datum
pg_stat_statements_reset_1_7(PG_FUNCTION_ARGS)
{
Oid userid;
Oid dbid;
uint64 queryid;
userid = PG_GETARG_OID(0);
dbid = PG_GETARG_OID(1);
queryid = (uint64) PG_GETARG_INT64(2);
entry_reset(userid, dbid, queryid);
PG_RETURN_VOID();
}
/*
* Reset statement statistics.
*/
Datum
pg_stat_statements_reset(PG_FUNCTION_ARGS)
{
entry_reset(0, 0, 0);
PG_RETURN_VOID();
}
/* Number of output arguments (columns) for various API versions */
#define PG_STAT_STATEMENTS_COLS_V1_0 14
#define PG_STAT_STATEMENTS_COLS_V1_1 18
#define PG_STAT_STATEMENTS_COLS_V1_2 19
#define PG_STAT_STATEMENTS_COLS_V1_3 23
#define PG_STAT_STATEMENTS_COLS_V1_8 32
#define PG_STAT_STATEMENTS_COLS_V1_9 33
#define PG_STAT_STATEMENTS_COLS_V1_10 43
#define PG_STAT_STATEMENTS_COLS 43 /* maximum of above */
/*
* Retrieve statement statistics.
*
* The SQL API of this function has changed multiple times, and will likely
* do so again in future. To support the case where a newer version of this
* loadable module is being used with an old SQL declaration of the function,
* we continue to support the older API versions. For 1.2 and later, the
* expected API version is identified by embedding it in the C name of the
* function. Unfortunately we weren't bright enough to do that for 1.1.
*/
Datum
pg_stat_statements_1_10(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_10, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_9(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_9, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_8(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_8, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_3(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_3, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_2(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_2, showtext);
return (Datum) 0;
}
/*
* Legacy entry point for pg_stat_statements() API versions 1.0 and 1.1.
* This can be removed someday, perhaps.
*/
Datum
pg_stat_statements(PG_FUNCTION_ARGS)
{
/* If it's really API 1.1, we'll figure that out below */
pg_stat_statements_internal(fcinfo, PGSS_V1_0, true);
return (Datum) 0;
}
/* Common code for all versions of pg_stat_statements() */
static void
pg_stat_statements_internal(FunctionCallInfo fcinfo,
pgssVersion api_version,
bool showtext)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
Oid userid = GetUserId();
bool is_allowed_role = false;
char *qbuffer = NULL;
Size qbuffer_size = 0;
Size extent = 0;
int gc_count = 0;
HASH_SEQ_STATUS hash_seq;
pgssEntry *entry;
/*
* Superusers or roles with the privileges of pg_read_all_stats members
* are allowed
*/
is_allowed_role = has_privs_of_role(userid, ROLE_PG_READ_ALL_STATS);
/* hash table must exist already */
if (!pgss || !pgss_hash)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));
InitMaterializedSRF(fcinfo, 0);
/*
* Check we have the expected number of output arguments. Aside from
* being a good safety check, we need a kluge here to detect API version
* 1.1, which was wedged into the code in an ill-considered way.
*/
switch (rsinfo->setDesc->natts)
{
case PG_STAT_STATEMENTS_COLS_V1_0:
if (api_version != PGSS_V1_0)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_1:
/* pg_stat_statements() should have told us 1.0 */
if (api_version != PGSS_V1_0)
elog(ERROR, "incorrect number of output arguments");
api_version = PGSS_V1_1;
break;
case PG_STAT_STATEMENTS_COLS_V1_2:
if (api_version != PGSS_V1_2)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_3:
if (api_version != PGSS_V1_3)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_8:
if (api_version != PGSS_V1_8)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_9:
if (api_version != PGSS_V1_9)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_10:
if (api_version != PGSS_V1_10)
elog(ERROR, "incorrect number of output arguments");
break;
default:
elog(ERROR, "incorrect number of output arguments");
}
/*
* We'd like to load the query text file (if needed) while not holding any
* lock on pgss->lock. In the worst case we'll have to do this again
* after we have the lock, but it's unlikely enough to make this a win
* despite occasional duplicated work. We need to reload if anybody
* writes to the file (either a retail qtext_store(), or a garbage
* collection) between this point and where we've gotten shared lock. If
* a qtext_store is actually in progress when we look, we might as well
* skip the speculative load entirely.
*/
if (showtext)
{
int n_writers;
/* Take the mutex so we can examine variables */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
extent = s->extent;
n_writers = s->n_writers;
gc_count = s->gc_count;
SpinLockRelease(&s->mutex);
}
/* No point in loading file now if there are active writers */
if (n_writers == 0)
qbuffer = qtext_load_file(&qbuffer_size);
}
/*
* Get shared lock, load or reload the query text file if we must, and
* iterate over the hashtable entries.
*
* With a large hash table, we might be holding the lock rather longer
* than one could wish. However, this only blocks creation of new hash
* table entries, and the larger the hash table the less likely that is to
* be needed. So we can hope this is okay. Perhaps someday we'll decide
* we need to partition the hash table to limit the time spent holding any
* one lock.
*/
LWLockAcquire(pgss->lock, LW_SHARED);
if (showtext)
{
/*
* Here it is safe to examine extent and gc_count without taking the
* mutex. Note that although other processes might change
* pgss->extent just after we look at it, the strings they then write
* into the file cannot yet be referenced in the hashtable, so we
* don't care whether we see them or not.
*
* If qtext_load_file fails, we just press on; we'll return NULL for
* every query text.
*/
if (qbuffer == NULL ||
pgss->extent != extent ||
pgss->gc_count != gc_count)
{
if (qbuffer)
free(qbuffer);
qbuffer = qtext_load_file(&qbuffer_size);
}
}
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
Datum values[PG_STAT_STATEMENTS_COLS];
bool nulls[PG_STAT_STATEMENTS_COLS];
int i = 0;
Counters tmp;
double stddev;
int64 queryid = entry->key.queryid;
memset(values, 0, sizeof(values));
memset(nulls, 0, sizeof(nulls));
values[i++] = ObjectIdGetDatum(entry->key.userid);
values[i++] = ObjectIdGetDatum(entry->key.dbid);
if (api_version >= PGSS_V1_9)
values[i++] = BoolGetDatum(entry->key.toplevel);
if (is_allowed_role || entry->key.userid == userid)
{
if (api_version >= PGSS_V1_2)
values[i++] = Int64GetDatumFast(queryid);
if (showtext)
{
char *qstr = qtext_fetch(entry->query_offset,
entry->query_len,
qbuffer,
qbuffer_size);
if (qstr)
{
char *enc;
enc = pg_any_to_server(qstr,
entry->query_len,
entry->encoding);
values[i++] = CStringGetTextDatum(enc);
if (enc != qstr)
pfree(enc);
}
else
{
/* Just return a null if we fail to find the text */
nulls[i++] = true;
}
}
else
{
/* Query text not requested */
nulls[i++] = true;
}
}
else
{
/* Don't show queryid */
if (api_version >= PGSS_V1_2)
nulls[i++] = true;
/*
* Don't show query text, but hint as to the reason for not doing
* so if it was requested
*/
if (showtext)
values[i++] = CStringGetTextDatum("<insufficient privilege>");
else
nulls[i++] = true;
}
/* copy counters to a local variable to keep locking time short */
{
volatile pgssEntry *e = (volatile pgssEntry *) entry;
SpinLockAcquire(&e->mutex);
tmp = e->counters;
SpinLockRelease(&e->mutex);
}
/* Skip entry if unexecuted (ie, it's a pending "sticky" entry) */
if (IS_STICKY(tmp))
continue;
/* Note that we rely on PGSS_PLAN being 0 and PGSS_EXEC being 1. */
for (int kind = 0; kind < PGSS_NUMKIND; kind++)
{
if (kind == PGSS_EXEC || api_version >= PGSS_V1_8)
{
values[i++] = Int64GetDatumFast(tmp.calls[kind]);
values[i++] = Float8GetDatumFast(tmp.total_time[kind]);
}
if ((kind == PGSS_EXEC && api_version >= PGSS_V1_3) ||
api_version >= PGSS_V1_8)
{
values[i++] = Float8GetDatumFast(tmp.min_time[kind]);
values[i++] = Float8GetDatumFast(tmp.max_time[kind]);
values[i++] = Float8GetDatumFast(tmp.mean_time[kind]);
/*
* Note we are calculating the population variance here, not
* the sample variance, as we have data for the whole
* population, so Bessel's correction is not used, and we
* don't divide by tmp.calls - 1.
*/
if (tmp.calls[kind] > 1)
stddev = sqrt(tmp.sum_var_time[kind] / tmp.calls[kind]);
else
stddev = 0.0;
values[i++] = Float8GetDatumFast(stddev);
}
}
values[i++] = Int64GetDatumFast(tmp.rows);
values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
if (api_version >= PGSS_V1_1)
values[i++] = Int64GetDatumFast(tmp.shared_blks_dirtied);
values[i++] = Int64GetDatumFast(tmp.shared_blks_written);
values[i++] = Int64GetDatumFast(tmp.local_blks_hit);
values[i++] = Int64GetDatumFast(tmp.local_blks_read);
if (api_version >= PGSS_V1_1)
values[i++] = Int64GetDatumFast(tmp.local_blks_dirtied);
values[i++] = Int64GetDatumFast(tmp.local_blks_written);
values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
if (api_version >= PGSS_V1_1)
{
values[i++] = Float8GetDatumFast(tmp.blk_read_time);
values[i++] = Float8GetDatumFast(tmp.blk_write_time);
}
if (api_version >= PGSS_V1_10)
{
values[i++] = Float8GetDatumFast(tmp.temp_blk_read_time);
values[i++] = Float8GetDatumFast(tmp.temp_blk_write_time);
}
if (api_version >= PGSS_V1_8)
{
char buf[256];
Datum wal_bytes;
values[i++] = Int64GetDatumFast(tmp.wal_records);
values[i++] = Int64GetDatumFast(tmp.wal_fpi);
snprintf(buf, sizeof buf, UINT64_FORMAT, tmp.wal_bytes);
/* Convert to numeric. */
wal_bytes = DirectFunctionCall3(numeric_in,
CStringGetDatum(buf),
ObjectIdGetDatum(0),
Int32GetDatum(-1));
values[i++] = wal_bytes;
}
if (api_version >= PGSS_V1_10)
{
values[i++] = Int64GetDatumFast(tmp.jit_functions);
values[i++] = Float8GetDatumFast(tmp.jit_generation_time);
values[i++] = Int64GetDatumFast(tmp.jit_inlining_count);
values[i++] = Float8GetDatumFast(tmp.jit_inlining_time);
values[i++] = Int64GetDatumFast(tmp.jit_optimization_count);
values[i++] = Float8GetDatumFast(tmp.jit_optimization_time);
values[i++] = Int64GetDatumFast(tmp.jit_emission_count);
values[i++] = Float8GetDatumFast(tmp.jit_emission_time);
}
Assert(i == (api_version == PGSS_V1_0 ? PG_STAT_STATEMENTS_COLS_V1_0 :
api_version == PGSS_V1_1 ? PG_STAT_STATEMENTS_COLS_V1_1 :
api_version == PGSS_V1_2 ? PG_STAT_STATEMENTS_COLS_V1_2 :
api_version == PGSS_V1_3 ? PG_STAT_STATEMENTS_COLS_V1_3 :
api_version == PGSS_V1_8 ? PG_STAT_STATEMENTS_COLS_V1_8 :
api_version == PGSS_V1_9 ? PG_STAT_STATEMENTS_COLS_V1_9 :
api_version == PGSS_V1_10 ? PG_STAT_STATEMENTS_COLS_V1_10 :
-1 /* fail if you forget to update this assert */ ));
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
}
LWLockRelease(pgss->lock);
if (qbuffer)
free(qbuffer);
}
/* Number of output arguments (columns) for pg_stat_statements_info */
#define PG_STAT_STATEMENTS_INFO_COLS 2
/*
* Return statistics of pg_stat_statements.
*/
Datum
pg_stat_statements_info(PG_FUNCTION_ARGS)
{
pgssGlobalStats stats;
TupleDesc tupdesc;
Datum values[PG_STAT_STATEMENTS_INFO_COLS];
bool nulls[PG_STAT_STATEMENTS_INFO_COLS];
if (!pgss || !pgss_hash)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
MemSet(values, 0, sizeof(values));
MemSet(nulls, 0, sizeof(nulls));
/* Read global statistics for pg_stat_statements */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
stats = s->stats;
SpinLockRelease(&s->mutex);
}
values[0] = Int64GetDatum(stats.dealloc);
values[1] = TimestampTzGetDatum(stats.stats_reset);
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}
/*
* Estimate shared memory space needed.
*/
static Size
pgss_memsize(void)
{
Size size;
size = MAXALIGN(sizeof(pgssSharedState));
size = add_size(size, hash_estimate_size(pgss_max, sizeof(pgssEntry)));
return size;
}
/*
* Allocate a new hashtable entry.
* caller must hold an exclusive lock on pgss->lock
*
* "query" need not be null-terminated; we rely on query_len instead
*
* If "sticky" is true, make the new entry artificially sticky so that it will
* probably still be there when the query finishes execution. We do this by
* giving it a median usage value rather than the normal value. (Strictly
* speaking, query strings are normalized on a best effort basis, though it
* would be difficult to demonstrate this even under artificial conditions.)
*
* Note: despite needing exclusive lock, it's not an error for the target
* entry to already exist. This is because pgss_store releases and
* reacquires lock after failing to find a match; so someone else could
* have made the entry while we waited to get exclusive lock.
*/
static pgssEntry *
entry_alloc(pgssHashKey *key, Size query_offset, int query_len, int encoding,
bool sticky)
{
pgssEntry *entry;
bool found;
/* Make space if needed */
while (hash_get_num_entries(pgss_hash) >= pgss_max)
entry_dealloc();
/* Find or create an entry with desired hash code */
entry = (pgssEntry *) hash_search(pgss_hash, key, HASH_ENTER, &found);
if (!found)
{
/* New entry, initialize it */
/* reset the statistics */
memset(&entry->counters, 0, sizeof(Counters));
/* set the appropriate initial usage count */
entry->counters.usage = sticky ? pgss->cur_median_usage : USAGE_INIT;
/* re-initialize the mutex each time ... we assume no one using it */
SpinLockInit(&entry->mutex);
/* ... and don't forget the query text metadata */
Assert(query_len >= 0);
entry->query_offset = query_offset;
entry->query_len = query_len;
entry->encoding = encoding;
}
return entry;
}
/*
* qsort comparator for sorting into increasing usage order
*/
static int
entry_cmp(const void *lhs, const void *rhs)
{
double l_usage = (*(pgssEntry *const *) lhs)->counters.usage;
double r_usage = (*(pgssEntry *const *) rhs)->counters.usage;
if (l_usage < r_usage)
return -1;
else if (l_usage > r_usage)
return +1;
else
return 0;
}
/*
* Deallocate least-used entries.
*
* Caller must hold an exclusive lock on pgss->lock.
*/
static void
entry_dealloc(void)
{
HASH_SEQ_STATUS hash_seq;
pgssEntry **entries;
pgssEntry *entry;
int nvictims;
int i;
Size tottextlen;
int nvalidtexts;
/*
* Sort entries by usage and deallocate USAGE_DEALLOC_PERCENT of them.
* While we're scanning the table, apply the decay factor to the usage
* values, and update the mean query length.
*
* Note that the mean query length is almost immediately obsolete, since
* we compute it before not after discarding the least-used entries.
* Hopefully, that doesn't affect the mean too much; it doesn't seem worth
* making two passes to get a more current result. Likewise, the new
* cur_median_usage includes the entries we're about to zap.
*/
entries = palloc(hash_get_num_entries(pgss_hash) * sizeof(pgssEntry *));
i = 0;
tottextlen = 0;
nvalidtexts = 0;
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
entries[i++] = entry;
/* "Sticky" entries get a different usage decay rate. */
if (IS_STICKY(entry->counters))
entry->counters.usage *= STICKY_DECREASE_FACTOR;
else
entry->counters.usage *= USAGE_DECREASE_FACTOR;
/* In the mean length computation, ignore dropped texts. */
if (entry->query_len >= 0)
{
tottextlen += entry->query_len + 1;
nvalidtexts++;
}
}
/* Sort into increasing order by usage */
qsort(entries, i, sizeof(pgssEntry *), entry_cmp);
/* Record the (approximate) median usage */
if (i > 0)
pgss->cur_median_usage = entries[i / 2]->counters.usage;
/* Record the mean query length */
if (nvalidtexts > 0)
pgss->mean_query_len = tottextlen / nvalidtexts;
else
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
/* Now zap an appropriate fraction of lowest-usage entries */
nvictims = Max(10, i * USAGE_DEALLOC_PERCENT / 100);
nvictims = Min(nvictims, i);
for (i = 0; i < nvictims; i++)
{
hash_search(pgss_hash, &entries[i]->key, HASH_REMOVE, NULL);
}
pfree(entries);
/* Increment the number of times entries are deallocated */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
s->stats.dealloc += 1;
SpinLockRelease(&s->mutex);
}
}
/*
* Given a query string (not necessarily null-terminated), allocate a new
* entry in the external query text file and store the string there.
*
* If successful, returns true, and stores the new entry's offset in the file
* into *query_offset. Also, if gc_count isn't NULL, *gc_count is set to the
* number of garbage collections that have occurred so far.
*
* On failure, returns false.
*
* At least a shared lock on pgss->lock must be held by the caller, so as
* to prevent a concurrent garbage collection. Share-lock-holding callers
* should pass a gc_count pointer to obtain the number of garbage collections,
* so that they can recheck the count after obtaining exclusive lock to
* detect whether a garbage collection occurred (and removed this entry).
*/
static bool
qtext_store(const char *query, int query_len,
Size *query_offset, int *gc_count)
{
Size off;
int fd;
/*
* We use a spinlock to protect extent/n_writers/gc_count, so that
* multiple processes may execute this function concurrently.
*/
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
off = s->extent;
s->extent += query_len + 1;
s->n_writers++;
if (gc_count)
*gc_count = s->gc_count;
SpinLockRelease(&s->mutex);
}
*query_offset = off;
/*
* Don't allow the file to grow larger than what qtext_load_file can
* (theoretically) handle. This has been seen to be reachable on 32-bit
* platforms.
*/
if (unlikely(query_len >= MaxAllocHugeSize - off))
{
errno = EFBIG; /* not quite right, but it'll do */
fd = -1;
goto error;
}
/* Now write the data into the successfully-reserved part of the file */
fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDWR | O_CREAT | PG_BINARY);
if (fd < 0)
goto error;
if (pg_pwrite(fd, query, query_len, off) != query_len)
goto error;
if (pg_pwrite(fd, "\0", 1, off + query_len) != 1)
goto error;
CloseTransientFile(fd);
/* Mark our write complete */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
s->n_writers--;
SpinLockRelease(&s->mutex);
}
return true;
error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
if (fd >= 0)
CloseTransientFile(fd);
/* Mark our write complete */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
s->n_writers--;
SpinLockRelease(&s->mutex);
}
return false;
}
/*
* Read the external query text file into a malloc'd buffer.
*
* Returns NULL (without throwing an error) if unable to read, eg
* file not there or insufficient memory.
*
* On success, the buffer size is also returned into *buffer_size.
*
* This can be called without any lock on pgss->lock, but in that case
* the caller is responsible for verifying that the result is sane.
*/
static char *
qtext_load_file(Size *buffer_size)
{
char *buf;
int fd;
struct stat stat;
Size nread;
fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDONLY | PG_BINARY);
if (fd < 0)
{
if (errno != ENOENT)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": %m",
PGSS_TEXT_FILE)));
return NULL;
}
/* Get file length */
if (fstat(fd, &stat))
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m",
PGSS_TEXT_FILE)));
CloseTransientFile(fd);
return NULL;
}
/* Allocate buffer; beware that off_t might be wider than size_t */
if (stat.st_size <= MaxAllocHugeSize)
buf = (char *) malloc(stat.st_size);
else
buf = NULL;
if (buf == NULL)
{
ereport(LOG,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Could not allocate enough memory to read file \"%s\".",
PGSS_TEXT_FILE)));
CloseTransientFile(fd);
return NULL;
}
/*
* OK, slurp in the file. Windows fails if we try to read more than
* INT_MAX bytes at once, and other platforms might not like that either,
* so read a very large file in 1GB segments.
*/
nread = 0;
while (nread < stat.st_size)
{
int toread = Min(1024 * 1024 * 1024, stat.st_size - nread);
/*
* If we get a short read and errno doesn't get set, the reason is
* probably that garbage collection truncated the file since we did
* the fstat(), so we don't log a complaint --- but we don't return
* the data, either, since it's most likely corrupt due to concurrent
* writes from garbage collection.
*/
errno = 0;
if (read(fd, buf + nread, toread) != toread)
{
if (errno)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": %m",
PGSS_TEXT_FILE)));
free(buf);
CloseTransientFile(fd);
return NULL;
}
nread += toread;
}
if (CloseTransientFile(fd) != 0)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not close file \"%s\": %m", PGSS_TEXT_FILE)));
*buffer_size = nread;
return buf;
}
/*
* Locate a query text in the file image previously read by qtext_load_file().
*
* We validate the given offset/length, and return NULL if bogus. Otherwise,
* the result points to a null-terminated string within the buffer.
*/
static char *
qtext_fetch(Size query_offset, int query_len,
char *buffer, Size buffer_size)
{
/* File read failed? */
if (buffer == NULL)
return NULL;
/* Bogus offset/length? */
if (query_len < 0 ||
query_offset + query_len >= buffer_size)
return NULL;
/* As a further sanity check, make sure there's a trailing null */
if (buffer[query_offset + query_len] != '\0')
return NULL;
/* Looks OK */
return buffer + query_offset;
}
/*
* Do we need to garbage-collect the external query text file?
*
* Caller should hold at least a shared lock on pgss->lock.
*/
static bool
need_gc_qtexts(void)
{
Size extent;
/* Read shared extent pointer */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
extent = s->extent;
SpinLockRelease(&s->mutex);
}
/*
* Don't proceed if file does not exceed 512 bytes per possible entry.
*
* Here and in the next test, 32-bit machines have overflow hazards if
* pgss_max and/or mean_query_len are large. Force the multiplications
* and comparisons to be done in uint64 arithmetic to forestall trouble.
*/
if ((uint64) extent < (uint64) 512 * pgss_max)
return false;
/*
* Don't proceed if file is less than about 50% bloat. Nothing can or
* should be done in the event of unusually large query texts accounting
* for file's large size. We go to the trouble of maintaining the mean
* query length in order to prevent garbage collection from thrashing
* uselessly.
*/
if ((uint64) extent < (uint64) pgss->mean_query_len * pgss_max * 2)
return false;
return true;
}
/*
* Garbage-collect orphaned query texts in external file.
*
* This won't be called often in the typical case, since it's likely that
* there won't be too much churn, and besides, a similar compaction process
* occurs when serializing to disk at shutdown or as part of resetting.
* Despite this, it seems prudent to plan for the edge case where the file
* becomes unreasonably large, with no other method of compaction likely to
* occur in the foreseeable future.
*
* The caller must hold an exclusive lock on pgss->lock.
*
* At the first sign of trouble we unlink the query text file to get a clean
* slate (although existing statistics are retained), rather than risk
* thrashing by allowing the same problem case to recur indefinitely.
*/
static void
gc_qtexts(void)
{
char *qbuffer;
Size qbuffer_size;
FILE *qfile = NULL;
HASH_SEQ_STATUS hash_seq;
pgssEntry *entry;
Size extent;
int nentries;
/*
* When called from pgss_store, some other session might have proceeded
* with garbage collection in the no-lock-held interim of lock strength
* escalation. Check once more that this is actually necessary.
*/
if (!need_gc_qtexts())
return;
/*
* Load the old texts file. If we fail (out of memory, for instance),
* invalidate query texts. Hopefully this is rare. It might seem better
* to leave things alone on an OOM failure, but the problem is that the
* file is only going to get bigger; hoping for a future non-OOM result is
* risky and can easily lead to complete denial of service.
*/
qbuffer = qtext_load_file(&qbuffer_size);
if (qbuffer == NULL)
goto gc_fail;
/*
* We overwrite the query texts file in place, so as to reduce the risk of
* an out-of-disk-space failure. Since the file is guaranteed not to get
* larger, this should always work on traditional filesystems; though we
* could still lose on copy-on-write filesystems.
*/
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
goto gc_fail;
}
extent = 0;
nentries = 0;
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
int query_len = entry->query_len;
char *qry = qtext_fetch(entry->query_offset,
query_len,
qbuffer,
qbuffer_size);
if (qry == NULL)
{
/* Trouble ... drop the text */
entry->query_offset = 0;
entry->query_len = -1;
/* entry will not be counted in mean query length computation */
continue;
}
if (fwrite(qry, 1, query_len + 1, qfile) != query_len + 1)
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
hash_seq_term(&hash_seq);
goto gc_fail;
}
entry->query_offset = extent;
extent += query_len + 1;
nentries++;
}
/*
* Truncate away any now-unused space. If this fails for some odd reason,
* we log it, but there's no need to fail.
*/
if (ftruncate(fileno(qfile), extent) != 0)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not truncate file \"%s\": %m",
PGSS_TEXT_FILE)));
if (FreeFile(qfile))
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
qfile = NULL;
goto gc_fail;
}
elog(DEBUG1, "pgss gc of queries file shrunk size from %zu to %zu",
pgss->extent, extent);
/* Reset the shared extent pointer */
pgss->extent = extent;
/*
* Also update the mean query length, to be sure that need_gc_qtexts()
* won't still think we have a problem.
*/
if (nentries > 0)
pgss->mean_query_len = extent / nentries;
else
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
free(qbuffer);
/*
* OK, count a garbage collection cycle. (Note: even though we have
* exclusive lock on pgss->lock, we must take pgss->mutex for this, since
* other processes may examine gc_count while holding only the mutex.
* Also, we have to advance the count *after* we've rewritten the file,
* else other processes might not realize they read a stale file.)
*/
record_gc_qtexts();
return;
gc_fail:
/* clean up resources */
if (qfile)
FreeFile(qfile);
if (qbuffer)
free(qbuffer);
/*
* Since the contents of the external file are now uncertain, mark all
* hashtable entries as having invalid texts.
*/
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
entry->query_offset = 0;
entry->query_len = -1;
}
/*
* Destroy the query text file and create a new, empty one
*/
(void) unlink(PGSS_TEXT_FILE);
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not recreate file \"%s\": %m",
PGSS_TEXT_FILE)));
else
FreeFile(qfile);
/* Reset the shared extent pointer */
pgss->extent = 0;
/* Reset mean_query_len to match the new state */
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
/*
* Bump the GC count even though we failed.
*
* This is needed to make concurrent readers of file without any lock on
* pgss->lock notice existence of new version of file. Once readers
* subsequently observe a change in GC count with pgss->lock held, that
* forces a safe reopen of file. Writers also require that we bump here,
* of course. (As required by locking protocol, readers and writers don't
* trust earlier file contents until gc_count is found unchanged after
* pgss->lock acquired in shared or exclusive mode respectively.)
*/
record_gc_qtexts();
}
/*
* Release entries corresponding to parameters passed.
*/
static void
entry_reset(Oid userid, Oid dbid, uint64 queryid)
{
HASH_SEQ_STATUS hash_seq;
pgssEntry *entry;
FILE *qfile;
long num_entries;
long num_remove = 0;
pgssHashKey key;
if (!pgss || !pgss_hash)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));
LWLockAcquire(pgss->lock, LW_EXCLUSIVE);
num_entries = hash_get_num_entries(pgss_hash);
if (userid != 0 && dbid != 0 && queryid != UINT64CONST(0))
{
/* If all the parameters are available, use the fast path. */
memset(&key, 0, sizeof(pgssHashKey));
key.userid = userid;
key.dbid = dbid;
key.queryid = queryid;
/* Remove the key if it exists, starting with the top-level entry */
key.toplevel = false;
entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_REMOVE, NULL);
if (entry) /* found */
num_remove++;
/* Also remove entries for top level statements */
key.toplevel = true;
/* Remove the key if exists */
entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_REMOVE, NULL);
if (entry) /* found */
num_remove++;
}
else if (userid != 0 || dbid != 0 || queryid != UINT64CONST(0))
{
/* Remove entries corresponding to valid parameters. */
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
if ((!userid || entry->key.userid == userid) &&
(!dbid || entry->key.dbid == dbid) &&
(!queryid || entry->key.queryid == queryid))
{
hash_search(pgss_hash, &entry->key, HASH_REMOVE, NULL);
num_remove++;
}
}
}
else
{
/* Remove all entries. */
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
hash_search(pgss_hash, &entry->key, HASH_REMOVE, NULL);
num_remove++;
}
}
/* All entries are removed? */
if (num_entries != num_remove)
goto release_lock;
/*
* Reset global statistics for pg_stat_statements since all entries are
* removed.
*/
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
TimestampTz stats_reset = GetCurrentTimestamp();
SpinLockAcquire(&s->mutex);
s->stats.dealloc = 0;
s->stats.stats_reset = stats_reset;
SpinLockRelease(&s->mutex);
}
/*
* Write new empty query file, perhaps even creating a new one to recover
* if the file was missing.
*/
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not create file \"%s\": %m",
PGSS_TEXT_FILE)));
goto done;
}
/* If ftruncate fails, log it, but it's not a fatal problem */
if (ftruncate(fileno(qfile), 0) != 0)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not truncate file \"%s\": %m",
PGSS_TEXT_FILE)));
FreeFile(qfile);
done:
pgss->extent = 0;
/* This counts as a query text garbage collection for our purposes */
record_gc_qtexts();
release_lock:
LWLockRelease(pgss->lock);
}
/*
* Generate a normalized version of the query string that will be used to
* represent all similar queries.
*
* Note that the normalized representation may well vary depending on
* just which "equivalent" query is used to create the hashtable entry.
* We assume this is OK.
*
* If query_loc > 0, then "query" has been advanced by that much compared to
* the original string start, so we need to translate the provided locations
* to compensate. (This lets us avoid re-scanning statements before the one
* of interest, so it's worth doing.)
*
* *query_len_p contains the input string length, and is updated with
* the result string length on exit. The resulting string might be longer
* or shorter depending on what happens with replacement of constants.
*
* Returns a palloc'd string.
*/
static char *
generate_normalized_query(JumbleState *jstate, const char *query,
int query_loc, int *query_len_p)
{
char *norm_query;
int query_len = *query_len_p;
int i,
norm_query_buflen, /* Space allowed for norm_query */
len_to_wrt, /* Length (in bytes) to write */
quer_loc = 0, /* Source query byte location */
n_quer_loc = 0, /* Normalized query byte location */
last_off = 0, /* Offset from start for previous tok */
last_tok_len = 0; /* Length (in bytes) of that tok */
/*
* Get constants' lengths (core system only gives us locations). Note
* this also ensures the items are sorted by location.
*/
fill_in_constant_lengths(jstate, query, query_loc);
/*
* Allow for $n symbols to be longer than the constants they replace.
* Constants must take at least one byte in text form, while a $n symbol
* certainly isn't more than 11 bytes, even if n reaches INT_MAX. We
* could refine that limit based on the max value of n for the current
* query, but it hardly seems worth any extra effort to do so.
*/
norm_query_buflen = query_len + jstate->clocations_count * 10;
/* Allocate result buffer */
norm_query = palloc(norm_query_buflen + 1);
for (i = 0; i < jstate->clocations_count; i++)
{
int off, /* Offset from start for cur tok */
tok_len; /* Length (in bytes) of that tok */
off = jstate->clocations[i].location;
/* Adjust recorded location if we're dealing with partial string */
off -= query_loc;
tok_len = jstate->clocations[i].length;
if (tok_len < 0)
continue; /* ignore any duplicates */
/* Copy next chunk (what precedes the next constant) */
len_to_wrt = off - last_off;
len_to_wrt -= last_tok_len;
Assert(len_to_wrt >= 0);
memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
n_quer_loc += len_to_wrt;
/* And insert a param symbol in place of the constant token */
n_quer_loc += sprintf(norm_query + n_quer_loc, "$%d",
i + 1 + jstate->highest_extern_param_id);
quer_loc = off + tok_len;
last_off = off;
last_tok_len = tok_len;
}
/*
* We've copied up until the last ignorable constant. Copy over the
* remaining bytes of the original query string.
*/
len_to_wrt = query_len - quer_loc;
Assert(len_to_wrt >= 0);
memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
n_quer_loc += len_to_wrt;
Assert(n_quer_loc <= norm_query_buflen);
norm_query[n_quer_loc] = '\0';
*query_len_p = n_quer_loc;
return norm_query;
}
/*
* Given a valid SQL string and an array of constant-location records,
* fill in the textual lengths of those constants.
*
* The constants may use any allowed constant syntax, such as float literals,
* bit-strings, single-quoted strings and dollar-quoted strings. This is
* accomplished by using the public API for the core scanner.
*
* It is the caller's job to ensure that the string is a valid SQL statement
* with constants at the indicated locations. Since in practice the string
* has already been parsed, and the locations that the caller provides will
* have originated from within the authoritative parser, this should not be
* a problem.
*
* Duplicate constant pointers are possible, and will have their lengths
* marked as '-1', so that they are later ignored. (Actually, we assume the
* lengths were initialized as -1 to start with, and don't change them here.)
*
* If query_loc > 0, then "query" has been advanced by that much compared to
* the original string start, so we need to translate the provided locations
* to compensate. (This lets us avoid re-scanning statements before the one
* of interest, so it's worth doing.)
*
* N.B. There is an assumption that a '-' character at a Const location begins
* a negative numeric constant. This precludes there ever being another
* reason for a constant to start with a '-'.
*/
static void
fill_in_constant_lengths(JumbleState *jstate, const char *query,
int query_loc)
{
LocationLen *locs;
core_yyscan_t yyscanner;
core_yy_extra_type yyextra;
core_YYSTYPE yylval;
YYLTYPE yylloc;
int last_loc = -1;
int i;
/*
* Sort the records by location so that we can process them in order while
* scanning the query text.
*/
if (jstate->clocations_count > 1)
qsort(jstate->clocations, jstate->clocations_count,
sizeof(LocationLen), comp_location);
locs = jstate->clocations;
/* initialize the flex scanner --- should match raw_parser() */
yyscanner = scanner_init(query,
&yyextra,
&ScanKeywords,
ScanKeywordTokens);
/* we don't want to re-emit any escape string warnings */
yyextra.escape_string_warning = false;
/* Search for each constant, in sequence */
for (i = 0; i < jstate->clocations_count; i++)
{
int loc = locs[i].location;
int tok;
/* Adjust recorded location if we're dealing with partial string */
loc -= query_loc;
Assert(loc >= 0);
if (loc <= last_loc)
continue; /* Duplicate constant, ignore */
/* Lex tokens until we find the desired constant */
for (;;)
{
tok = core_yylex(&yylval, &yylloc, yyscanner);
/* We should not hit end-of-string, but if we do, behave sanely */
if (tok == 0)
break; /* out of inner for-loop */
/*
* We should find the token position exactly, but if we somehow
* run past it, work with that.
*/
if (yylloc >= loc)
{
if (query[loc] == '-')
{
/*
* It's a negative value - this is the one and only case
* where we replace more than a single token.
*
* Do not compensate for the core system's special-case
* adjustment of location to that of the leading '-'
* operator in the event of a negative constant. It is
* also useful for our purposes to start from the minus
* symbol. In this way, queries like "select * from foo
* where bar = 1" and "select * from foo where bar = -2"
* will have identical normalized query strings.
*/
tok = core_yylex(&yylval, &yylloc, yyscanner);
if (tok == 0)
break; /* out of inner for-loop */
}
/*
* We now rely on the assumption that flex has placed a zero
* byte after the text of the current token in scanbuf.
*/
locs[i].length = strlen(yyextra.scanbuf + loc);
break; /* out of inner for-loop */
}
}
/* If we hit end-of-string, give up, leaving remaining lengths -1 */
if (tok == 0)
break;
last_loc = loc;
}
scanner_finish(yyscanner);
}
/*
* comp_location: comparator for qsorting LocationLen structs by location
*/
static int
comp_location(const void *a, const void *b)
{
int l = ((const LocationLen *) a)->location;
int r = ((const LocationLen *) b)->location;
if (l < r)
return -1;
else if (l > r)
return +1;
else
return 0;
}
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