From 08d072806c37ffa750770ec7a811aab7b763ff16 Mon Sep 17 00:00:00 2001
From: konradh <49533343+konradh@users.noreply.github.com>
Date: Sun, 5 Nov 2023 16:03:18 +0100
Subject: [PATCH] fix(sqlite): improve floating-point precision

This adds support for values of type double when binding values to a
query. Prior to this, doubles would be converted to a string and only
be stored with 6 digits of precision in the database.

Additionally, floats stored in the database were converted to strings
when retrieved and therefore be reduced to 6 digits of precision, too.
---
 sqlite.d | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/sqlite.d b/sqlite.d
index 44c6ba4..191ee3f 100644
--- a/sqlite.d
+++ b/sqlite.d
@@ -237,6 +237,9 @@ class SqliteResult :  ResultSet {
 		foreach(c; rows[position]) {
 			if(auto t = c.peek!(immutable(byte)[]))
 				r.row ~= DatabaseDatum(cast(string) *t);
+			else if (auto d = c.peek!double)
+				// 17 significant decimal digits are enough to not lose precision (IEEE 754 section 5.12.2)
+				r.row ~= DatabaseDatum(format!"%.17s"(*d));
 			else
 				r.row ~= DatabaseDatum(c.coerce!(string));
 		}
@@ -508,6 +511,7 @@ template extract(A, T, R...){
 		void bind (const char[] name, const char[] value){ bind(bindNameLookUp(name), value); }
 		void bind (const char[] name, int value){ bind(bindNameLookUp(name), value); }
 		void bind (const char[] name, float value){ bind(bindNameLookUp(name), value); }
+		void bind (const char[] name, double value){ bind(bindNameLookUp(name), value); }
 		void bind (const char[] name, const byte[] value){ bind(bindNameLookUp(name), value); }
 		void bind (const char[] name, const ubyte[] value){ bind(bindNameLookUp(name), value); }
 
@@ -525,6 +529,11 @@ template extract(A, T, R...){
 			throw new DatabaseException("bind " ~ db.error());
 	}
 
+	void bind(int col, double value){
+		if(sqlite3_bind_double(s, col, value) != SQLITE_OK)
+			throw new DatabaseException("bind " ~ db.error());
+	}
+
 	void bind(int col, int value){
 		if(sqlite3_bind_int(s, col, value) != SQLITE_OK)
 			throw new DatabaseException("bind " ~ db.error());
@@ -572,6 +581,8 @@ template extract(A, T, R...){
 			bind(col, v.get!string);
 		else if(v.peek!float)
 			bind(col, v.get!float);
+		else if(v.peek!double)
+			bind(col, v.get!double);
 		else if(v.peek!(byte[]))
 			bind(col, v.get!(byte[]));
 		else if(v.peek!(ubyte[]))