From 74c67a38126bac2b991753ab214f06407ef81ffc Mon Sep 17 00:00:00 2001
From: Yuri Astrakhan <yuriastrakhan@gmail.com>
Date: Sat, 27 Jan 2024 21:48:54 -0500
Subject: [PATCH] Use ORDERBY in calc_agg_tiles_hash - SQLite v3.44 (#1156)

Require SQLite v3.44+ ORDER BY clause inside aggregate function instead
of the windowing one - might solve out of memory issues reported by
users - see #1154
---
 Cargo.toml                |  2 +-
 mbtiles/src/validation.rs | 14 +++++---------
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 37a31fca..deb53b7c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -72,7 +72,7 @@ serde_with = "3"
 serde_yaml = "0.9"
 size_format = "1.0.2"
 spreet = { version = "0.11", default-features = false }
-sqlite-hashes = { version = "0.6", default-features = false, features = ["md5", "window", "hex"] }
+sqlite-hashes = { version = "0.6", default-features = false, features = ["md5", "window", "hex"] }  # window forces libsqlite3-sys to bundle sqlite3. We require v3.44.0 or newer.
 sqlx = { version = "0.7", features = ["sqlite", "runtime-tokio"] }
 subst = { version = "0.3", features = ["yaml"] }
 thiserror = "1"
diff --git a/mbtiles/src/validation.rs b/mbtiles/src/validation.rs
index 9680a980..50509a81 100644
--- a/mbtiles/src/validation.rs
+++ b/mbtiles/src/validation.rs
@@ -470,22 +470,18 @@ where
         // `md5` functions will fail if the value is not text/blob/null
         //
         // Note that ORDER BY controls the output ordering, which is important for the hash value,
-        // and having it at the top level would not order values properly.
+        // and we must use ORDER BY as a parameter to the aggregate function itself (available since SQLite 3.44.0)
         // See https://sqlite.org/forum/forumpost/228bb96e12a746ce
         "
 SELECT coalesce(
-    (SELECT md5_concat_hex(
+           md5_concat_hex(
                cast(zoom_level AS text),
                cast(tile_column AS text),
                cast(tile_row AS text),
                tile_data
-           )
-           OVER (ORDER BY zoom_level, tile_column, tile_row ROWS
-                 BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
-     FROM tiles
-     LIMIT 1),
-    md5_hex('')
-);
+               ORDER BY zoom_level, tile_column, tile_row),
+           md5_hex(''))
+FROM tiles;
 ",
     );
     Ok(query.fetch_one(conn).await?.get::<String, _>(0))