Fix performance issue on PG Tile Store (#909, #912)

The query optimizer of Postgres 15 is not able to push conditions down when using sub-queries. Therefore, we now append the spatial conditions to the sub-query. The unit tests have been adapted accordingly. A more robust solution involving a query parser will be devised (#913) in the future to account for more complex queries (GROUP BY, HAVING, etc.).

---------

Co-authored-by: AlexGacon <alexandre.gacon@gmail.com>

Author: bchapuis

baremaps-core/src/main/java/org/apache/baremaps/tilestore/postgres/PostgresTileStore.java

@@ -21,7 +21,7 @@
 import java.io.ByteArrayOutputStream;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
-import java.sql.*;
+import java.sql.ResultSet;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.zip.GZIPOutputStream;
@@ -64,7 +64,7 @@ public PostgresTileStore(DataSource datasource, Tileset tileset) {
 
   /**
    * A record that holds the sql of a prepared statement and the number of parameters.
-   * 
+   *
    * @param sql
    * @param parameters
    */
@@ -163,10 +163,26 @@ protected static Query prepareQuery(Tileset tileset, int zoom) {
               .replace(";", "")
               .replace("?", "??")
               .replace("$zoom", String.valueOf(zoom));
+
+          // Append a new condition or a where clause
+          if (querySql.toLowerCase().contains("where")) {
+            querySql += " AND ";
+          } else {
+            querySql += " WHERE ";
+          }
+
+          // Append the condition to the query sql
+          querySql +=
+              "geom IS NOT NULL AND geom && ST_TileEnvelope(?, ?, ?, margin => (64.0/4096))";
+
           var querySqlWithParams = String.format(
-              "SELECT ST_AsMVTGeom(t.geom, ST_TileEnvelope(?, ?, ?)) AS geom, t.tags - 'id' AS tags, t.id AS id "
-                  + "FROM (%s) AS t WHERE t.geom IS NOT NULL "
-                  + "AND t.geom && ST_TileEnvelope(?, ?, ?, margin => (64.0/4096))",
+              """
+                  SELECT
+                    tile.id AS id,
+                    tile.tags - 'id' AS tags,
+                    ST_AsMVTGeom(tile.geom, ST_TileEnvelope(?, ?, ?)) AS geom
+                  FROM (%s) as tile
+                  """,
               querySql);
           layerSql.append(querySqlWithParams);
 
@@ -201,7 +217,7 @@ protected static Query prepareQuery(Tileset tileset, int zoom) {
     tileSql.append(tileQueryTail);
 
     // Format the sql query
-    var sql = tileSql.toString().replace("\n", " ");
+    var sql = tileSql.toString().replaceAll("\\s+", " ");
 
     return new Query(sql, paramCount);
   }

baremaps-core/src/test/java/org/apache/baremaps/tilestore/postgres/PostgresTileStoreTest.java

@@ -40,7 +40,7 @@ void prepareQuery() {
             List.of(new TilesetQuery(0, 20, "SELECT id, tags, geom FROM table")))));
     var query = PostgresTileStore.prepareQuery(tileset, 10);
     assertEquals(
-        "SELECT (SELECT ST_AsMVT(mvtGeom.*, 'a') FROM (SELECT ST_AsMVTGeom(t.geom, ST_TileEnvelope(?, ?, ?)) AS geom, t.tags - 'id' AS tags, t.id AS id FROM (SELECT id, tags, geom FROM table) AS t WHERE t.geom IS NOT NULL AND t.geom && ST_TileEnvelope(?, ?, ?, margin => (64.0/4096))) AS mvtGeom) || (SELECT ST_AsMVT(mvtGeom.*, 'b') FROM (SELECT ST_AsMVTGeom(t.geom, ST_TileEnvelope(?, ?, ?)) AS geom, t.tags - 'id' AS tags, t.id AS id FROM (SELECT id, tags, geom FROM table) AS t WHERE t.geom IS NOT NULL AND t.geom && ST_TileEnvelope(?, ?, ?, margin => (64.0/4096))) AS mvtGeom) AS mvtTile",
+        "SELECT (SELECT ST_AsMVT(mvtGeom.*, 'a') FROM (SELECT tile.id AS id, tile.tags - 'id' AS tags, ST_AsMVTGeom(tile.geom, ST_TileEnvelope(?, ?, ?)) AS geom FROM (SELECT id, tags, geom FROM table WHERE geom IS NOT NULL AND geom && ST_TileEnvelope(?, ?, ?, margin => (64.0/4096))) as tile ) AS mvtGeom) || (SELECT ST_AsMVT(mvtGeom.*, 'b') FROM (SELECT tile.id AS id, tile.tags - 'id' AS tags, ST_AsMVTGeom(tile.geom, ST_TileEnvelope(?, ?, ?)) AS geom FROM (SELECT id, tags, geom FROM table WHERE geom IS NOT NULL AND geom && ST_TileEnvelope(?, ?, ?, margin => (64.0/4096))) as tile ) AS mvtGeom) AS mvtTile",
         query.sql());
   }
 }