Probe correlated subquery against REAL sqlite_sequence too

The earlier probe used a fake `sqlseq` regular table. The real
driver uses Turso's `sqlite_sequence` (a special table populated
by INTEGER PRIMARY KEY AUTOINCREMENT). Turso has known special
handling for sqlite_sequence (writes are forbidden, reads may
hit a different code path).

Test the same 4 query shapes against both fake `sqlseq` and real
`sqlite_sequence` to see whether the special table is the trigger.
Also dump sqlite_sequence to verify it has the expected values.

Author: JanJakes

.github/workflows/phpunit-tests-turso.yml

@@ -1094,14 +1094,22 @@ jobs:
           // Reproduce testInformationSchemaTablesFilterByAutoIncrement's exact
           // shape — info_schema-style tables and the *exact* translate_table_ref
           // correlated subquery (LEFT JOIN inside subquery + COALESCE).
+          // Also use Turso's REAL `sqlite_sequence` (a special table) by
+          // creating tables with INTEGER PRIMARY KEY AUTOINCREMENT, which
+          // is what the driver sets up for AUTO_INCREMENT columns.
           $pdo = new PDO('sqlite::memory:');
           $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
           // Mirror the driver's information schema layout and seed it.
           $pdo->exec("CREATE TABLE _ist (table_schema TEXT, table_name TEXT, engine TEXT)");
           $pdo->exec("CREATE TABLE _isc (table_schema TEXT, table_name TEXT, column_name TEXT, extra TEXT)");
           $pdo->exec("INSERT INTO _ist VALUES ('main','low','InnoDB'), ('main','high','InnoDB'), ('main','plain','InnoDB')");
           $pdo->exec("INSERT INTO _isc VALUES ('main','low','id','auto_increment'), ('main','high','id','auto_increment'), ('main','plain','id','')");
-          // sqlite_sequence is auto-managed; emulate with a regular table called sqlseq.
+          // Real sqlite_sequence: create AUTOINCREMENT tables and insert.
+          $pdo->exec("CREATE TABLE low (id INTEGER PRIMARY KEY AUTOINCREMENT, n TEXT)");
+          $pdo->exec("CREATE TABLE high (id INTEGER PRIMARY KEY AUTOINCREMENT, n TEXT)");
+          $pdo->exec("INSERT INTO low (n) VALUES ('a')");
+          $pdo->exec("INSERT INTO high (n) VALUES ('a'),('b'),('c'),('d'),('e')");
+          // (Also keep the fake table for comparison — used in the cases below.)
           $pdo->exec("CREATE TABLE sqlseq (name TEXT, seq INT)");
           $pdo->exec("INSERT INTO sqlseq VALUES ('low',1), ('high',5)");
 
@@ -1115,23 +1123,35 @@ jobs:
 
           $derived = "(SELECT table_name AS NAME, $corr AS AI FROM _ist AS t)";
 
+          // Variants using REAL sqlite_sequence (special table populated by AUTOINCREMENT)
+          $real_corr = "(SELECT COALESCE(s.seq + 1, 1)
+                    FROM _isc AS c
+                    LEFT JOIN sqlite_sequence AS s ON s.name = c.table_name
+                    WHERE c.extra = 'auto_increment'
+                    AND c.table_schema = t.table_schema
+                    AND c.table_name = t.table_name)";
+          $real_derived = "(SELECT table_name AS NAME, $real_corr AS AI FROM _ist AS t)";
+
           $cases = [
-              'inline correlated subq value' =>
+              'fake-seq inline correlated subq value' =>
                   "SELECT table_name, $corr AS AI FROM _ist AS t",
-              'derived-table + WHERE AI > 3 (the bug)' =>
+              'fake-seq derived-table + WHERE AI > 3 (the bug)' =>
                   "SELECT NAME FROM $derived WHERE AI > 3",
-              'derived-table + WHERE AI IS NULL' =>
+              'fake-seq derived-table + WHERE AI IS NULL' =>
                   "SELECT NAME FROM $derived WHERE AI IS NULL",
-              'derived-table + plain SELECT' =>
+              'fake-seq derived-table + plain SELECT' =>
                   "SELECT NAME, AI FROM $derived",
-              'derived-table + WHERE on AI with length(t.name) > 0 forced' =>
-                  ("SELECT NAME FROM (SELECT table_name AS NAME, "
-                   . "(SELECT COALESCE(s.seq + 1, 1) FROM _isc AS c "
-                   . "LEFT JOIN sqlseq AS s ON s.name = c.table_name "
-                   . "WHERE c.extra='auto_increment' "
-                   . "AND c.table_schema = t.table_schema "
-                   . "AND c.table_name = t.table_name "
-                   . "AND length(t.table_name) > 0) AS AI FROM _ist AS t) WHERE AI > 3"),
+              'real-seq inline correlated subq value' =>
+                  "SELECT table_name, $real_corr AS AI FROM _ist AS t",
+              'real-seq derived-table + WHERE AI > 3 (the bug)' =>
+                  "SELECT NAME FROM $real_derived WHERE AI > 3",
+              'real-seq derived-table + WHERE AI IS NULL' =>
+                  "SELECT NAME FROM $real_derived WHERE AI IS NULL",
+              'real-seq derived-table + plain SELECT' =>
+                  "SELECT NAME, AI FROM $real_derived",
+              // Just dump real sqlite_sequence to confirm it has the right values
+              'real sqlite_sequence dump' =>
+                  "SELECT name, seq FROM sqlite_sequence ORDER BY name",
           ];
           foreach ($cases as $label => $sql) {
               try {