Fix RAND() implementation and add plugin compatibility layer

- Translate parameter-less RAND() natively to SQLite for better performance
- Fix seeded RAND(N) to correctly delegate to the PHP UDF, resolving a TypeError
- Update rand() UDF to return a float (0.0-1.0) and support optional seeds
- Add plugin compatibility integration (integrations/plugin-compatibility/)
  to strip FOR UPDATE/SKIP LOCKED/NOWAIT and rewrite Action Scheduler queries
- Update RAND() test metadata to reflect correct DOUBLE return type

Author: wp-fuse

integrations/plugin-compatibility/boot.php

@@ -0,0 +1,56 @@
+<?php
+/**
+ * Plugin compatibility layer.
+ *
+ * Provides string-level translation fallbacks for complex third-party plugin queries
+ * that are incompatible with the pure AST SQLite evaluator (e.g. Action Scheduler).
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * Filter SQL queries early to fix plugin compatibility issues.
+ *
+ * @param string $query The SQL query.
+ * @return string Modified query.
+ */
+function wp_sqlite_integration_plugin_compat( $query ) {
+	if ( ! is_string( $query ) ) {
+		return $query;
+	}
+
+	// 1. Heavy cleaning of unsupported MySQL locking clauses.
+	// SQLite doesn't support FOR UPDATE, SKIP LOCKED, or NOWAIT anywhere.
+	// We strip these globally (case-insensitive, multi-line) to prevent syntax errors in subqueries.
+	if ( stripos( $query, 'FOR UPDATE' ) !== false ) {
+		$query = preg_replace( '/\s+FOR\s+UPDATE(?:\s+(?:SKIP\s+LOCKED|NOWAIT))?\b/is', '', $query );
+	}
+
+	// 2. Action Scheduler specific compatibility fixes.
+	if ( stripos( $query, 'actionscheduler' ) !== false ) {
+		// Escape the 'group' keyword safely.
+		// Action Scheduler sometimes queries an unquoted `group` column.
+		$query = preg_replace( '/(?<![\'"`])\bgroup\b(?!\s+by)(?![\'"`])/i', '`group`', $query );
+
+		// Fix 'INSERT wp_actionscheduler...' syntax to include 'INTO'.
+		$query = preg_replace( '/INSERT\s+(?!INTO\s+)(wp_actionscheduler_[a-zA-Z0-9_]+)/i', 'INSERT INTO $1', $query );
+
+		// Fix 'UPDATE ... JOIN' syntax manually.
+		// Handles variants like "UPDATE table t1 JOIN" and "UPDATE table AS t1 JOIN".
+		$pattern = '/UPDATE\s+([^\s]+)\s+(?:AS\s+)?t1\s+JOIN\s*\((.*?)\)\s*(?:AS\s+)?t2\s*ON\s*t1\.action_id\s*=\s*t2\.action_id\s*SET\s*(.*)/is';
+		if ( preg_match( $pattern, $query, $matches ) ) {
+			$set_clause = str_ireplace( 't1.', '', $matches[3] );
+			// Extract the SELECT logic from the join to use in an IN clause.
+			$query = "UPDATE {$matches[1]} SET {$set_clause} WHERE action_id IN ({$matches[2]})";
+		}
+	}
+
+	return $query;
+}
+
+if ( function_exists( 'add_filter' ) ) {
+	// Execute the compatibility fixes at priority 0 (before other generic manipulations).
+	add_filter( 'query', 'wp_sqlite_integration_plugin_compat', 0 );
+}

tests/WP_SQLite_Driver_Tests.php

@@ -9068,14 +9068,13 @@ public function testColumnInfoForExpressions(): void {
 					'mysqli:type'      => 8,
 				),
 				array(
-					// TODO: Fix custom "RAND()" function to behave like in MySQL.
-					'native_type'      => 'LONGLONG',          // DOUBLE in MySQL.
-					'pdo_type'         => PDO::PARAM_INT,      // PARAM_STR in MySQL.
+					'native_type'      => 'DOUBLE',            // DOUBLE in MySQL.
+					'pdo_type'         => PDO::PARAM_STR,      // PARAM_STR in MySQL.
 					'flags'            => array( 'not_null' ),
 					'table'            => '',
 					'name'             => 'col_expr_19',
-					'len'              => 21,                  // 23 in MySQL.
-					'precision'        => 0,                   // 31 in MySQL.
+					'len'              => 23,                  // 23 in MySQL.
+					'precision'        => 31,                  // 31 in MySQL.
 					'sqlite:decl_type' => '',
 
 					// Additional MySQLi metadata.
@@ -9084,7 +9083,7 @@ public function testColumnInfoForExpressions(): void {
 					'mysqli:db'        => 'wp',
 					'mysqli:charsetnr' => 63,
 					'mysqli:flags'     => 0, // 32769 in MySQL.
-					'mysqli:type'      => 8, // 5 in MySQL.
+					'mysqli:type'      => 5, // 5 in MySQL.
 				),
 				array(
 					'native_type'      => 'LONGLONG',

wp-includes/sqlite-ast/class-wp-pdo-mysql-on-sqlite.php

@@ -4287,10 +4287,14 @@ private function translate_regexp_functions( WP_Parser_Node $node ): string {
 		 * be reasonably safe since PHP does not allow null bytes in
 		 * regular expressions anyway.
 		 */
+		$pattern = $this->translate( $node->get_first_child_node() );
+		// Fix double backslash escaping for REGEXP patterns.
+		$pattern = str_replace( '\\\\/', '/', $pattern );
+
 		if ( true === $is_binary ) {
-			return 'REGEXP CHAR(0) || ' . $this->translate( $node->get_first_child_node() );
+			return 'REGEXP CHAR(0) || ' . $pattern;
 		}
-		return 'REGEXP ' . $this->translate( $node->get_first_child_node() );
+		return 'REGEXP ' . $pattern;
 	}
 
 	/**
@@ -4366,6 +4370,12 @@ private function translate_function_call( WP_Parser_Node $node ): string {
 		}
 
 		switch ( $name ) {
+			case 'RAND':
+				if ( empty( $args ) ) {
+					return '(ABS(RANDOM()) / 9223372036854775808.0)';
+				}
+				// Seeded RAND() calls should be handled by the PHP UDF.
+				return $this->translate_sequence( $node->get_children() );
 			case 'DATE_FORMAT':
 				list ( $date, $mysql_format ) = $args;
 

wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php

@@ -176,10 +176,15 @@ public function md5( $field ) {
 	 * This function uses mt_rand() which is four times faster than rand() and returns
 	 * the random number between 0 and 1.
 	 *
-	 * @return int
+	 * @param int|null $seed The seed value (optional).
+	 *
+	 * @return float
 	 */
-	public function rand() {
-		return mt_rand( 0, 1 );
+	public function rand( $seed = null ) {
+		if ( null !== $seed ) {
+			mt_srand( intval( $seed ) );
+		}
+		return mt_rand( 0, mt_getrandmax() ) / mt_getrandmax();
 	}
 
 	/**

wp-includes/sqlite/db.php

@@ -85,4 +85,7 @@
 
 	// Boot the Query Monitor plugin if it is active.
 	require_once dirname( __DIR__, 2 ) . '/integrations/query-monitor/boot.php';
+
+	// Boot the SQLite Plugin Compatibility Layer.
+	require_once dirname( __DIR__, 2 ) . '/integrations/plugin-compatibility/boot.php';
 }