Implement SHOW DATABASES statement

Author: JanJakes

tests/WP_SQLite_Driver_Metadata_Tests.php

@@ -371,6 +371,64 @@ public function testRepairTable() {
 		);
 	}
 
+	public function testShowDatabases(): void {
+		// Simple.
+		$this->assertQuery( 'SHOW DATABASES' );
+		$actual = $this->engine->get_query_results();
+		$this->assertEquals(
+			array(
+				(object) array( 'Database' => 'information_schema' ),
+				(object) array( 'Database' => 'wp' ),
+			),
+			$actual
+		);
+
+		// With LIKE clause.
+		$this->assertQuery( 'SHOW DATABASES LIKE "w%"' );
+		$actual = $this->engine->get_query_results();
+		$this->assertEquals(
+			array( (object) array( 'Database' => 'wp' ) ),
+			$actual
+		);
+
+		// With WHERE clause.
+		$this->assertQuery( 'SHOW DATABASES WHERE `Database` = "wp"' );
+		$actual = $this->engine->get_query_results();
+		$this->assertEquals(
+			array( (object) array( 'Database' => 'wp' ) ),
+			$actual
+		);
+	}
+
+	public function testShowTableSchemas(): void {
+		$this->assertQuery( 'SHOW SCHEMAS' );
+
+		$actual = $this->engine->get_query_results();
+		$this->assertEquals(
+			array(
+				(object) array( 'Database' => 'information_schema' ),
+				(object) array( 'Database' => 'wp' ),
+			),
+			$actual
+		);
+
+		// With LIKE clause.
+		$this->assertQuery( 'SHOW DATABASES LIKE "inf%"' );
+		$actual = $this->engine->get_query_results();
+		$this->assertEquals(
+			array( (object) array( 'Database' => 'information_schema' ) ),
+			$actual
+		);
+
+		// With WHERE clause.
+		$this->assertQuery( 'SHOW DATABASES WHERE `Database` = "information_schema"' );
+		$actual = $this->engine->get_query_results();
+		$this->assertEquals(
+			array( (object) array( 'Database' => 'information_schema' ) ),
+			$actual
+		);
+	}
+
 	public function testShowTableStatus() {
 		$this->assertQuery( 'CREATE TABLE t ( comment_author TEXT, comment_content TEXT )' );
 

wp-includes/sqlite-ast/class-wp-sqlite-driver.php

@@ -1594,6 +1594,9 @@ private function execute_show_statement( WP_Parser_Node $node ): void {
 		$keyword2 = $tokens[2] ?? null;
 
 		switch ( $keyword1->id ) {
+			case WP_MySQL_Lexer::DATABASES_SYMBOL:
+				$this->execute_show_databases_statement( $node );
+				break;
 			case WP_MySQL_Lexer::COLUMNS_SYMBOL:
 			case WP_MySQL_Lexer::FIELDS_SYMBOL:
 				$this->execute_show_columns_statement( $node );
@@ -1658,6 +1661,31 @@ private function execute_show_statement( WP_Parser_Node $node ): void {
 		}
 	}
 
+	/**
+	 * Translate and execute a MySQL SHOW DATABASES statement in SQLite.
+	 *
+	 * @param  WP_Parser_Node $node The "showStatement" AST node.
+	 */
+	private function execute_show_databases_statement( WP_Parser_Node $node ): void {
+		$schemata_table = $this->information_schema_builder->get_table_name( false, 'schemata' );
+
+		// LIKE and WHERE clauses.
+		$like_or_where = $node->get_first_child_node( 'likeOrWhere' );
+		if ( null !== $like_or_where ) {
+			$condition = $this->translate_show_like_or_where_condition( $like_or_where, 'schema_name' );
+		}
+
+		$databases = $this->execute_sqlite_query(
+			sprintf(
+				'SELECT SCHEMA_NAME AS Database FROM %s%s ORDER BY SCHEMA_NAME',
+				$this->quote_sqlite_identifier( $schemata_table ),
+				isset( $condition ) ? ( ' WHERE TRUE ' . $condition ) : ''
+			)
+		)->fetchAll( PDO::FETCH_OBJ );
+
+		$this->set_results_from_fetched_data( $databases );
+	}
+
 	/**
 	 * Translate and execute a MySQL SHOW INDEX statement in SQLite.
 	 *