ext/pdo_pgsql: Retrieve the memory usage of the query result resource (php#14260)

`getAttribute()` can now retrieve the memory usage of query results.
`PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE` was added for this feature.

closes php#14260

Author: KentarouTakeda

NEWS

@@ -175,6 +175,7 @@ PHP                                                                        NEWS
     PDO constructor arguments. (SakiTakamachi)
   . Fixed native float support with pdo_pgsql query results. (Yurunsoft)
   . Added class PdoPgsql. (danack, kocsismate)
+  . Retrieve the memory usage of the query result resource. (KentarouTakeda)
 
 - PDO_SQLITE:
   . Added class PdoSqlite. (danack, kocsismate)

UPGRADING

@@ -421,6 +421,10 @@ PHP 8.4 UPGRADE NOTES
 - PDO_MYSQL:
   . getAttribute, enabled to get the value of ATTR_FETCH_TABLE_NAMES.
 
+- PDO_PGSQL:
+  . getAttribute() can now retrieve the memory usage of query results.
+    PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE was added for this feature.
+
 - PGSQL:
   . pg_select, the conditions arguments accepts an empty array and is optional.
 

ext/pdo_pgsql/config.m4

@@ -67,6 +67,7 @@ if test "$PHP_PDO_PGSQL" != "no"; then
   LDFLAGS="-L$PGSQL_LIBDIR $LDFLAGS"
 
   AC_CHECK_LIB(pq, PQlibVersion,, AC_MSG_ERROR([Unable to build the PDO PostgreSQL driver: at least libpq 9.1 is required]))
+  AC_CHECK_LIB(pq, PQresultMemorySize, AC_DEFINE(HAVE_PG_RESULT_MEMORY_SIZE,1,[PostgreSQL 12 or later]))
 
   LIBS=$old_LIBS
   LDFLAGS=$old_LDFLAGS

ext/pdo_pgsql/pdo_pgsql.c

@@ -156,6 +156,9 @@ PHP_MINIT_FUNCTION(pdo_pgsql)
 	REGISTER_PDO_CLASS_CONST_LONG("PGSQL_TRANSACTION_INTRANS", (zend_long)PGSQL_TRANSACTION_INTRANS);
 	REGISTER_PDO_CLASS_CONST_LONG("PGSQL_TRANSACTION_INERROR", (zend_long)PGSQL_TRANSACTION_INERROR);
 	REGISTER_PDO_CLASS_CONST_LONG("PGSQL_TRANSACTION_UNKNOWN", (zend_long)PGSQL_TRANSACTION_UNKNOWN);
+#ifdef HAVE_PG_RESULT_MEMORY_SIZE
+	REGISTER_PDO_CLASS_CONST_LONG("PGSQL_ATTR_RESULT_MEMORY_SIZE", (zend_long)PDO_PGSQL_ATTR_RESULT_MEMORY_SIZE);
+#endif
 
 	PdoPgsql_ce = register_class_PdoPgsql(pdo_dbh_ce);
 	PdoPgsql_ce->create_object = pdo_dbh_new;

ext/pdo_pgsql/pdo_pgsql.stub.php

@@ -11,6 +11,11 @@ class PdoPgsql extends PDO
     /** @cvalue PDO_PGSQL_ATTR_DISABLE_PREPARES */
     public const int ATTR_DISABLE_PREPARES = UNKNOWN;
 
+#ifdef HAVE_PG_RESULT_MEMORY_SIZE
+    /** @cvalue PDO_PGSQL_ATTR_RESULT_MEMORY_SIZE */
+    public const int ATTR_RESULT_MEMORY_SIZE = UNKNOWN;
+#endif
+
     /** @cvalue PGSQL_TRANSACTION_IDLE */
     public const int TRANSACTION_IDLE = UNKNOWN;
 

ext/pdo_pgsql/pdo_pgsql_arginfo.h

@@ -705,6 +705,32 @@ static int pdo_pgsql_stmt_cursor_closer(pdo_stmt_t *stmt)
 	return 1;
 }
 
+static int pgsql_stmt_get_attr(pdo_stmt_t *stmt, zend_long attr, zval *val)
+{
+	pdo_pgsql_stmt *S = (pdo_pgsql_stmt*)stmt->driver_data;
+
+	switch (attr) {
+#ifdef HAVE_PG_RESULT_MEMORY_SIZE
+		case PDO_PGSQL_ATTR_RESULT_MEMORY_SIZE:
+			if(stmt->executed) {
+				ZVAL_LONG(val, PQresultMemorySize(S->result));
+			} else {
+				char *tmp;
+				spprintf(&tmp, 0, "statement '%s' has not been executed yet", S->stmt_name);
+
+				pdo_pgsql_error_stmt_msg(stmt, 0, "HY000", tmp);
+				efree(tmp);
+
+				ZVAL_NULL(val);
+			}
+			return 1;
+#endif
+
+		default:
+			return 0;
+	}
+}
+
 const struct pdo_stmt_methods pgsql_stmt_methods = {
 	pgsql_stmt_dtor,
 	pgsql_stmt_execute,
@@ -713,7 +739,7 @@ const struct pdo_stmt_methods pgsql_stmt_methods = {
 	pgsql_stmt_get_col,
 	pgsql_stmt_param_hook,
 	NULL, /* set_attr */
-	NULL, /* get_attr */
+	pgsql_stmt_get_attr,
 	pgsql_stmt_get_column_meta,
 	NULL,  /* next_rowset */
 	pdo_pgsql_stmt_cursor_closer

ext/pdo_pgsql/pgsql_statement.c

@@ -86,6 +86,7 @@ extern const struct pdo_stmt_methods pgsql_stmt_methods;
 
 enum {
 	PDO_PGSQL_ATTR_DISABLE_PREPARES = PDO_ATTR_DRIVER_SPECIFIC,
+	PDO_PGSQL_ATTR_RESULT_MEMORY_SIZE,
 };
 
 struct pdo_pgsql_lob_self {

ext/pdo_pgsql/php_pdo_pgsql_int.h

@@ -0,0 +1,45 @@
+--TEST--
+PDO PgSQL PDOStatement::getAttribute(PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE)
+--EXTENSIONS--
+pdo_pgsql
+--SKIPIF--
+<?php
+require __DIR__ . '/config.inc';
+require dirname(__DIR__, 2) . '/pdo/tests/pdo_test.inc';
+PDOTest::skip();
+if (!defined('PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE')) die('skip constant PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE does not exist');
+--FILE--
+<?php
+
+require_once __DIR__ . "/config.inc";
+
+/** @var Pdo */
+$db =  Pdo::connect($config['ENV']['PDOTEST_DSN']);
+
+echo 'Result set with only 1 row: ';
+$statement = $db->query('select 1');
+$result_1 = $statement->getAttribute(PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE);
+var_dump($result_1);
+
+echo 'Result set with many rows: ';
+$result = $db->query('select generate_series(1, 10000)');
+$result_2 = $result->getAttribute(PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE);
+var_dump($result_2);
+
+echo 'Large result sets should require more memory than small ones: ';
+var_dump($result_2 > $result_1);
+
+echo 'Statements that are not executed should not consume memory: ';
+$statement = $db->prepare('select 1');
+$result_3 = $statement->getAttribute(PDO::PGSQL_ATTR_RESULT_MEMORY_SIZE);
+var_dump($result_3);
+
+echo 'and should emit Error: ';
+printf("%s: %d: %s\n", ...$statement->errorInfo());
+
+--EXPECTF--
+Result set with only 1 row: int(%d)
+Result set with many rows: int(%d)
+Large result sets should require more memory than small ones: bool(true)
+Statements that are not executed should not consume memory: NULL
+and should emit Error: HY000: 0: statement '%s' has not been executed yet