SNOW-1887475 possible fix OOM issue

snowflake_stmt.c

@@ -303,6 +303,10 @@ static int pdo_snowflake_stmt_describe(pdo_stmt_t *stmt, int colno) /* {{{ */
                 cols[i].maxlen = (size_t) F[i].byte_size;
                 break;
         }
+        if (cols[i].name)
+        {
+            zend_string_release(cols[i].name);
+        }
         cols[i].name = zend_string_init(
           F[i].name, strlen(F[i].name), 0);
 #if (PHP_VERSION_ID < 80100)

tests/memory_usage.phpt

@@ -0,0 +1,94 @@
+--TEST--
+pdo_snowflake - memory usage
+--INI--
+pdo_snowflake.logdir=sflog
+pdo_snowflake.loglevel=DEBUG
+pdo_snowflake.cacert=libsnowflakeclient/cacert.pem
+--FILE--
+<?php
+    include __DIR__ . "/common.php";
+
+    $dbh = new PDO($dsn, $user, $password);
+    $mem_usage_org = 0;
+    for ($i = 0; $i < 5; $i++) {
+        #collect original memory usage with second one since there is memory usage for one time initialize
+        # in the first one.
+        if ($i == 1)
+        {
+            $mem_usage_org = memory_get_usage();
+        }
+        try {
+            echo 'Memory usage before connection: ' . memory_get_usage() . "\n";
+            $pdo = new PDO($dsn, $user, $password);
+            $pdo->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
+            $query = 'SELECT * FROM SNOWFLAKE_SAMPLE_DATA.TPCH_SF1000.ORDERS LIMIT 10000';
+
+            echo 'Memory usage before query execution: ' . memory_get_usage() . "\n";
+            $stmt = $pdo->prepare($query);
+            $stmt->execute();
+            echo 'Memory usage before fetching: ' . memory_get_usage() . "\n";
+            $records = $stmt->fetchAll(PDO::FETCH_ASSOC);
+            echo 'Memory usage after fetching: ' . memory_get_usage() . "\n";
+        } catch (PDOException $e) {
+            echo "Unexpected failure: " . $e->getMessage() . "\n";
+        } finally {
+            if ($records) {
+                $records = null;
+                echo 'Memory usage after fetching data cleaning: ' . memory_get_usage() . "\n";
+            }
+            if ($stmt) {
+                $stmt = null;
+                echo 'Memory usage after stmt cleaning: ' . memory_get_usage() . "\n";
+            }
+            if ($pdo) {
+                $pdo = null;
+                echo 'Memory usage after pdo cleaning: ' . memory_get_usage() . "\n";
+            }
+        }
+        if (($mem_usage_org > 0) && (memory_get_usage() > $mem_usage_org))
+        {
+            echo 'Possible memory leak: original: ' . $mem_usage_org. 'current: ' . memory_get_usage() . "\n";
+        }
+    }
+    $dbh = null;
+?>
+===DONE===
+<?php exit(0); ?>
+--EXPECTF--
+Memory usage before connection: %s
+Memory usage before query execution: %s
+Memory usage before fetching: %s
+Memory usage after fetching: %s
+Memory usage after fetching data cleaning: %s
+Memory usage after stmt cleaning: %s
+Memory usage after pdo cleaning: %s
+Memory usage before connection: %s
+Memory usage before query execution: %s
+Memory usage before fetching: %s
+Memory usage after fetching: %s
+Memory usage after fetching data cleaning: %s
+Memory usage after stmt cleaning: %s
+Memory usage after pdo cleaning: %s
+Memory usage before connection: %s
+Memory usage before query execution: %s
+Memory usage before fetching: %s
+Memory usage after fetching: %s
+Memory usage after fetching data cleaning: %s
+Memory usage after stmt cleaning: %s
+Memory usage after pdo cleaning: %s
+Memory usage before connection: %s
+Memory usage before query execution: %s
+Memory usage before fetching: %s
+Memory usage after fetching: %s
+Memory usage after fetching data cleaning: %s
+Memory usage after stmt cleaning: %s
+Memory usage after pdo cleaning: %s
+Memory usage before connection: %s
+Memory usage before query execution: %s
+Memory usage before fetching: %s
+Memory usage after fetching: %s
+Memory usage after fetching data cleaning: %s
+Memory usage after stmt cleaning: %s
+Memory usage after pdo cleaning: %s
+===DONE===
+