ext/pgsql: adding pg_close_stmt.

up to postgresql 17, when done with a prepared statement, we could
release it with DEALLOCATE sql command which is fine ; until we want
to implement a cache solution based on statement ids.

Since PostgreSQL 17, PQclosePrepared uses internally the `close` protocol
allowing to reuse the statement name while still freeing it.
Since the close protocol implementation had been added on libpq within
this release, no way to reimplement it.

Author: devnexen

ext/pgsql/config.m4

@@ -33,6 +33,9 @@ if test "$PHP_PGSQL" != "no"; then
       [Define to 1 if libpq has the 'PQsetChunkedRowsMode' function (PostgreSQL
       17 or later).])],,
     [$PGSQL_LIBS])
+  PHP_CHECK_LIBRARY([pq], [PQclosePrepared],
+    [AC_DEFINE([HAVE_PG_CLOSE_STMT], [1], [PostgreSQL 17 or later])],,
+    [$PGSQL_LIBS])
 
   old_CFLAGS=$CFLAGS
   CFLAGS="$CFLAGS $PGSQL_CFLAGS"

ext/pgsql/pgsql.c

@@ -6256,3 +6256,39 @@ PHP_FUNCTION(pg_set_chunked_rows_size)
 	RETURN_BOOL(PQsetChunkedRowsMode(link->conn, (int)size) == 1);
 }
 #endif
+
+#if defined(HAVE_PG_CLOSE_STMT)
+PHP_FUNCTION(pg_close_stmt)
+{
+	zval *pgsql_link;
+	pgsql_link_handle *link;
+	PGresult *pgsql_result;
+	zend_string *stmt;
+
+	ZEND_PARSE_PARAMETERS_START(2, 2)
+		Z_PARAM_OBJECT_OF_CLASS(pgsql_link, pgsql_link_ce)
+		Z_PARAM_STR(stmt)
+	ZEND_PARSE_PARAMETERS_END();
+
+	if (ZSTR_LEN(stmt) == 0) {
+		zend_argument_value_error(2, "cannot be empty");
+		RETURN_THROWS();
+	}
+
+	link = Z_PGSQL_LINK_P(pgsql_link);
+	CHECK_PGSQL_LINK(link);
+
+	pgsql_result = PQclosePrepared(link->conn, ZSTR_VAL(stmt));
+
+	if (!pgsql_result) {
+		RETURN_FALSE;
+	} else {
+		pgsql_result_handle *pg_result;
+		object_init_ex(return_value, pgsql_result_ce);
+		pg_result = Z_PGSQL_RESULT_P(return_value);
+		pg_result->conn = link->conn;
+		pg_result->result = pgsql_result;
+		pg_result->row = 0;
+	}
+}
+#endif

ext/pgsql/pgsql.stub.php

@@ -970,6 +970,9 @@ function pg_socket_poll($socket, int $read, int $write, int $timeout = -1): int
 #ifdef HAVE_PG_SET_CHUNKED_ROWS_SIZE
     function pg_set_chunked_rows_size(Pgsql\Connection $connection, int $size): bool {}
 #endif
+#ifdef HAVE_PG_CLOSE_STMT
+    function pg_close_stmt(Pgsql\Connection $connection, string $statement_name): Pgsql\Result|false {}
+#endif
 }
 
 namespace PgSql {

ext/pgsql/pgsql_arginfo.h

@@ -0,0 +1,33 @@
+--TEST--
+PostgreSQL pg_close_stmt
+--EXTENSIONS--
+pgsql
+--SKIPIF--
+<?php include("inc/skipif.inc");
+if (!function_exists("pg_close_stmt")) die("skip pg_close_stmt unsupported");
+?>
+--FILE--
+<?php
+include('inc/config.inc');
+
+
+$query = 'SELECT $1::text IS NULL;';
+$params_null = [null];
+
+$db = pg_connect($conn_str);
+$res = pg_prepare($db, 'test', $query);
+
+$res = pg_execute($db, 'test', $params_null);
+$res = pg_close_stmt($db, 'test');
+var_dump($res !== null);
+var_dump(pg_result_status($res) === PGSQL_COMMAND_OK);
+pg_prepare($db, 'test', $query);
+$res = pg_execute($db, 'test', $params_null);
+pg_free_result($res);
+
+pg_close($db);
+
+?>
+--EXPECT--
+bool(true)
+bool(true)