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.

close phpGH-14584

NEWS

@@ -8,6 +8,10 @@ PHP                                                                        NEWS
     Pdo\Pgsql::prepare(…, [ PDO::ATTR_PREFETCH => 0 ]) make fetch() lazy
     instead of storing the whole result set in memory (Guillaume Outters)
 
+- PGSQL:
+  . Added pg_close_stmt to close a prepared statement while allowing
+    its name to be reused. (David Carlier)
+
 - Random:
   . Moves from /dev/urandom usage to arc4random_buf on Haiku. (David Carlier)
 

UPGRADING

@@ -59,6 +59,11 @@ PHP 8.5 UPGRADE NOTES
 6. New Functions
 ========================================
 
+- PGSQL@
+  . pg_close_stmt offers an alternative way to close a prepared
+    statement from the DEALLOCATE sql command in that we can reuse
+    its name afterwards.
+
 ========================================
 7. New Classes and Interfaces
 ========================================

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 (PQresultStatus(pgsql_result) != PGRES_COMMAND_OK) {
+		RETURN_FALSE;
+	} else {
+		pgsql_result_handle *pg_handle;
+		object_init_ex(return_value, pgsql_result_ce);
+		pg_handle = Z_PGSQL_RESULT_P(return_value);
+		pg_handle->conn = link->conn;
+		pg_handle->result = pgsql_result;
+		pg_handle->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/tests/pg_close_stmt.phpt

@@ -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 !== false);
+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)