pdo_pgsql: unbuffered fetching: now invokable

use Pdo::setAttribute(PDO::ATTR_PREFETCH, 0)

Author: outtersg

ext/pdo_pgsql/pgsql_driver.c

@@ -303,6 +303,8 @@ static bool pgsql_handle_preparer(pdo_dbh_t *dbh, zend_string *sql, pdo_stmt_t *
 		stmt->named_rewrite_template = "$%d";
 	}
 
+	S->is_unbuffered = H->default_fetching_laziness;
+
 	ret = pdo_parse_params(stmt, sql, &nsql);
 
 	if (ret == -1) {
@@ -1301,6 +1303,12 @@ static bool pdo_pgsql_set_attr(pdo_dbh_t *dbh, zend_long attr, zval *val)
 			}
 			H->disable_prepares = bval;
 			return true;
+		case PDO_ATTR_PREFETCH:
+			if (!pdo_get_bool_param(&bval, val)) {
+				return false;
+			}
+			H->default_fetching_laziness = !bval;
+			return true;
 		default:
 			return false;
 	}

ext/pdo_pgsql/pgsql_statement.c

@@ -60,13 +60,28 @@
 
 static void pgsql_stmt_cancel(pdo_pgsql_stmt *S)
 {
+	if (S->result) {
+		PQclear(S->result);
+		S->result = NULL;
+	}
+
 	if (S->is_running_unbuffered) {
 		PGcancel *cancel = PQgetCancel(S->H->server);
 		char errbuf[256];
 		PQcancel(cancel, errbuf, 256);
 		PQfreeCancel(cancel);
 		S->is_running_unbuffered = false;
 	}
+
+	if (S->is_unbuffered) {
+		/* https://postgresql.org/docs/current/libpq-async.html:
+		 * "PQsendQuery cannot be called again until PQgetResult has returned NULL"
+		 */
+		while ((S->result = PQgetResult(S->H->server))) {
+			PQclear(S->result);
+			S->result = NULL;
+		}
+	}
 }
 
 static int pgsql_stmt_dtor(pdo_stmt_t *stmt)
@@ -76,12 +91,6 @@ static int pgsql_stmt_dtor(pdo_stmt_t *stmt)
 		&& IS_OBJ_VALID(EG(objects_store).object_buckets[Z_OBJ_HANDLE(stmt->database_object_handle)])
 		&& !(OBJ_FLAGS(Z_OBJ(stmt->database_object_handle)) & IS_OBJ_FREE_CALLED);
 
-	if (S->result) {
-		/* free the resource */
-		PQclear(S->result);
-		S->result = NULL;
-	}
-
 	if (S->stmt_name) {
 		if (S->is_prepared && server_obj_usable) {
 			pdo_pgsql_db_handle *H = S->H;
@@ -156,10 +165,6 @@ static int pgsql_stmt_execute(pdo_stmt_t *stmt)
 
 	/* ensure that we free any previous unfetched results */
 	pgsql_stmt_cancel(S);
-	if(S->result) {
-		PQclear(S->result);
-		S->result = NULL;
-	}
 
 	S->current_row = 0;
 
@@ -541,10 +546,10 @@ static int pgsql_stmt_fetch(pdo_stmt_t *stmt,
 			S->current_row = 0;
 
 			if (!stmt->row_count) {
-				/* libpq requires looping until getResult returns null */
-				PQgetResult(S->H->server);
 				/* @todo receiving a result here is unexpected and should throw an error */
 				S->is_running_unbuffered = false;
+				/* libpq requires looping until getResult returns null */
+				pgsql_stmt_cancel(S);
 			}
 		}
 		if (S->current_row < stmt->row_count) {

ext/pdo_pgsql/php_pdo_pgsql_int.h

@@ -47,6 +47,7 @@ typedef struct {
 	bool		disable_prepares;
 	HashTable       *lob_streams;
 	zend_fcall_info_cache *notice_callback;
+	bool		default_fetching_laziness;
 } pdo_pgsql_db_handle;
 
 typedef struct {