Pdo\Pgsql: optimize calls to foreach(columns of the same table) getColumnMeta()

- each call queried the DB to know the name associated with the table's OID:
  cache the result between two calls
- make pdo_pgsql_translate_oid_to_table higher-level,
  with the last parameter being the handle instead of the raw connection;
  thus the statement is cleaner, letting the handle do all memory handling on the table oid-to-name translation cache
  (which by the way is a driver feature more than a statement one)

Author: outtersg

ext/pdo_pgsql/pgsql_driver.c

@@ -252,6 +252,10 @@ static void pgsql_handle_closer(pdo_dbh_t *dbh) /* {{{ */
 			PQfinish(H->server);
 			H->server = NULL;
 		}
+		if (H->cached_table_name) {
+			efree(H->cached_table_name);
+			H->cached_table_name = NULL;
+		}
 		if (H->einfo.errmsg) {
 			pefree(H->einfo.errmsg, dbh->is_persistent);
 			H->einfo.errmsg = NULL;
@@ -1445,6 +1449,7 @@ static int pdo_pgsql_handle_factory(pdo_dbh_t *dbh, zval *driver_options) /* {{{
 
 	H->attached = 1;
 	H->pgoid = -1;
+	H->cached_table_oid = InvalidOid;
 
 	dbh->methods = &pgsql_methods;
 	dbh->alloc_own_columns = 1;

ext/pdo_pgsql/pgsql_statement.c

@@ -702,12 +702,23 @@ static int pgsql_stmt_get_col(pdo_stmt_t *stmt, int colno, zval *result, enum pd
 	return 1;
 }
 
-static zend_always_inline char * pdo_pgsql_translate_oid_to_table(Oid oid, PGconn *conn)
+static zend_always_inline char * pdo_pgsql_translate_oid_to_table(Oid oid, pdo_pgsql_db_handle *H)
 {
+	PGconn *conn = H->server;
 	char *table_name = NULL;
 	PGresult *tmp_res;
 	char *querystr = NULL;
 
+	if (oid == H->cached_table_oid) {
+		return H->cached_table_name;
+	}
+
+	if (H->cached_table_name) {
+		efree(H->cached_table_name);
+		H->cached_table_name = NULL;
+		H->cached_table_oid = InvalidOid;
+	}
+
 	spprintf(&querystr, 0, "SELECT RELNAME FROM PG_CLASS WHERE OID=%d", oid);
 
 	if ((tmp_res = PQexec(conn, querystr)) == NULL || PQresultStatus(tmp_res) != PGRES_TUPLES_OK) {
@@ -724,6 +735,8 @@ static zend_always_inline char * pdo_pgsql_translate_oid_to_table(Oid oid, PGcon
 		return 0;
 	}
 
+	H->cached_table_oid = oid;
+	H->cached_table_name = estrdup(table_name);
 	table_name = estrdup(table_name);
 
 	PQclear(tmp_res);
@@ -752,10 +765,9 @@ static int pgsql_stmt_get_column_meta(pdo_stmt_t *stmt, zend_long colno, zval *r
 
 	table_oid = PQftable(S->result, colno);
 	add_assoc_long(return_value, "pgsql:table_oid", table_oid);
-	table_name = pdo_pgsql_translate_oid_to_table(table_oid, S->H->server);
+	table_name = pdo_pgsql_translate_oid_to_table(table_oid, S->H);
 	if (table_name) {
-		add_assoc_string(return_value, "table", table_name);
-		efree(table_name);
+		add_assoc_string(return_value, "table", S->H->cached_table_name);
 	}
 
 	switch (S->cols[colno].pgsql_type) {

ext/pdo_pgsql/php_pdo_pgsql_int.h

@@ -43,6 +43,8 @@ typedef struct {
 	unsigned 	_reserved:31;
 	pdo_pgsql_error_info	einfo;
 	Oid 		pgoid;
+	Oid cached_table_oid;
+	char *cached_table_name;
 	unsigned int	stmt_counter;
 	/* The following two variables have the same purpose. Unfortunately we need
 	   to keep track of two different attributes having the same effect. */