Fix compatibility with PostgreSQL 9.x: rows affected.

PiotrSikora · PiotrSikora · commit 7c1cde332912 · 2011-11-10T08:17:48.000Z
Starting with PostgreSQL 9.0, libpq's PQcmdTuples() returns row count
for SELECT queries (previously it returned empty string).

Because we're using this value to detect number of changed rows,
both: "postgres_rewrite" directive and "$postgres_affected" variable
were working incorrectly.

Reported by Yichun Zhang (agentzh).
diff --git a/src/ngx_postgres_processor.c b/src/ngx_postgres_processor.c
@@ -353,10 +353,12 @@ ngx_postgres_process_response(ngx_http_request_t *r, PGresult *res)
     pgctx->var_rows = PQntuples(res);
 
     /* set $postgres_affected */
-    affected = PQcmdTuples(res);
-    affected_len = ngx_strlen(affected);
-    if (affected_len) {
-        pgctx->var_affected = ngx_atoi((u_char *) affected, affected_len);
+    if (ngx_strncmp(PQcmdStatus(res), "SELECT", sizeof("SELECT") - 1)) {
+        affected = PQcmdTuples(res);
+        affected_len = ngx_strlen(affected);
+        if (affected_len) {
+            pgctx->var_affected = ngx_atoi((u_char *) affected, affected_len);
+        }
     }
 
     if (pglcf->rewrites) {
