From fb7ed3889fa6fc0f4aa6718ffb6574801ad12484 Mon Sep 17 00:00:00 2001 From: Tom Lane <tgl@sss.pgh.pa.us> Date: Sat, 10 Sep 2016 13:49:04 -0400 Subject: [PATCH] Fix miserable coding in pg_stat_get_activity(). Commit dd1a3bccc replaced a test on whether a subroutine returned a null pointer with a test on whether &pointer->backendStatus was null. This accidentally failed to fail, at least on common compilers, because backendStatus is the first field in the struct; but it was surely trouble waiting to happen. Commit f91feba87 then messed things up further, changing the logic to local_beentry = pgstat_fetch_stat_local_beentry(curr_backend); if (!local_beentry) continue; beentry = &local_beentry->backendStatus; if (!beentry) { where the second "if" is now dead code, so that the intended behavior of printing a row with "<backend information not available>" cannot occur. I suspect this is all moot because pgstat_fetch_stat_local_beentry will never actually return null in this function's usage, but it's still very poor coding. Repair back to 9.4 where the original problem was introduced. --- src/backend/utils/adt/pgstatfuncs.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 44ccd37e998..688eea12a93 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -633,15 +633,13 @@ pg_stat_get_activity(PG_FUNCTION_ARGS) { /* Get specific pid slot */ local_beentry = pgstat_fetch_stat_local_beentry(*(int *) (funcctx->user_fctx)); - beentry = &local_beentry->backendStatus; } else { /* Get the next one in the list */ local_beentry = pgstat_fetch_stat_local_beentry(funcctx->call_cntr + 1); /* 1-based index */ - beentry = &local_beentry->backendStatus; } - if (!beentry) + if (!local_beentry) { int i; @@ -655,6 +653,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS) SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple)); } + beentry = &local_beentry->backendStatus; + /* Values available to all callers */ values[0] = ObjectIdGetDatum(beentry->st_databaseid); values[1] = Int32GetDatum(beentry->st_procpid);