From ddc889317912fd8b654439701195a43cecfd4e79 Mon Sep 17 00:00:00 2001 From: Tom Lane 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 "" 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 | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 5d1ccf51d4..2d3cf9e468 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -688,27 +688,17 @@ pg_stat_get_activity(PG_FUNCTION_ARGS) MemSet(values, 0, sizeof(values)); MemSet(nulls, 0, sizeof(nulls)); - if (pid != -1) - { - /* Skip any which are not the one we're looking for. */ - PgBackendStatus *be = pgstat_fetch_stat_beentry(curr_backend); - - if (!be || be->st_procpid != pid) - continue; - - } - /* Get the next one in the list */ local_beentry = pgstat_fetch_stat_local_beentry(curr_backend); if (!local_beentry) - continue; - - beentry = &local_beentry->backendStatus; - if (!beentry) { int i; - for (i = 0; i < sizeof(nulls) / sizeof(nulls[0]); i++) + /* Ignore missing entries if looking for specific PID */ + if (pid != -1) + continue; + + for (i = 0; i < lengthof(nulls); i++) nulls[i] = true; nulls[5] = false; @@ -718,6 +708,12 @@ pg_stat_get_activity(PG_FUNCTION_ARGS) continue; } + beentry = &local_beentry->backendStatus; + + /* If looking for specific PID, ignore all the others */ + if (pid != -1 && beentry->st_procpid != pid) + continue; + /* Values available to all callers */ values[0] = ObjectIdGetDatum(beentry->st_databaseid); values[1] = Int32GetDatum(beentry->st_procpid); -- 2.40.0