From 171c457cd06051b5910cf357ea6a77643b69088a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 10 Nov 2020 22:51:19 -0500 Subject: Fix and simplify some usages of TimestampDifference(). Introduce TimestampDifferenceMilliseconds() to simplify callers that would rather have the difference in milliseconds, instead of the select()-oriented seconds-and-microseconds format. This gets rid of at least one integer division per call, and it eliminates some apparently-easy-to-mess-up arithmetic. Two of these call sites were in fact wrong: * pg_prewarm's autoprewarm_main() forgot to multiply the seconds by 1000, thus ending up with a delay 1000X shorter than intended. That doesn't quite make it a busy-wait, but close. * postgres_fdw's pgfdw_get_cleanup_result() thought it needed to compute microseconds not milliseconds, thus ending up with a delay 1000X longer than intended. Somebody along the way had noticed this problem but misdiagnosed the cause, and imposed an ad-hoc 60-second limit rather than fixing the units. This was relatively harmless in context, because we don't care that much about exactly how long this delay is; still, it's wrong. There are a few more callers of TimestampDifference() that don't have a direct need for seconds-and-microseconds, but can't use TimestampDifferenceMilliseconds() either because they do need microsecond precision or because they might possibly deal with intervals long enough to overflow 32-bit milliseconds. It might be worth inventing another API to improve that, but that seems outside the scope of this patch; so those callers are untouched here. Given the fact that we are fixing some bugs, and the likelihood that future patches might want to back-patch code that uses this new API, back-patch to all supported branches. Alexey Kondratov and Tom Lane Discussion: https://postgr.es/m/3b1c053a21c07c1ed5e00be3b2b855ef@postgrespro.ru --- contrib/postgres_fdw/connection.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) (limited to 'contrib/postgres_fdw/connection.c') diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c index 9ef2d1336ef..f382203b8f3 100644 --- a/contrib/postgres_fdw/connection.c +++ b/contrib/postgres_fdw/connection.c @@ -1140,20 +1140,15 @@ pgfdw_get_cleanup_result(PGconn *conn, TimestampTz endtime, PGresult **result) { int wc; TimestampTz now = GetCurrentTimestamp(); - long secs; - int microsecs; long cur_timeout; /* If timeout has expired, give up, else get sleep time. */ - if (now >= endtime) + cur_timeout = TimestampDifferenceMilliseconds(now, endtime); + if (cur_timeout <= 0) { timed_out = true; goto exit; } - TimestampDifference(now, endtime, &secs, µsecs); - - /* To protect against clock skew, limit sleep to one minute. */ - cur_timeout = Min(60000, secs * USECS_PER_SEC + microsecs); /* Sleep until there's something to do */ wc = WaitLatchOrSocket(MyLatch, -- cgit v1.2.3