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Combine two flag tests in GetSnapshotData(). 

Previously the code checked PROC_IN_LOGICAL_DECODING and
PROC_IN_VACUUM separately. As the relevant variable is marked as
volatile, the compiler cannot combine the two tests.  As
GetSnapshotData() is pretty hot in a number of workloads, it's
worthwhile to fix that.

It'd also be a good idea to get rid of the volatiles altogether. But
for one that's a larger patch, and for another, the code after this
change still seems at least as easy to read as before.

Author: Andres Freund
Discussion: https://postgr.es/m/20181005172955.wyjb4fzcdzqtaxjq@alap3.anarazel.de
This commit is contained in:
Andres Freund 2018-11-09 20:43:56 -08:00
parent 5fc1670bad
commit 5fde047f2b
1 changed files with 4 additions and 7 deletions
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11
src/backend/storage/ipc/procarray.c
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@ -1589,14 +1589,11 @@ GetSnapshotData(Snapshot snapshot)
TransactionId xid;
/*
* Backend is doing logical decoding which manages xmin
* separately, check below.
* Skip over backends doing logical decoding which manages xmin
* separately (check below) and ones running LAZY VACUUM.
*/
if (pgxact->vacuumFlags & PROC_IN_LOGICAL_DECODING)
continue;
/* Ignore procs running LAZY VACUUM */
if (pgxact->vacuumFlags & PROC_IN_VACUUM)
if (pgxact->vacuumFlags &
(PROC_IN_LOGICAL_DECODING | PROC_IN_VACUUM))
continue;
/* Update globalxmin to be the smallest valid xmin */