2017-04-04 19:18 GMT+02:00 Scott Marlowe <scott.marl...@gmail.com>: > On Tue, Apr 4, 2017 at 9:46 AM, Tom DalPozzo <t.dalpo...@gmail.com> wrote: > > Hi, > > I have a very big table (10GB). > > I noticed that many WAL segments are being written when elaborating read > > only transactions like this: > > select * from dati25600000000 where id >43000000 limit 1000000; > > I don't understand why are there WAL writings during read only > transactions. > > Regards > > Pupillo > > > > I think this is the db setting hint bits, but I'm no expert in that area. >
Hi, I'm not able to reproduce the problem in a deterministic way. Sometimes it does sometimes not. Anyway, examining with pg_xlogdum those WAL, I get many many records like these: rmgr: XLOG len (rec/tot): 0/ 8173, tx: 0, lsn: C/E502AF28, prev C/E5028F20, desc: FPI_FOR_HINT , blkref #0: rel 1663/16384/18846 blk 1454439 FPW rmgr: XLOG len (rec/tot): 0/ 8173, tx: 0, lsn: C/E502CF30, prev C/E502AF28, desc: FPI_FOR_HINT , blkref #0: rel 1663/16384/18846 blk 1454440 FPW rmgr: XLOG len (rec/tot): 0/ 8173, tx: 0, lsn: C/E502EF38, prev C/E502CF30, desc: FPI_FOR_HINT , blkref #0: rel 1663/16384/18846 blk 1454441 FPW rmgr: XLOG len (rec/tot): 0/ 8173, tx: 0, lsn: C/E5030F40, prev C/E502EF38, desc: FPI_FOR_HINT , blkref #0: rel 1663/16384/18846 blk 1454442 FPW rmgr: XLOG len (rec/tot): 0/ 8173, tx: 0, lsn: C/E5032F48, prev C/E5030F40, desc: FPI_FOR_HINT , blkref #0: rel 1663/16384/18846 blk 1454443 FPW What is the meaning of FPI_FOR_HINT? I've replication slots and async replication, but slaves are kept off (PCs not powered). No other queries except that one. Even select count (*) from dati25600000000; gives the problem (sometimes) Thanks Pupillo
