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Commit93078e6

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Maintain valid md.c state when FileClose() fails.
FileClose() failure ordinarily causes a PANIC. Suppose the userdisables that PANIC via data_sync_retry=on. After mdclose() issued aFileClose() that failed, calls into md.c raised SIGSEGV. This fix addsrepalloc() calls during mdclose(); update a comment about ignoringrepalloc() cost. The rate of relation segment count change is a minorfactor; more relevant to overall performance is the rate of mdclose()and subsequent re-opening of segments. Back-patch to v10, where commit45e191e introduced the bug.Reviewed by Kyotaro Horiguchi.Discussion:https://postgr.es/m/20191222091930.GA1280238@rfd.leadboat.com
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  • src/backend/storage/smgr

1 file changed

+6
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lines changed

‎src/backend/storage/smgr/md.c‎

Lines changed: 6 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -491,18 +491,10 @@ mdclose(SMgrRelation reln, ForkNumber forknum)
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{
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MdfdVec*v=&reln->md_seg_fds[forknum][nopensegs-1];
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/* if not closed already */
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if (v->mdfd_vfd >=0)
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{
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FileClose(v->mdfd_vfd);
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v->mdfd_vfd=-1;
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}
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FileClose(v->mdfd_vfd);
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_fdvec_resize(reln,forknum,nopensegs-1);
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nopensegs--;
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}
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/* resize just once, avoids pointless reallocations */
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_fdvec_resize(reln,forknum,0);
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}
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/*
@@ -1025,10 +1017,10 @@ _fdvec_resize(SMgrRelation reln,
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else
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{
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/*
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* It doesn't seem worthwhile complicating the codeby having a more
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*aggressive growth strategy here; the number of segments doesn't
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*grow that fast, and the memory context internally will sometimes
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*avoiddoing an actual reallocation.
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* It doesn't seem worthwhile complicating the codeto amortize
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*repalloc() calls. Those are far faster than PathNameOpenFile() or
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*FileClose(), and the memory context internally will sometimes avoid
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* doing an actual reallocation.
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*/
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reln->md_seg_fds[forknum]=
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repalloc(reln->md_seg_fds[forknum],

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