Optimize stroing zero FPI in WAL #327
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MMeent
reviewed
Nov 23, 2023
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+662
| bimg.hole_offset = 0; | ||
| cbimg.hole_length = BLCKSZ; |
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I'm fairly sure this doesn't result in a PageIsNew()-page during REDO.
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Why?
There is the following code in RestoreBlockImage:
/* generate page, taking into account hole if necessary */
if (bkpb->hole_length == 0)
{
memcpy(page, ptr, BLCKSZ);
}
else
{
memcpy(page, ptr, bkpb->hole_offset);
/* must zero-fill the hole */
MemSet(page + bkpb->hole_offset, 0, bkpb->hole_length);
memcpy(page + (bkpb->hole_offset + bkpb->hole_length),
ptr + bkpb->hole_offset,
BLCKSZ - (bkpb->hole_offset + bkpb->hole_length));
}
It is producing zero pages with hole_offset=0, hole_length=BLCKSZ, isn't it?
hlinnaka
approved these changes
Nov 23, 2023
|
Please describe the problem and how this fixes it in the commit message. |
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knizhnik
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Nov 29, 2023
## Problem PG16 (neondatabase/postgres#327) adds new function to SMGR: zeroextend It's implementation in Neon actually wal-log zero pages of extended relation. This zero page is wal-logged using XLOG_FPI. As far as page is zero, the hole optimization (excluding from the image everything between pg_upper and pd_lower) doesn't work. ## Summary of changes In case of zero page (`PageIsNull()` returns true) assume `hole_size=BLCKSZ` ## Checklist before requesting a review - [ ] I have performed a self-review of my code. - [ ] If it is a core feature, I have added thorough tests. - [ ] Do we need to implement analytics? if so did you add the relevant metrics to the dashboard? - [ ] If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section. ## Checklist before merging - [ ] Do not forget to reformat commit message to not include the above checklist --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
tristan957
pushed a commit
that referenced
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Dec 11, 2023
PG16 adds new function to SMGR: zeroextend It's implementation in Neon actually wal-log zero pages of extended relation. This zero page is wal-logged using XLOG_FPI. As far as page is zero, the hole optimization (excluding from the image everything between pg_upper and pd_lower) doesn't work. This PR allows to set hole size to BLCKSZ in case of zero page (PageIsNull() returns true). --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
tristan957
pushed a commit
that referenced
this pull request
Feb 5, 2024
PG16 adds new function to SMGR: zeroextend It's implementation in Neon actually wal-log zero pages of extended relation. This zero page is wal-logged using XLOG_FPI. As far as page is zero, the hole optimization (excluding from the image everything between pg_upper and pd_lower) doesn't work. This PR allows to set hole size to BLCKSZ in case of zero page (PageIsNull() returns true). --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
tristan957
pushed a commit
that referenced
this pull request
Feb 5, 2024
PG16 adds new function to SMGR: zeroextend It's implementation in Neon actually wal-log zero pages of extended relation. This zero page is wal-logged using XLOG_FPI. As far as page is zero, the hole optimization (excluding from the image everything between pg_upper and pd_lower) doesn't work. This PR allows to set hole size to BLCKSZ in case of zero page (PageIsNull() returns true). --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
tristan957
pushed a commit
that referenced
this pull request
Feb 6, 2024
PG16 adds new function to SMGR: zeroextend It's implementation in Neon actually wal-log zero pages of extended relation. This zero page is wal-logged using XLOG_FPI. As far as page is zero, the hole optimization (excluding from the image everything between pg_upper and pd_lower) doesn't work. This PR allows to set hole size to BLCKSZ in case of zero page (PageIsNull() returns true). --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
tristan957
pushed a commit
that referenced
this pull request
May 10, 2024
PG16 adds new function to SMGR: zeroextend It's implementation in Neon actually wal-log zero pages of extended relation. This zero page is wal-logged using XLOG_FPI. As far as page is zero, the hole optimization (excluding from the image everything between pg_upper and pd_lower) doesn't work. This PR allows to set hole size to BLCKSZ in case of zero page (PageIsNull() returns true). --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
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See https://neondb.slack.com/archives/C04DGM6SMTM/p1700654253600399