2008-12-03 14:05:22 +01:00
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/*-------------------------------------------------------------------------
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*
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* visibilitymap.h
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* visibility map interface
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*
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*
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2023-01-02 21:00:37 +01:00
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* Portions Copyright (c) 2007-2023, PostgreSQL Global Development Group
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2008-12-03 14:05:22 +01:00
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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2010-09-20 22:08:53 +02:00
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* src/include/access/visibilitymap.h
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2008-12-03 14:05:22 +01:00
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef VISIBILITYMAP_H
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#define VISIBILITYMAP_H
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2021-09-23 18:59:03 +02:00
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#include "access/visibilitymapdefs.h"
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2008-12-03 14:05:22 +01:00
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#include "access/xlogdefs.h"
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2009-08-24 04:18:32 +02:00
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#include "storage/block.h"
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#include "storage/buf.h"
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#include "utils/relcache.h"
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2008-12-03 14:05:22 +01:00
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Change the format of the VM fork to add a second bit per page.
The new bit indicates whether every tuple on the page is already frozen.
It is cleared only when the all-visible bit is cleared, and it can be
set only when we vacuum a page and find that every tuple on that page is
both visible to every transaction and in no need of any future
vacuuming.
A future commit will use this new bit to optimize away full-table scans
that would otherwise be triggered by XID wraparound considerations. A
page which is merely all-visible must still be scanned in that case, but
a page which is all-frozen need not be. This commit does not attempt
that optimization, although that optimization is the goal here. It
seems better to get the basic infrastructure in place first.
Per discussion, it's very desirable for pg_upgrade to automatically
migrate existing VM forks from the old format to the new format. That,
too, will be handled in a follow-on patch.
Masahiko Sawada, reviewed by Kyotaro Horiguchi, Fujii Masao, Amit
Kapila, Simon Riggs, Andres Freund, and others, and substantially
revised by me.
2016-03-02 03:49:41 +01:00
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/* Macros for visibilitymap test */
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#define VM_ALL_VISIBLE(r, b, v) \
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((visibilitymap_get_status((r), (b), (v)) & VISIBILITYMAP_ALL_VISIBLE) != 0)
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#define VM_ALL_FROZEN(r, b, v) \
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((visibilitymap_get_status((r), (b), (v)) & VISIBILITYMAP_ALL_FROZEN) != 0)
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2016-07-18 11:01:13 +02:00
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extern bool visibilitymap_clear(Relation rel, BlockNumber heapBlk,
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Buffer vmbuf, uint8 flags);
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2008-12-03 14:05:22 +01:00
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extern void visibilitymap_pin(Relation rel, BlockNumber heapBlk,
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Buffer *vmbuf);
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Make the visibility map crash-safe.
This involves two main changes from the previous behavior. First,
when we set a bit in the visibility map, emit a new WAL record of type
XLOG_HEAP2_VISIBLE. Replay sets the page-level PD_ALL_VISIBLE bit and
the visibility map bit. Second, when inserting, updating, or deleting
a tuple, we can no longer get away with clearing the visibility map
bit after releasing the lock on the corresponding heap page, because
an intervening crash might leave the visibility map bit set and the
page-level bit clear. Making this work requires a bit of interface
refactoring.
In passing, a few minor but related cleanups: change the test in
visibilitymap_set and visibilitymap_clear to throw an error if the
wrong page (or no page) is pinned, rather than silently doing nothing;
this case should never occur. Also, remove duplicate definitions of
InvalidXLogRecPtr.
Patch by me, review by Noah Misch.
2011-06-22 05:04:40 +02:00
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extern bool visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf);
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2013-03-22 14:54:07 +01:00
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extern void visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
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Change the format of the VM fork to add a second bit per page.
The new bit indicates whether every tuple on the page is already frozen.
It is cleared only when the all-visible bit is cleared, and it can be
set only when we vacuum a page and find that every tuple on that page is
both visible to every transaction and in no need of any future
vacuuming.
A future commit will use this new bit to optimize away full-table scans
that would otherwise be triggered by XID wraparound considerations. A
page which is merely all-visible must still be scanned in that case, but
a page which is all-frozen need not be. This commit does not attempt
that optimization, although that optimization is the goal here. It
seems better to get the basic infrastructure in place first.
Per discussion, it's very desirable for pg_upgrade to automatically
migrate existing VM forks from the old format to the new format. That,
too, will be handled in a follow-on patch.
Masahiko Sawada, reviewed by Kyotaro Horiguchi, Fujii Masao, Amit
Kapila, Simon Riggs, Andres Freund, and others, and substantially
revised by me.
2016-03-02 03:49:41 +01:00
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XLogRecPtr recptr, Buffer vmBuf, TransactionId cutoff_xid,
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uint8 flags);
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extern uint8 visibilitymap_get_status(Relation rel, BlockNumber heapBlk, Buffer *vmbuf);
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extern void visibilitymap_count(Relation rel, BlockNumber *all_visible, BlockNumber *all_frozen);
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Speedup truncations of relation forks.
When a relation is truncated, shared_buffers needs to be scanned
so that any buffers for the relation forks are invalidated in it.
Previously, shared_buffers was scanned for each relation forks, i.e.,
MAIN, FSM and VM, when VACUUM truncated off any empty pages
at the end of relation or TRUNCATE truncated the relation in place.
Since shared_buffers needed to be scanned multiple times,
it could take a long time to finish those commands especially
when shared_buffers was large.
This commit changes the logic so that shared_buffers is scanned only
one time for those three relation forks.
Author: Kirk Jamison
Reviewed-by: Masahiko Sawada, Thomas Munro, Alvaro Herrera, Takayuki Tsunakawa and Fujii Masao
Discussion: https://postgr.es/m/D09B13F772D2274BB348A310EE3027C64E2067@g01jpexmbkw24
2019-09-24 10:31:26 +02:00
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extern BlockNumber visibilitymap_prepare_truncate(Relation rel,
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BlockNumber nheapblocks);
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2008-12-03 14:05:22 +01:00
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#endif /* VISIBILITYMAP_H */
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