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Fix longstanding problems in VACUUM caused by untimely interruptions

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In VACUUM FULL, an interrupt after the initial transaction has been recorded
as committed can cause postmaster to restart with the following error message:
PANIC: cannot abort transaction NNNN, it was already committed
This problem has been reported many times.

In lazy VACUUM, an interrupt after the table has been truncated by
lazy_truncate_heap causes other backends' relcache to still point to the
removed pages; this can cause future INSERT and UPDATE queries to error out
with the following error message:
could not read block XX of relation 1663/NNN/MMMM: read only 0 of 8192 bytes
The window to this race condition is extremely narrow, but it has been seen in
the wild involving a cancelled autovacuum process.

The solution for both problems is to inhibit interrupts in both operations
until after the respective transactions have been committed.  It's not a
complete solution, because the transaction could theoretically be aborted by
some other error, but at least fixes the most common causes of both problems.
This commit is contained in:
Alvaro Herrera
2009-11-10 18:00:30 +00:00
parent 2c61405206
commit 83d4698cc9
3 changed files with 50 additions and 13 deletions
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4
src/include/commands/vacuum.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.85 2009/06/11 14:49:11 momjian Exp $
* $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.85.2.1 2009/11/10 18:00:30 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -146,7 +146,7 @@ extern bool vac_is_partial_index(Relation indrel);
extern void vacuum_delay_point(void);
/* in commands/vacuumlazy.c */
extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
extern bool lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
BufferAccessStrategy bstrategy, bool *scanned_all);
/* in commands/analyze.c */