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Cache smgrnblocks() results in recovery.

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Avoid repeatedly calling lseek(SEEK_END) during recovery by caching
the size of each fork.  For now, we can't use the same technique in
other processes, because we lack a shared invalidation mechanism.

Do this by generalizing the pre-existing caching used by FSM and VM
to support all forks.

Discussion: https://postgr.es/m/CAEepm%3D3SSw-Ty1DFcK%3D1rU-K6GSzYzfdD4d%2BZwapdN7dTa6%3DnQ%40mail.gmail.com
This commit is contained in:
Thomas Munro
2020-07-31 14:15:18 +12:00
parent e3931d01f3
commit c5315f4f44
6 changed files with 66 additions and 46 deletions
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12
src/include/storage/smgr.h
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@@ -45,15 +45,13 @@ typedef struct SMgrRelationData
struct SMgrRelationData **smgr_owner;
/*
* These next three fields are not actually used or manipulated by smgr,
* except that they are reset to InvalidBlockNumber upon a cache flush
* event (in particular, upon truncation of the relation). Higher levels
* store cached state here so that it will be reset when truncation
* happens. In all three cases, InvalidBlockNumber means "unknown".
* The following fields are reset to InvalidBlockNumber upon a cache flush
* event, and hold the last known size for each fork. This information is
* currently only reliable during recovery, since there is no cache
* invalidation for fork extension.
*/
BlockNumber smgr_targblock; /* current insertion target block */
BlockNumber smgr_fsm_nblocks; /* last known size of fsm fork */
BlockNumber smgr_vm_nblocks; /* last known size of vm fork */
BlockNumber smgr_cached_nblocks[MAX_FORKNUM + 1]; /* last known size */
/* additional public fields may someday exist here */