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Add the "snapshot too old" feature

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This feature is controlled by a new old_snapshot_threshold GUC.  A
value of -1 disables the feature, and that is the default.  The
value of 0 is just intended for testing.  Above that it is the
number of minutes a snapshot can reach before pruning and vacuum
are allowed to remove dead tuples which the snapshot would
otherwise protect.  The xmin associated with a transaction ID does
still protect dead tuples.  A connection which is using an "old"
snapshot does not get an error unless it accesses a page modified
recently enough that it might not be able to produce accurate
results.

This is similar to the Oracle feature, and we use the same SQLSTATE
and error message for compatibility.
This commit is contained in:
Kevin Grittner
2016-04-08 14:36:30 -05:00
parent 8b65cf4c5e
commit 848ef42bb8
41 changed files with 942 additions and 85 deletions
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4
src/include/access/gin_private.h
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@ -703,7 +703,7 @@ typedef struct
* PostingItem
*/
extern GinBtreeStack *ginFindLeafPage(GinBtree btree, bool searchMode);
extern GinBtreeStack *ginFindLeafPage(GinBtree btree, bool searchMode, Snapshot snapshot);
extern Buffer ginStepRight(Buffer buffer, Relation index, int lockmode);
extern void freeGinBtreeStack(GinBtreeStack *stack);
extern void ginInsertValue(GinBtree btree, GinBtreeStack *stack,
@ -731,7 +731,7 @@ extern void GinPageDeletePostingItem(Page page, OffsetNumber offset);
extern void ginInsertItemPointers(Relation index, BlockNumber rootBlkno,
ItemPointerData *items, uint32 nitem,
GinStatsData *buildStats);
extern GinBtreeStack *ginScanBeginPostingTree(GinBtree btree, Relation index, BlockNumber rootBlkno);
extern GinBtreeStack *ginScanBeginPostingTree(GinBtree btree, Relation index, BlockNumber rootBlkno, Snapshot snapshot);
extern void ginDataFillRoot(GinBtree btree, Page root, BlockNumber lblkno, Page lpage, BlockNumber rblkno, Page rpage);
extern void ginPrepareDataScan(GinBtree btree, Relation index, BlockNumber rootBlkno);