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Support deferrable uniqueness constraints.

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The current implementation fires an AFTER ROW trigger for each tuple that
looks like it might be non-unique according to the index contents at the
time of insertion.  This works well as long as there aren't many conflicts,
but won't scale to massive unique-key reassignments.  Improving that case
is a TODO item.

Dean Rasheed
This commit is contained in:
Tom Lane
2009-07-29 20:56:21 +00:00
parent 8504905793
commit 25d9bf2e3e
51 changed files with 1241 additions and 245 deletions
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32
src/include/access/genam.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/access/genam.h,v 1.78 2009/06/11 14:49:08 momjian Exp $
* $PostgreSQL: pgsql/src/include/access/genam.h,v 1.79 2009/07/29 20:56:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -85,6 +85,34 @@ typedef bool (*IndexBulkDeleteCallback) (ItemPointer itemptr, void *state);
typedef struct IndexScanDescData *IndexScanDesc;
typedef struct SysScanDescData *SysScanDesc;
/*
* Enumeration specifying the type of uniqueness check to perform in
* index_insert().
*
* UNIQUE_CHECK_YES is the traditional Postgres immediate check, possibly
* blocking to see if a conflicting transaction commits.
*
* For deferrable unique constraints, UNIQUE_CHECK_PARTIAL is specified at
* insertion time. The index AM should test if the tuple is unique, but
* should not throw error, block, or prevent the insertion if the tuple
* appears not to be unique. We'll recheck later when it is time for the
* constraint to be enforced. The AM must return true if the tuple is
* known unique, false if it is possibly non-unique. In the "true" case
* it is safe to omit the later recheck.
*
* When it is time to recheck the deferred constraint, a pseudo-insertion
* call is made with UNIQUE_CHECK_EXISTING. The tuple is already in the
* index in this case, so it should not be inserted again. Rather, just
* check for conflicting live tuples (possibly blocking).
*/
typedef enum IndexUniqueCheck
{
UNIQUE_CHECK_NO, /* Don't do any uniqueness checking */
UNIQUE_CHECK_YES, /* Enforce uniqueness at insertion time */
UNIQUE_CHECK_PARTIAL, /* Test uniqueness, but no error */
UNIQUE_CHECK_EXISTING /* Check if existing tuple is unique */
} IndexUniqueCheck;
/*
* generalized index_ interface routines (in indexam.c)
@@ -103,7 +131,7 @@ extern bool index_insert(Relation indexRelation,
Datum *values, bool *isnull,
ItemPointer heap_t_ctid,
Relation heapRelation,
bool check_uniqueness);
IndexUniqueCheck checkUnique);
extern IndexScanDesc index_beginscan(Relation heapRelation,
Relation indexRelation,