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When creating a large hash index, pre-sort the index entries by estimated

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bucket number, so as to ensure locality of access to the index during the
insertion step.  Without this, building an index significantly larger than
available RAM takes a very long time because of thrashing.  On the other
hand, sorting is just useless overhead when the index does fit in RAM.
We choose to sort when the initial index size exceeds effective_cache_size.

This is a revised version of work by Tom Raney and Shreya Bhargava.
This commit is contained in:
Tom Lane
2008-03-16 23:15:08 +00:00
parent ec6550c6c0
commit 787eba734b
8 changed files with 324 additions and 39 deletions
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6
src/backend/access/nbtree/nbtsort.c
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@@ -57,7 +57,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtsort.c,v 1.114 2008/01/01 19:45:46 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtsort.c,v 1.115 2008/03/16 23:15:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -158,8 +158,8 @@ _bt_spoolinit(Relation index, bool isunique, bool isdead)
* work_mem.
*/
btKbytes = isdead ? work_mem : maintenance_work_mem;
btspool->sortstate = tuplesort_begin_index(index, isunique,
btKbytes, false);
btspool->sortstate = tuplesort_begin_index_btree(index, isunique,
btKbytes, false);
return btspool;
}