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Add hash partitioning.

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Hash partitioning is useful when you want to partition a growing data
set evenly.  This can be useful to keep table sizes reasonable, which
makes maintenance operations such as VACUUM faster, or to enable
partition-wise join.

At present, we still depend on constraint exclusion for partitioning
pruning, and the shape of the partition constraints for hash
partitioning is such that that doesn't work.  Work is underway to fix
that, which should both improve performance and make partitioning
pruning work with hash partitioning.

Amul Sul, reviewed and tested by Dilip Kumar, Ashutosh Bapat, Yugo
Nagata, Rajkumar Raghuwanshi, Jesper Pedersen, and by me.  A few
final tweaks also by me.

Discussion: http://postgr.es/m/CAAJ_b96fhpJAP=ALbETmeLk1Uni_GFZD938zgenhF49qgDTjaQ@mail.gmail.com
This commit is contained in:
Robert Haas
2017-11-09 18:07:25 -05:00
parent e7397f015c
commit 1aba8e651a
30 changed files with 1421 additions and 121 deletions
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15
src/backend/utils/adt/ruleutils.c
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@ -1551,7 +1551,7 @@ pg_get_statisticsobj_worker(Oid statextid, bool missing_ok)
*
* Returns the partition key specification, ie, the following:
*
* PARTITION BY { RANGE | LIST } (column opt_collation opt_opclass [, ...])
* PARTITION BY { RANGE | LIST | HASH } (column opt_collation opt_opclass [, ...])
*/
Datum
pg_get_partkeydef(PG_FUNCTION_ARGS)
@ -1655,6 +1655,10 @@ pg_get_partkeydef_worker(Oid relid, int prettyFlags,
switch (form->partstrat)
{
case PARTITION_STRATEGY_HASH:
if (!attrsOnly)
appendStringInfo(&buf, "HASH");
break;
case PARTITION_STRATEGY_LIST:
if (!attrsOnly)
appendStringInfoString(&buf, "LIST");
@ -8711,6 +8715,15 @@ get_rule_expr(Node *node, deparse_context *context,
switch (spec->strategy)
{
case PARTITION_STRATEGY_HASH:
Assert(spec->modulus > 0 && spec->remainder >= 0);
Assert(spec->modulus > spec->remainder);
appendStringInfoString(buf, "FOR VALUES");
appendStringInfo(buf, " WITH (modulus %d, remainder %d)",
spec->modulus, spec->remainder);
break;
case PARTITION_STRATEGY_LIST:
Assert(spec->listdatums != NIL);