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Implement ALTER TABLE ... MERGE PARTITIONS ... command

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This new DDL command merges several partitions into the one partition of the
target table.  The target partition is created using new
createPartitionTable() function with parent partition as the template.

This commit comprises quite naive implementation which works in single process
and holds the ACCESS EXCLUSIVE LOCK on the parent table during all the
operations including the tuple routing.  This is why this new DDL command
can't be recommended for large partitioned tables under a high load.  However,
this implementation come in handy in certain cases even as is.
Also, it could be used as a foundation for future implementations with lesser
locking and possibly parallel.

Discussion: https://postgr.es/m/c73a1746-0cd0-6bdd-6b23-3ae0b7c0c582%40postgrespro.ru
Author: Dmitry Koval
Reviewed-by: Matthias van de Meent, Laurenz Albe, Zhihong Yu, Justin Pryzby
Reviewed-by: Alvaro Herrera, Robert Haas, Stephane Tachoires
This commit is contained in:
Alexander Korotkov
2024-04-07 00:57:22 +03:00
parent fe1431e39c
commit 1adf16b8fb
17 changed files with 2189 additions and 22 deletions
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89
src/backend/parser/parse_utilcmd.c
View File

@ -58,6 +58,8 @@
#include "parser/parse_type.h"
#include "parser/parse_utilcmd.h"
#include "parser/parser.h"
#include "partitioning/partdesc.h"
#include "partitioning/partbounds.h"
#include "rewrite/rewriteManip.h"
#include "utils/acl.h"
#include "utils/builtins.h"
@ -3413,6 +3415,80 @@ transformRuleStmt(RuleStmt *stmt, const char *queryString,
}
/*
* transformPartitionCmdForMerge
* Analyze the ALTER TABLLE ... MERGE PARTITIONS command
*
* Does simple checks for merged partitions. Calculates bound of result
* partition.
*/
static void
transformPartitionCmdForMerge(CreateStmtContext *cxt, PartitionCmd *partcmd)
{
Oid defaultPartOid;
Oid partOid;
Relation parent = cxt->rel;
PartitionKey key;
char strategy;
ListCell *listptr,
*listptr2;
bool isDefaultPart = false;
List *partOids = NIL;
if (parent->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("\"%s\" is not a partitioned table", RelationGetRelationName(parent))));
key = RelationGetPartitionKey(parent);
strategy = get_partition_strategy(key);
if (strategy == PARTITION_STRATEGY_HASH)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("partition of hash-partitioned table cannot be merged")));
/* Is current partition a DEFAULT partition? */
defaultPartOid = get_default_oid_from_partdesc(
RelationGetPartitionDesc(parent, true));
foreach(listptr, partcmd->partlist)
{
RangeVar *name = (RangeVar *) lfirst(listptr);
/* Partitions in the list should have different names. */
for_each_cell(listptr2, partcmd->partlist, lnext(partcmd->partlist, listptr))
{
RangeVar *name2 = (RangeVar *) lfirst(listptr2);
if (equal(name, name2))
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_TABLE),
errmsg("partition with name \"%s\" already used", name->relname)),
parser_errposition(cxt->pstate, name2->location));
}
/* Search DEFAULT partition in the list. */
partOid = RangeVarGetRelid(name, NoLock, false);
if (partOid == defaultPartOid)
isDefaultPart = true;
partOids = lappend_oid(partOids, partOid);
}
/* Allocate bound of result partition. */
Assert(partcmd->bound == NULL);
partcmd->bound = makeNode(PartitionBoundSpec);
/* Fill partition bound. */
partcmd->bound->strategy = strategy;
partcmd->bound->location = -1;
partcmd->bound->is_default = isDefaultPart;
if (!isDefaultPart)
calculate_partition_bound_for_merge(parent, partcmd->partlist,
partOids, partcmd->bound,
cxt->pstate);
}
/*
* transformAlterTableStmt -
* parse analysis for ALTER TABLE
@ -3683,6 +3759,19 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
newcmds = lappend(newcmds, cmd);
break;
case AT_MergePartitions:
{
PartitionCmd *partcmd = (PartitionCmd *) cmd->def;
if (list_length(partcmd->partlist) < 2)
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("list of new partitions should contains at least two items")));
transformPartitionCmdForMerge(&cxt, partcmd);
newcmds = lappend(newcmds, cmd);
break;
}
default:
/*