database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-09-02 04:21:28 +03:00
Code Activity

Add support for MERGE SQL command

Browse Source 
MERGE performs actions that modify rows in the target table using a
source table or query. MERGE provides a single SQL statement that can
conditionally INSERT/UPDATE/DELETE rows -- a task that would otherwise
require multiple PL statements.  For example,

MERGE INTO target AS t
USING source AS s
ON t.tid = s.sid
WHEN MATCHED AND t.balance > s.delta THEN
  UPDATE SET balance = t.balance - s.delta
WHEN MATCHED THEN
  DELETE
WHEN NOT MATCHED AND s.delta > 0 THEN
  INSERT VALUES (s.sid, s.delta)
WHEN NOT MATCHED THEN
  DO NOTHING;

MERGE works with regular tables, partitioned tables and inheritance
hierarchies, including column and row security enforcement, as well as
support for row and statement triggers and transition tables therein.

MERGE is optimized for OLTP and is parameterizable, though also useful
for large scale ETL/ELT. MERGE is not intended to be used in preference
to existing single SQL commands for INSERT, UPDATE or DELETE since there
is some overhead.  MERGE can be used from PL/pgSQL.

MERGE does not support targetting updatable views or foreign tables, and
RETURNING clauses are not allowed either.  These limitations are likely
fixable with sufficient effort.  Rewrite rules are also not supported,
but it's not clear that we'd want to support them.

Author: Pavan Deolasee <pavan.deolasee@gmail.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Simon Riggs <simon.riggs@enterprisedb.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier versions)
Reviewed-by: Peter Geoghegan <pg@bowt.ie> (earlier versions)
Reviewed-by: Robert Haas <robertmhaas@gmail.com> (earlier versions)
Reviewed-by: Japin Li <japinli@hotmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Discussion: https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.com
Discussion: https://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com
Discussion: https://postgr.es/m/20201231134736.GA25392@alvherre.pgsql
This commit is contained in:
Alvaro Herrera
2022-03-28 16:45:58 +02:00
parent ae63017bdb
commit 7103ebb7aa
95 changed files with 8726 additions and 167 deletions
Download Patch File Download Diff File Expand all files Collapse all files

91
src/backend/optimizer/prep/prepjointree.c
View File

@@ -132,6 +132,86 @@ static void fix_append_rel_relids(List *append_rel_list, int varno,
static Node *find_jointree_node_for_rel(Node *jtnode, int relid);
/*
* transform_MERGE_to_join
* Replace a MERGE's jointree to also include the target relation.
*/
void
transform_MERGE_to_join(Query *parse)
{
RangeTblEntry *joinrte;
JoinExpr *joinexpr;
JoinType jointype;
int joinrti;
List *vars;
if (parse->commandType != CMD_MERGE)
return;
/* XXX probably bogus */
vars = NIL;
/*
* When any WHEN NOT MATCHED THEN INSERT clauses exist, we need to use an
* outer join so that we process all unmatched tuples from the source
* relation. If none exist, we can use an inner join.
*/
if (parse->mergeUseOuterJoin)
jointype = JOIN_RIGHT;
else
jointype = JOIN_INNER;
/* Manufacture a join RTE to use. */
joinrte = makeNode(RangeTblEntry);
joinrte->rtekind = RTE_JOIN;
joinrte->jointype = jointype;
joinrte->joinmergedcols = 0;
joinrte->joinaliasvars = vars;
joinrte->joinleftcols = NIL; /* MERGE does not allow JOIN USING */
joinrte->joinrightcols = NIL; /* ditto */
joinrte->join_using_alias = NULL;
joinrte->alias = NULL;
joinrte->eref = makeAlias("*MERGE*", NIL);
joinrte->lateral = false;
joinrte->inh = false;
joinrte->inFromCl = true;
joinrte->requiredPerms = 0;
joinrte->checkAsUser = InvalidOid;
joinrte->selectedCols = NULL;
joinrte->insertedCols = NULL;
joinrte->updatedCols = NULL;
joinrte->extraUpdatedCols = NULL;
joinrte->securityQuals = NIL;
/*
* Add completed RTE to pstate's range table list, so that we know its
* index.
*/
parse->rtable = lappend(parse->rtable, joinrte);
joinrti = list_length(parse->rtable);
/*
* Create a JOIN between the target and the source relation.
*/
joinexpr = makeNode(JoinExpr);
joinexpr->jointype = jointype;
joinexpr->isNatural = false;
joinexpr->larg = (Node *) makeNode(RangeTblRef);
((RangeTblRef *) joinexpr->larg)->rtindex = parse->resultRelation;
joinexpr->rarg = linitial(parse->jointree->fromlist); /* original join */
joinexpr->usingClause = NIL;
joinexpr->join_using_alias = NULL;
/* The quals are removed from the jointree and into this specific join */
joinexpr->quals = parse->jointree->quals;
joinexpr->alias = NULL;
joinexpr->rtindex = joinrti;
/* Make the new join be the sole entry in the query's jointree */
parse->jointree->fromlist = list_make1(joinexpr);
parse->jointree->quals = NULL;
}
/*
* replace_empty_jointree
* If the Query's jointree is empty, replace it with a dummy RTE_RESULT
@@ -2058,6 +2138,17 @@ perform_pullup_replace_vars(PlannerInfo *root,
* can't contain any references to a subquery.
*/
}
if (parse->mergeActionList)
{
foreach(lc, parse->mergeActionList)
{
MergeAction *action = lfirst(lc);
action->qual = pullup_replace_vars(action->qual, rvcontext);
action->targetList = (List *)
pullup_replace_vars((Node *) action->targetList, rvcontext);
}
}
replace_vars_in_jointree((Node *) parse->jointree, rvcontext,
lowest_nulling_outer_join);
Assert(parse->setOperations == NULL);

37
src/backend/optimizer/prep/preptlist.c
View File

@@ -124,6 +124,43 @@ preprocess_targetlist(PlannerInfo *root)
tlist = root->processed_tlist;
}
/*
* For MERGE we need to handle the target list for the target relation,
* and also target list for each action (only INSERT/UPDATE matter).
*/
if (command_type == CMD_MERGE)
{
ListCell *l;
/*
* For MERGE, add any junk column(s) needed to allow the executor to
* identify the rows to be inserted or updated.
*/
root->processed_tlist = tlist;
add_row_identity_columns(root, result_relation,
target_rte, target_relation);
tlist = root->processed_tlist;
/*
* For MERGE, handle targetlist of each MergeAction separately. Give
* the same treatment to MergeAction->targetList as we would have
* given to a regular INSERT. For UPDATE, collect the column numbers
* being modified.
*/
foreach(l, parse->mergeActionList)
{
MergeAction *action = (MergeAction *) lfirst(l);
if (action->commandType == CMD_INSERT)
action->targetList = expand_insert_targetlist(action->targetList,
target_relation);
else if (action->commandType == CMD_UPDATE)
action->updateColnos =
extract_update_targetlist_colnos(action->targetList);
}
}
/*
* Add necessary junk columns for rowmarked rels. These values are needed
* for locking of rels selected FOR UPDATE/SHARE, and to do EvalPlanQual