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New files for MERGE
This commit is contained in:
Simon Riggs
660
src/backend/parser/parse_merge.c
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660
src/backend/parser/parse_merge.c
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@@ -0,0 +1,660 @@
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/*-------------------------------------------------------------------------
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*
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* parse_merge.c
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* handle merge-statement in parser
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*
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* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/parser/parse_merge.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "miscadmin.h"
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#include "access/sysattr.h"
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#include "nodes/makefuncs.h"
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#include "parser/analyze.h"
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#include "parser/parse_collate.h"
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#include "parser/parsetree.h"
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#include "parser/parser.h"
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#include "parser/parse_clause.h"
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#include "parser/parse_merge.h"
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#include "parser/parse_relation.h"
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#include "parser/parse_target.h"
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#include "utils/rel.h"
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#include "utils/relcache.h"
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static int transformMergeJoinClause(ParseState *pstate, Node *merge,
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List **mergeSourceTargetList);
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static void setNamespaceForMergeAction(ParseState *pstate,
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MergeAction *action);
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static void setNamespaceVisibilityForRTE(List *namespace, RangeTblEntry *rte,
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bool rel_visible,
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bool cols_visible);
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static List *expandSourceTL(ParseState *pstate, RangeTblEntry *rte,
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int rtindex);
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/*
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* Special handling for MERGE statement is required because we assemble
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* the query manually. This is similar to setTargetTable() followed
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* by transformFromClause() but with a few less steps.
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*
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* Process the FROM clause and add items to the query's range table,
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* joinlist, and namespace.
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*
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* A special targetlist comprising of the columns from the right-subtree of
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* the join is populated and returned. Note that when the JoinExpr is
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* setup by transformMergeStmt, the left subtree has the target result
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* relation and the right subtree has the source relation.
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*
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* Returns the rangetable index of the target relation.
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*/
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static int
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transformMergeJoinClause(ParseState *pstate, Node *merge,
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List **mergeSourceTargetList)
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{
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RangeTblEntry *rte,
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*rt_rte;
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List *namespace;
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int rtindex,
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rt_rtindex;
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Node *n;
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int mergeTarget_relation = list_length(pstate->p_rtable) + 1;
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Var *var;
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TargetEntry *te;
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n = transformFromClauseItem(pstate, merge,
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&rte,
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&rtindex,
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&rt_rte,
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&rt_rtindex,
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&namespace);
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pstate->p_joinlist = list_make1(n);
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/*
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* We created an internal join between the target and the source relation
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* to carry out the MERGE actions. Normally such an unaliased join hides
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* the joining relations, unless the column references are qualified.
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* Also, any unqualified column references are resolved to the Join RTE, if
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* there is a matching entry in the targetlist. But the way MERGE
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* execution is later setup, we expect all column references to resolve to
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* either the source or the target relation. Hence we must not add the
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* Join RTE to the namespace.
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*
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* The last entry must be for the top-level Join RTE. We don't want to
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* resolve any references to the Join RTE. So discard that.
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*
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* We also do not want to resolve any references from the leftside of the
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* Join since that corresponds to the target relation. References to the
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* columns of the target relation must be resolved from the result
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* relation and not the one that is used in the join. So the
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* mergeTarget_relation is marked invisible to both qualified as well as
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* unqualified references.
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*/
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Assert(list_length(namespace) > 1);
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namespace = list_truncate(namespace, list_length(namespace) - 1);
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pstate->p_namespace = list_concat(pstate->p_namespace, namespace);
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setNamespaceVisibilityForRTE(pstate->p_namespace,
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rt_fetch(mergeTarget_relation, pstate->p_rtable), false, false);
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/*
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* Expand the right relation and add its columns to the
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* mergeSourceTargetList. Note that the right relation can either be a
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* plain relation or a subquery or anything that can have a
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* RangeTableEntry.
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*/
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*mergeSourceTargetList = expandSourceTL(pstate, rt_rte, rt_rtindex);
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/*
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* Add a whole-row-Var entry to support references to "source.*".
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*/
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var = makeWholeRowVar(rt_rte, rt_rtindex, 0, false);
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te = makeTargetEntry((Expr *) var, list_length(*mergeSourceTargetList) + 1,
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NULL, true);
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*mergeSourceTargetList = lappend(*mergeSourceTargetList, te);
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return mergeTarget_relation;
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}
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/*
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* Make appropriate changes to the namespace visibility while transforming
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* individual action's quals and targetlist expressions. In particular, for
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* INSERT actions we must only see the source relation (since INSERT action is
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* invoked for NOT MATCHED tuples and hence there is no target tuple to deal
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* with). On the other hand, UPDATE and DELETE actions can see both source and
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* target relations.
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*
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* Also, since the internal Join node can hide the source and target
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* relations, we must explicitly make the respective relation as visible so
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* that columns can be referenced unqualified from these relations.
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*/
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static void
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setNamespaceForMergeAction(ParseState *pstate, MergeAction *action)
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{
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RangeTblEntry *targetRelRTE,
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*sourceRelRTE;
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/* Assume target relation is at index 1 */
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targetRelRTE = rt_fetch(1, pstate->p_rtable);
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/*
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* Assume that the top-level join RTE is at the end. The source relation
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* is just before that.
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*/
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sourceRelRTE = rt_fetch(list_length(pstate->p_rtable) - 1, pstate->p_rtable);
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switch (action->commandType)
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{
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case CMD_INSERT:
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/*
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* Inserts can't see target relation, but they can see source
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* relation.
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*/
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setNamespaceVisibilityForRTE(pstate->p_namespace,
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targetRelRTE, false, false);
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setNamespaceVisibilityForRTE(pstate->p_namespace,
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sourceRelRTE, true, true);
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break;
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case CMD_UPDATE:
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case CMD_DELETE:
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/*
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* Updates and deletes can see both target and source relations.
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*/
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setNamespaceVisibilityForRTE(pstate->p_namespace,
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targetRelRTE, true, true);
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setNamespaceVisibilityForRTE(pstate->p_namespace,
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sourceRelRTE, true, true);
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break;
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case CMD_NOTHING:
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break;
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default:
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elog(ERROR, "unknown action in MERGE WHEN clause");
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}
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}
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/*
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* transformMergeStmt -
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* transforms a MERGE statement
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*/
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Query *
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transformMergeStmt(ParseState *pstate, MergeStmt *stmt)
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{
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Query *qry = makeNode(Query);
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ListCell *l;
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AclMode targetPerms = ACL_NO_RIGHTS;
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bool is_terminal[2];
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JoinExpr *joinexpr;
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RangeTblEntry *resultRelRTE, *mergeRelRTE;
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/* There can't be any outer WITH to worry about */
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Assert(pstate->p_ctenamespace == NIL);
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qry->commandType = CMD_MERGE;
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/*
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* Check WHEN clauses for permissions and sanity
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*/
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is_terminal[0] = false;
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is_terminal[1] = false;
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foreach(l, stmt->mergeActionList)
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{
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MergeAction *action = (MergeAction *) lfirst(l);
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int when_type = (action->matched ? 0 : 1);
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/*
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* Collect action types so we can check Target permissions
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*/
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switch (action->commandType)
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{
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case CMD_INSERT:
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{
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InsertStmt *istmt = (InsertStmt *) action->stmt;
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SelectStmt *selectStmt = (SelectStmt *) istmt->selectStmt;
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/*
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* The grammar allows attaching ORDER BY, LIMIT, FOR
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* UPDATE, or WITH to a VALUES clause and also multiple
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* VALUES clauses. If we have any of those, ERROR.
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*/
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if (selectStmt && (selectStmt->valuesLists == NIL ||
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selectStmt->sortClause != NIL ||
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selectStmt->limitOffset != NULL ||
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selectStmt->limitCount != NULL ||
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selectStmt->lockingClause != NIL ||
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selectStmt->withClause != NULL))
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("SELECT not allowed in MERGE INSERT statement")));
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if (selectStmt && list_length(selectStmt->valuesLists) > 1)
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("Multiple VALUES clauses not allowed in MERGE INSERT statement")));
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targetPerms |= ACL_INSERT;
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}
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break;
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case CMD_UPDATE:
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targetPerms |= ACL_UPDATE;
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break;
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case CMD_DELETE:
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targetPerms |= ACL_DELETE;
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break;
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case CMD_NOTHING:
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break;
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default:
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elog(ERROR, "unknown action in MERGE WHEN clause");
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}
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/*
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* Check for unreachable WHEN clauses
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*/
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if (action->condition == NULL)
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is_terminal[when_type] = true;
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else if (is_terminal[when_type])
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("unreachable WHEN clause specified after unconditional WHEN clause")));
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}
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/*
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* Construct a query of the form
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* SELECT relation.ctid --junk attribute
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* ,relation.tableoid --junk attribute
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* ,source_relation.<somecols>
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* ,relation.<somecols>
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* FROM relation RIGHT JOIN source_relation
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* ON join_condition; -- no WHERE clause - all conditions are applied in
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* executor
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*
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* stmt->relation is the target relation, given as a RangeVar
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* stmt->source_relation is a RangeVar or subquery
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*
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* We specify the join as a RIGHT JOIN as a simple way of forcing the
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* first (larg) RTE to refer to the target table.
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*
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* The MERGE query's join can be tuned in some cases, see below for these
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* special case tweaks.
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*
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* We set QSRC_PARSER to show query constructed in parse analysis
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*
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* Note that we have only one Query for a MERGE statement and the planner
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* is called only once. That query is executed once to produce our stream
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* of candidate change rows, so the query must contain all of the columns
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* required by each of the targetlist or conditions for each action.
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*
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* As top-level statements INSERT, UPDATE and DELETE have a Query, whereas
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* with MERGE the individual actions do not require separate planning,
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* only different handling in the executor. See nodeModifyTable handling
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* of commandType CMD_MERGE.
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*
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* A sub-query can include the Target, but otherwise the sub-query cannot
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* reference the outermost Target table at all.
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*/
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qry->querySource = QSRC_PARSER;
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/*
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* Setup the target table. Unlike regular UPDATE/DELETE, we don't expand
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* inheritance for the target relation in case of MERGE.
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*
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* This special arrangement is required for handling partitioned tables
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* because we perform an JOIN between the target and the source relation to
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* identify the matching and not-matching rows. If we take the usual path
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* of expanding the target table's inheritance and create one subplan per
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* partition, then we we won't be able to correctly identify the matching
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* and not-matching rows since for a given source row, there may not be a
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* matching row in one partition, but it may exists in some other
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* partition. So we must first append all the qualifying rows from all the
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* partitions and then do the matching.
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*
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* Once a target row is returned by the underlying join, we find the
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* correct partition and setup required state to carry out UPDATE/DELETE.
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* All of this happens during execution.
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*/
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qry->resultRelation = setTargetTable(pstate, stmt->relation,
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false, /* do not expand inheritance */
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true, targetPerms);
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/*
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* Create a JOIN between the target and the source relation.
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*/
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joinexpr = makeNode(JoinExpr);
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joinexpr->isNatural = false;
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joinexpr->alias = NULL;
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joinexpr->usingClause = NIL;
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joinexpr->quals = stmt->join_condition;
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joinexpr->larg = (Node *) stmt->relation;
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joinexpr->rarg = (Node *) stmt->source_relation;
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/*
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* Simplify the MERGE query as much as possible
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*
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* These seem like things that could go into Optimizer, but they are
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* semantic simplifications rather than optimizations, per se.
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*
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* If there are no INSERT actions we won't be using the non-matching
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* candidate rows for anything, so no need for an outer join. We do still
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* need an inner join for UPDATE and DELETE actions.
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*/
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if (targetPerms & ACL_INSERT)
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joinexpr->jointype = JOIN_RIGHT;
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else
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joinexpr->jointype = JOIN_INNER;
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/*
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* We use a special purpose transformation here because the normal
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* routines don't quite work right for the MERGE case.
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*
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* A special mergeSourceTargetList is setup by transformMergeJoinClause().
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* It refers to all the attributes provided by the source relation. This
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* is later used by set_plan_refs() to fix the UPDATE/INSERT target lists
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* to so that they can correctly fetch the attributes from the source
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* relation.
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*
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* The target relation when used in the underlying join, gets a new RTE
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* with rte->inh set to true. We remember this RTE (and later pass on to
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* the planner and executor) for two main reasons:
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*
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* 1. If we ever need to run EvalPlanQual while performing MERGE, we must
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* make the modified tuple available to the underlying join query, which is
|
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* using a different RTE from the resultRelation RTE.
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*
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* 2. rewriteTargetListMerge() requires the RTE of the underlying join in
|
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* order to add junk CTID and TABLEOID attributes.
|
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*/
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qry->mergeTarget_relation = transformMergeJoinClause(pstate, (Node *) joinexpr,
|
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&qry->mergeSourceTargetList);
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/*
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* The target table referenced in the MERGE is looked up twice; once while
|
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* setting it up as the result relation and again when it's used in the
|
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* underlying the join query. In some rare situations, it may happen that
|
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* these lookups return different results, for example, if a new relation
|
||||
* with the same name gets created in a schema which is ahead in the
|
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* search_path, in between the two lookups.
|
||||
*
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||||
* It's a very narrow case, but nevertheless we guard against it by simply
|
||||
* checking if the OIDs returned by the two lookups is the same. If not, we
|
||||
* just throw an error.
|
||||
*/
|
||||
Assert(qry->resultRelation > 0);
|
||||
Assert(qry->mergeTarget_relation > 0);
|
||||
|
||||
/* Fetch both the RTEs */
|
||||
resultRelRTE = rt_fetch(qry->resultRelation, pstate->p_rtable);
|
||||
mergeRelRTE = rt_fetch(qry->mergeTarget_relation, pstate->p_rtable);
|
||||
|
||||
if (resultRelRTE->relid != mergeRelRTE->relid)
|
||||
ereport(ERROR,
|
||||
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
|
||||
errmsg("relation referenced by MERGE statement has changed")));
|
||||
|
||||
/*
|
||||
* This query should just provide the source relation columns. Later, in
|
||||
* preprocess_targetlist(), we shall also add "ctid" attribute of the
|
||||
* target relation to ensure that the target tuple can be fetched
|
||||
* correctly.
|
||||
*/
|
||||
qry->targetList = qry->mergeSourceTargetList;
|
||||
|
||||
/* qry has no WHERE clause so absent quals are shown as NULL */
|
||||
qry->jointree = makeFromExpr(pstate->p_joinlist, NULL);
|
||||
qry->rtable = pstate->p_rtable;
|
||||
|
||||
/*
|
||||
* XXX MERGE is unsupported in various cases
|
||||
*/
|
||||
if (!(pstate->p_target_relation->rd_rel->relkind == RELKIND_RELATION ||
|
||||
pstate->p_target_relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE))
|
||||
ereport(ERROR,
|
||||
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
|
||||
errmsg("MERGE is not supported for this relation type")));
|
||||
|
||||
if (pstate->p_target_relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE &&
|
||||
pstate->p_target_relation->rd_rel->relhassubclass)
|
||||
ereport(ERROR,
|
||||
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
|
||||
errmsg("MERGE is not supported for relations with inheritance")));
|
||||
|
||||
if (pstate->p_target_relation->rd_rel->relhasrules)
|
||||
ereport(ERROR,
|
||||
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
|
||||
errmsg("MERGE is not supported for relations with rules")));
|
||||
|
||||
/*
|
||||
* We now have a good query shape, so now look at the when conditions and
|
||||
* action targetlists.
|
||||
*
|
||||
* Overall, the MERGE Query's targetlist is NIL.
|
||||
*
|
||||
* Each individual action has its own targetlist that needs separate
|
||||
* transformation. These transforms don't do anything to the overall
|
||||
* targetlist, since that is only used for resjunk columns.
|
||||
*
|
||||
* We can reference any column in Target or Source, which is OK because
|
||||
* both of those already have RTEs. There is nothing like the EXCLUDED
|
||||
* pseudo-relation for INSERT ON CONFLICT.
|
||||
*/
|
||||
foreach(l, stmt->mergeActionList)
|
||||
{
|
||||
MergeAction *action = (MergeAction *) lfirst(l);
|
||||
|
||||
/*
|
||||
* Set namespace for the specific action. This must be done before
|
||||
* analyzing the WHEN quals and the action targetlisst.
|
||||
*/
|
||||
setNamespaceForMergeAction(pstate, action);
|
||||
|
||||
/*
|
||||
* Transform the when condition.
|
||||
*
|
||||
* Note that these quals are NOT added to the join quals; instead they
|
||||
* are evaluated separately during execution to decide which of the
|
||||
* WHEN MATCHED or WHEN NOT MATCHED actions to execute.
|
||||
*/
|
||||
action->qual = transformWhereClause(pstate, action->condition,
|
||||
EXPR_KIND_MERGE_WHEN_AND, "WHEN");
|
||||
|
||||
/*
|
||||
* Transform target lists for each INSERT and UPDATE action stmt
|
||||
*/
|
||||
switch (action->commandType)
|
||||
{
|
||||
case CMD_INSERT:
|
||||
{
|
||||
InsertStmt *istmt = (InsertStmt *) action->stmt;
|
||||
SelectStmt *selectStmt = (SelectStmt *) istmt->selectStmt;
|
||||
List *exprList = NIL;
|
||||
ListCell *lc;
|
||||
RangeTblEntry *rte;
|
||||
ListCell *icols;
|
||||
ListCell *attnos;
|
||||
List *icolumns;
|
||||
List *attrnos;
|
||||
|
||||
pstate->p_is_insert = true;
|
||||
|
||||
icolumns = checkInsertTargets(pstate, istmt->cols, &attrnos);
|
||||
Assert(list_length(icolumns) == list_length(attrnos));
|
||||
|
||||
/*
|
||||
* Handle INSERT much like in transformInsertStmt
|
||||
*/
|
||||
if (selectStmt == NULL)
|
||||
{
|
||||
/*
|
||||
* We have INSERT ... DEFAULT VALUES. We can handle
|
||||
* this case by emitting an empty targetlist --- all
|
||||
* columns will be defaulted when the planner expands
|
||||
* the targetlist.
|
||||
*/
|
||||
exprList = NIL;
|
||||
}
|
||||
else
|
||||
{
|
||||
/*
|
||||
* Process INSERT ... VALUES with a single VALUES
|
||||
* sublist. We treat this case separately for
|
||||
* efficiency. The sublist is just computed directly
|
||||
* as the Query's targetlist, with no VALUES RTE. So
|
||||
* it works just like a SELECT without any FROM.
|
||||
*/
|
||||
List *valuesLists = selectStmt->valuesLists;
|
||||
|
||||
Assert(list_length(valuesLists) == 1);
|
||||
Assert(selectStmt->intoClause == NULL);
|
||||
|
||||
/*
|
||||
* Do basic expression transformation (same as a ROW()
|
||||
* expr, but allow SetToDefault at top level)
|
||||
*/
|
||||
exprList = transformExpressionList(pstate,
|
||||
(List *) linitial(valuesLists),
|
||||
EXPR_KIND_VALUES_SINGLE,
|
||||
true);
|
||||
|
||||
/* Prepare row for assignment to target table */
|
||||
exprList = transformInsertRow(pstate, exprList,
|
||||
istmt->cols,
|
||||
icolumns, attrnos,
|
||||
false);
|
||||
}
|
||||
|
||||
/*
|
||||
* Generate action's target list using the computed list
|
||||
* of expressions. Also, mark all the target columns as
|
||||
* needing insert permissions.
|
||||
*/
|
||||
rte = pstate->p_target_rangetblentry;
|
||||
icols = list_head(icolumns);
|
||||
attnos = list_head(attrnos);
|
||||
foreach(lc, exprList)
|
||||
{
|
||||
Expr *expr = (Expr *) lfirst(lc);
|
||||
ResTarget *col;
|
||||
AttrNumber attr_num;
|
||||
TargetEntry *tle;
|
||||
|
||||
col = lfirst_node(ResTarget, icols);
|
||||
attr_num = (AttrNumber) lfirst_int(attnos);
|
||||
|
||||
tle = makeTargetEntry(expr,
|
||||
attr_num,
|
||||
col->name,
|
||||
false);
|
||||
action->targetList = lappend(action->targetList, tle);
|
||||
|
||||
rte->insertedCols = bms_add_member(rte->insertedCols,
|
||||
attr_num - FirstLowInvalidHeapAttributeNumber);
|
||||
|
||||
icols = lnext(icols);
|
||||
attnos = lnext(attnos);
|
||||
}
|
||||
}
|
||||
break;
|
||||
case CMD_UPDATE:
|
||||
{
|
||||
UpdateStmt *ustmt = (UpdateStmt *) action->stmt;
|
||||
|
||||
pstate->p_is_insert = false;
|
||||
action->targetList = transformUpdateTargetList(pstate, ustmt->targetList);
|
||||
}
|
||||
break;
|
||||
case CMD_DELETE:
|
||||
break;
|
||||
|
||||
case CMD_NOTHING:
|
||||
action->targetList = NIL;
|
||||
break;
|
||||
default:
|
||||
elog(ERROR, "unknown action in MERGE WHEN clause");
|
||||
}
|
||||
}
|
||||
|
||||
qry->mergeActionList = stmt->mergeActionList;
|
||||
|
||||
/* XXX maybe later */
|
||||
qry->returningList = NULL;
|
||||
|
||||
qry->hasTargetSRFs = false;
|
||||
qry->hasSubLinks = pstate->p_hasSubLinks;
|
||||
|
||||
assign_query_collations(pstate, qry);
|
||||
|
||||
return qry;
|
||||
}
|
||||
|
||||
static void
|
||||
setNamespaceVisibilityForRTE(List *namespace, RangeTblEntry *rte,
|
||||
bool rel_visible,
|
||||
bool cols_visible)
|
||||
{
|
||||
ListCell *lc;
|
||||
|
||||
foreach(lc, namespace)
|
||||
{
|
||||
ParseNamespaceItem *nsitem = (ParseNamespaceItem *) lfirst(lc);
|
||||
|
||||
if (nsitem->p_rte == rte)
|
||||
{
|
||||
nsitem->p_rel_visible = rel_visible;
|
||||
nsitem->p_cols_visible = cols_visible;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
}
|
||||
|
||||
/*
|
||||
* Expand the source relation to include all attributes of this RTE.
|
||||
*
|
||||
* This function is very similar to expandRelAttrs except that we don't mark
|
||||
* columns for SELECT privileges. That will be decided later when we transform
|
||||
* the action targetlists and the WHEN quals for actual references to the
|
||||
* source relation.
|
||||
*/
|
||||
static List *
|
||||
expandSourceTL(ParseState *pstate, RangeTblEntry *rte, int rtindex)
|
||||
{
|
||||
List *names,
|
||||
*vars;
|
||||
ListCell *name,
|
||||
*var;
|
||||
List *te_list = NIL;
|
||||
|
||||
expandRTE(rte, rtindex, 0, -1, false, &names, &vars);
|
||||
|
||||
/*
|
||||
* Require read access to the table.
|
||||
*/
|
||||
rte->requiredPerms |= ACL_SELECT;
|
||||
|
||||
forboth(name, names, var, vars)
|
||||
{
|
||||
char *label = strVal(lfirst(name));
|
||||
Var *varnode = (Var *) lfirst(var);
|
||||
TargetEntry *te;
|
||||
|
||||
te = makeTargetEntry((Expr *) varnode,
|
||||
(AttrNumber) pstate->p_next_resno++,
|
||||
label,
|
||||
false);
|
||||
te_list = lappend(te_list, te);
|
||||
}
|
||||
|
||||
Assert(name == NULL && var == NULL); /* lists not the same length? */
|
||||
|
||||
return te_list;
|
||||
}
|
||||
Reference in New Issue
Block a user