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953 lines
25 KiB
C
953 lines
25 KiB
C
/*-------------------------------------------------------------------------
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*
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* rewriteHandler.c
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* Primary module of query rewriter.
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*
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* Portions Copyright (c) 1996-2001, 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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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.95 2001/06/13 18:56:30 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/heapam.h"
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#include "catalog/pg_operator.h"
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#include "catalog/pg_type.h"
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#include "miscadmin.h"
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#include "nodes/makefuncs.h"
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#include "optimizer/clauses.h"
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#include "optimizer/prep.h"
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#include "optimizer/var.h"
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#include "parser/analyze.h"
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#include "parser/parse_expr.h"
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#include "parser/parse_oper.h"
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#include "parser/parse_target.h"
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#include "parser/parsetree.h"
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#include "parser/parse_type.h"
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#include "rewrite/rewriteHandler.h"
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#include "rewrite/rewriteManip.h"
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#include "utils/lsyscache.h"
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static Query *rewriteRuleAction(Query *parsetree,
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Query *rule_action,
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Node *rule_qual,
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int rt_index,
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CmdType event);
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static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index);
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static void markQueryForUpdate(Query *qry, bool skipOldNew);
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static List *matchLocks(CmdType event, RuleLock *rulelocks,
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int varno, Query *parsetree);
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static Query *fireRIRrules(Query *parsetree);
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/*
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* rewriteRuleAction -
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* Rewrite the rule action with appropriate qualifiers (taken from
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* the triggering query).
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*/
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static Query *
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rewriteRuleAction(Query *parsetree,
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Query *rule_action,
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Node *rule_qual,
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int rt_index,
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CmdType event)
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{
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int current_varno,
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new_varno;
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int rt_length;
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Query *sub_action;
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Query **sub_action_ptr;
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/*
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* Make modifiable copies of rule action and qual (what we're passed
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* are the stored versions in the relcache; don't touch 'em!).
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*/
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rule_action = (Query *) copyObject(rule_action);
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rule_qual = (Node *) copyObject(rule_qual);
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current_varno = rt_index;
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rt_length = length(parsetree->rtable);
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new_varno = PRS2_NEW_VARNO + rt_length;
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/*
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* Adjust rule action and qual to offset its varnos, so that we can
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* merge its rtable with the main parsetree's rtable.
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*
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* If the rule action is an INSERT...SELECT, the OLD/NEW rtable entries
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* will be in the SELECT part, and we have to modify that rather than
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* the top-level INSERT (kluge!).
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*/
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sub_action = getInsertSelectQuery(rule_action, &sub_action_ptr);
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OffsetVarNodes((Node *) sub_action, rt_length, 0);
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OffsetVarNodes(rule_qual, rt_length, 0);
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/* but references to *OLD* should point at original rt_index */
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ChangeVarNodes((Node *) sub_action,
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PRS2_OLD_VARNO + rt_length, rt_index, 0);
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ChangeVarNodes(rule_qual,
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PRS2_OLD_VARNO + rt_length, rt_index, 0);
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/*
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* Generate expanded rtable consisting of main parsetree's rtable
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* plus rule action's rtable; this becomes the complete rtable for the
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* rule action. Some of the entries may be unused after we finish
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* rewriting, but if we tried to clean those out we'd have a much harder
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* job to adjust RT indexes in the query's Vars. It's OK to have unused
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* RT entries, since planner will ignore them.
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*
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* NOTE: because planner will destructively alter rtable, we must ensure
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* that rule action's rtable is separate and shares no substructure with
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* the main rtable. Hence do a deep copy here.
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*/
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sub_action->rtable = nconc((List *) copyObject(parsetree->rtable),
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sub_action->rtable);
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/*
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* Each rule action's jointree should be the main parsetree's jointree
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* plus that rule's jointree, but usually *without* the original
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* rtindex that we're replacing (if present, which it won't be for
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* INSERT). Note that if the rule action refers to OLD, its jointree
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* will add a reference to rt_index. If the rule action doesn't refer
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* to OLD, but either the rule_qual or the user query quals do, then
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* we need to keep the original rtindex in the jointree to provide
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* data for the quals. We don't want the original rtindex to be
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* joined twice, however, so avoid keeping it if the rule action
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* mentions it.
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*
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* As above, the action's jointree must not share substructure with
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* the main parsetree's.
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*/
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if (sub_action->jointree != NULL)
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{
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bool keeporig;
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List *newjointree;
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keeporig = (!rangeTableEntry_used((Node *) sub_action->jointree,
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rt_index, 0)) &&
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(rangeTableEntry_used(rule_qual, rt_index, 0) ||
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rangeTableEntry_used(parsetree->jointree->quals, rt_index, 0));
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newjointree = adjustJoinTreeList(parsetree, !keeporig, rt_index);
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sub_action->jointree->fromlist =
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nconc(newjointree, sub_action->jointree->fromlist);
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}
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/*
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* We copy the qualifications of the parsetree to the action and vice
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* versa. So force hasSubLinks if one of them has it. If this is not
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* right, the flag will get cleared later, but we mustn't risk having
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* it not set when it needs to be. (XXX this should probably be handled
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* by AddQual and friends, not here...)
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*/
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if (parsetree->hasSubLinks)
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sub_action->hasSubLinks = TRUE;
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else if (sub_action->hasSubLinks)
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parsetree->hasSubLinks = TRUE;
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/*
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* Event Qualification forces copying of parsetree and splitting into
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* two queries one w/rule_qual, one w/NOT rule_qual. Also add user
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* query qual onto rule action
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*/
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AddQual(sub_action, rule_qual);
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AddQual(sub_action, parsetree->jointree->quals);
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/*
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* Rewrite new.attribute w/ right hand side of target-list entry for
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* appropriate field name in insert/update.
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*
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* KLUGE ALERT: since ResolveNew returns a mutated copy, we can't just
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* apply it to sub_action; we have to remember to update the sublink
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* inside rule_action, too.
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*/
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if (event == CMD_INSERT || event == CMD_UPDATE)
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{
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sub_action = (Query *) ResolveNew((Node *) sub_action,
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new_varno,
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0,
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parsetree->targetList,
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event,
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current_varno);
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if (sub_action_ptr)
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*sub_action_ptr = sub_action;
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else
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rule_action = sub_action;
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}
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return rule_action;
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}
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/*
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* Copy the query's jointree list, and optionally attempt to remove any
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* occurrence of the given rt_index as a top-level join item (we do not look
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* for it within join items; this is OK because we are only expecting to find
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* it as an UPDATE or DELETE target relation, which will be at the top level
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* of the join). Returns modified jointree list --- this is a separate copy
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* sharing no nodes with the original.
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*/
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static List *
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adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
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{
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List *newjointree = copyObject(parsetree->jointree->fromlist);
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List *jjt;
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if (removert)
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{
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foreach(jjt, newjointree)
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{
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RangeTblRef *rtr = lfirst(jjt);
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if (IsA(rtr, RangeTblRef) &&rtr->rtindex == rt_index)
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{
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newjointree = lremove(rtr, newjointree);
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break;
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}
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}
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}
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return newjointree;
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}
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/*
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* matchLocks -
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* match the list of locks and returns the matching rules
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*/
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static List *
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matchLocks(CmdType event,
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RuleLock *rulelocks,
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int varno,
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Query *parsetree)
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{
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List *real_locks = NIL;
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int nlocks;
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int i;
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Assert(rulelocks != NULL); /* we get called iff there is some lock */
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Assert(parsetree != NULL);
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if (parsetree->commandType != CMD_SELECT)
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{
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if (parsetree->resultRelation != varno)
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return NIL;
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}
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nlocks = rulelocks->numLocks;
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for (i = 0; i < nlocks; i++)
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{
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RewriteRule *oneLock = rulelocks->rules[i];
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if (oneLock->event == event)
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{
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if (parsetree->commandType != CMD_SELECT ||
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(oneLock->attrno == -1 ?
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rangeTableEntry_used((Node *) parsetree, varno, 0) :
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attribute_used((Node *) parsetree,
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varno, oneLock->attrno, 0)))
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real_locks = lappend(real_locks, oneLock);
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}
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}
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return real_locks;
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}
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static Query *
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ApplyRetrieveRule(Query *parsetree,
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RewriteRule *rule,
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int rt_index,
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bool relation_level,
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Relation relation,
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bool relIsUsed)
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{
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Query *rule_action;
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RangeTblEntry *rte,
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*subrte;
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if (length(rule->actions) != 1)
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elog(ERROR, "ApplyRetrieveRule: expected just one rule action");
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if (rule->qual != NULL)
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elog(ERROR, "ApplyRetrieveRule: can't handle qualified ON SELECT rule");
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if (!relation_level)
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elog(ERROR, "ApplyRetrieveRule: can't handle per-attribute ON SELECT rule");
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/*
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* Make a modifiable copy of the view query, and recursively expand
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* any view references inside it.
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*/
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rule_action = copyObject(lfirst(rule->actions));
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rule_action = fireRIRrules(rule_action);
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/*
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* VIEWs are really easy --- just plug the view query in as a
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* subselect, replacing the relation's original RTE.
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*/
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rte = rt_fetch(rt_index, parsetree->rtable);
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rte->relname = NULL;
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rte->relid = InvalidOid;
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rte->subquery = rule_action;
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rte->inh = false; /* must not be set for a subquery */
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/*
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* We move the view's permission check data down to its rangetable.
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* The checks will actually be done against the *OLD* entry therein.
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*/
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subrte = rt_fetch(PRS2_OLD_VARNO, rule_action->rtable);
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Assert(subrte->relid == relation->rd_id);
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subrte->checkForRead = rte->checkForRead;
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subrte->checkForWrite = rte->checkForWrite;
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subrte->checkAsUser = rte->checkAsUser;
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rte->checkForRead = false; /* no permission check on subquery itself */
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rte->checkForWrite = false;
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rte->checkAsUser = InvalidOid;
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/*
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* FOR UPDATE of view?
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*/
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if (intMember(rt_index, parsetree->rowMarks))
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{
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/*
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* Remove the view from the list of rels that will actually be
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* marked FOR UPDATE by the executor. It will still be access-
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* checked for write access, though.
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*/
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parsetree->rowMarks = lremovei(rt_index, parsetree->rowMarks);
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/*
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* Set up the view's referenced tables as if FOR UPDATE.
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*/
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markQueryForUpdate(rule_action, true);
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}
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return parsetree;
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}
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/*
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* Recursively mark all relations used by a view as FOR UPDATE.
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*
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* This may generate an invalid query, eg if some sub-query uses an
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* aggregate. We leave it to the planner to detect that.
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*
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* NB: this must agree with the parser's transformForUpdate() routine.
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*/
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static void
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markQueryForUpdate(Query *qry, bool skipOldNew)
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{
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Index rti = 0;
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List *l;
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foreach(l, qry->rtable)
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{
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RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
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rti++;
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/* Ignore OLD and NEW entries if we are at top level of view */
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if (skipOldNew &&
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(rti == PRS2_OLD_VARNO || rti == PRS2_NEW_VARNO))
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continue;
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if (rte->subquery)
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{
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/* FOR UPDATE of subquery is propagated to subquery's rels */
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markQueryForUpdate(rte->subquery, false);
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}
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else
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{
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if (!intMember(rti, qry->rowMarks))
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qry->rowMarks = lappendi(qry->rowMarks, rti);
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rte->checkForWrite = true;
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}
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}
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}
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/*
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* fireRIRonSubLink -
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* Apply fireRIRrules() to each SubLink (subselect in expression) found
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* in the given tree.
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*
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* NOTE: although this has the form of a walker, we cheat and modify the
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* SubLink nodes in-place. It is caller's responsibility to ensure that
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* no unwanted side-effects occur!
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*
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* This is unlike most of the other routines that recurse into subselects,
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* because we must take control at the SubLink node in order to replace
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* the SubLink's subselect link with the possibly-rewritten subquery.
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*/
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static bool
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fireRIRonSubLink(Node *node, void *context)
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{
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if (node == NULL)
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return false;
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if (IsA(node, SubLink))
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{
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SubLink *sub = (SubLink *) node;
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/* Do what we came for */
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sub->subselect = (Node *) fireRIRrules((Query *) (sub->subselect));
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/* Fall through to process lefthand args of SubLink */
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}
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/*
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* Do NOT recurse into Query nodes, because fireRIRrules already
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* processed subselects of subselects for us.
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*/
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return expression_tree_walker(node, fireRIRonSubLink,
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(void *) context);
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}
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/*
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* fireRIRrules -
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* Apply all RIR rules on each rangetable entry in a query
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*/
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static Query *
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fireRIRrules(Query *parsetree)
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{
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int rt_index;
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/*
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* don't try to convert this into a foreach loop, because rtable list
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* can get changed each time through...
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*/
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rt_index = 0;
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while (rt_index < length(parsetree->rtable))
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{
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RangeTblEntry *rte;
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Relation rel;
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List *locks;
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RuleLock *rules;
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RewriteRule *rule;
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LOCKMODE lockmode;
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bool relIsUsed;
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int i;
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List *l;
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++rt_index;
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rte = rt_fetch(rt_index, parsetree->rtable);
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/*
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* A subquery RTE can't have associated rules, so there's nothing
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* to do to this level of the query, but we must recurse into the
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* subquery to expand any rule references in it.
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*/
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if (rte->subquery)
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{
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rte->subquery = fireRIRrules(rte->subquery);
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continue;
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}
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/*
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* If the table is not referenced in the query, then we ignore it.
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* This prevents infinite expansion loop due to new rtable entries
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* inserted by expansion of a rule. A table is referenced if it is
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* part of the join set (a source table), or is referenced by any
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* Var nodes, or is the result table.
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*/
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relIsUsed = rangeTableEntry_used((Node *) parsetree, rt_index, 0);
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if (!relIsUsed && rt_index != parsetree->resultRelation)
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continue;
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/*
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* This may well be the first access to the relation during the
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* current statement (it will be, if this Query was extracted from
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* a rule or somehow got here other than via the parser).
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* Therefore, grab the appropriate lock type for the relation, and
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* do not release it until end of transaction. This protects the
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* rewriter and planner against schema changes mid-query.
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*
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* If the relation is the query's result relation, then
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* RewriteQuery() already got the right lock on it, so we need no
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* additional lock. Otherwise, check to see if the relation is
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* accessed FOR UPDATE or not.
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*/
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if (rt_index == parsetree->resultRelation)
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lockmode = NoLock;
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else if (intMember(rt_index, parsetree->rowMarks))
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lockmode = RowShareLock;
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else
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lockmode = AccessShareLock;
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rel = heap_openr(rte->relname, lockmode);
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/*
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* Check to see if relation's OID matches the RTE. If not, the RTE
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* actually refers to an older relation that had the same name.
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* Eventually we might want to reparse the referencing rule, but
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* for now all we can do is punt.
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*/
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if (RelationGetRelid(rel) != rte->relid)
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elog(ERROR, "Relation \"%s\" with OID %u no longer exists",
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rte->relname, rte->relid);
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/*
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* Collect the RIR rules that we must apply
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*/
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rules = rel->rd_rules;
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if (rules == NULL)
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{
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heap_close(rel, NoLock);
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continue;
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}
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locks = NIL;
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for (i = 0; i < rules->numLocks; i++)
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{
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rule = rules->rules[i];
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if (rule->event != CMD_SELECT)
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continue;
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if (rule->attrno > 0)
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{
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/* per-attr rule; do we need it? */
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if (!attribute_used((Node *) parsetree, rt_index,
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rule->attrno, 0))
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continue;
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}
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locks = lappend(locks, rule);
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}
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/*
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* Now apply them
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*/
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foreach(l, locks)
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{
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rule = lfirst(l);
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|
|
parsetree = ApplyRetrieveRule(parsetree,
|
|
rule,
|
|
rt_index,
|
|
rule->attrno == -1,
|
|
rel,
|
|
relIsUsed);
|
|
}
|
|
|
|
heap_close(rel, NoLock);
|
|
}
|
|
|
|
/*
|
|
* Recurse into sublink subqueries, too.
|
|
*/
|
|
if (parsetree->hasSubLinks)
|
|
query_tree_walker(parsetree, fireRIRonSubLink, NULL,
|
|
false /* already handled the ones in rtable */ );
|
|
|
|
/*
|
|
* If the query was marked having aggregates, check if this is still
|
|
* true after rewriting. Ditto for sublinks. Note there should be no
|
|
* aggs in the qual at this point. (Does this code still do anything
|
|
* useful? The view-becomes-subselect-in-FROM approach doesn't look
|
|
* like it could remove aggs or sublinks...)
|
|
*/
|
|
if (parsetree->hasAggs)
|
|
{
|
|
parsetree->hasAggs = checkExprHasAggs((Node *) parsetree);
|
|
if (parsetree->hasAggs)
|
|
if (checkExprHasAggs((Node *) parsetree->jointree))
|
|
elog(ERROR, "fireRIRrules: failed to remove aggs from qual");
|
|
}
|
|
if (parsetree->hasSubLinks)
|
|
parsetree->hasSubLinks = checkExprHasSubLink((Node *) parsetree);
|
|
|
|
return parsetree;
|
|
}
|
|
|
|
|
|
/*
|
|
* idea is to fire regular rules first, then qualified instead
|
|
* rules and unqualified instead rules last. Any lemming is counted for.
|
|
*/
|
|
static List *
|
|
orderRules(List *locks)
|
|
{
|
|
List *regular = NIL;
|
|
List *instead_rules = NIL;
|
|
List *instead_qualified = NIL;
|
|
List *i;
|
|
|
|
foreach(i, locks)
|
|
{
|
|
RewriteRule *rule_lock = (RewriteRule *) lfirst(i);
|
|
|
|
if (rule_lock->isInstead)
|
|
{
|
|
if (rule_lock->qual == NULL)
|
|
instead_rules = lappend(instead_rules, rule_lock);
|
|
else
|
|
instead_qualified = lappend(instead_qualified, rule_lock);
|
|
}
|
|
else
|
|
regular = lappend(regular, rule_lock);
|
|
}
|
|
return nconc(nconc(regular, instead_qualified), instead_rules);
|
|
}
|
|
|
|
|
|
/*
|
|
* Modify the given query by adding 'AND NOT rule_qual' to its qualification.
|
|
* This is used to generate suitable "else clauses" for conditional INSTEAD
|
|
* rules.
|
|
*
|
|
* The rule_qual may contain references to OLD or NEW. OLD references are
|
|
* replaced by references to the specified rt_index (the relation that the
|
|
* rule applies to). NEW references are only possible for INSERT and UPDATE
|
|
* queries on the relation itself, and so they should be replaced by copies
|
|
* of the related entries in the query's own targetlist.
|
|
*/
|
|
static Query *
|
|
CopyAndAddQual(Query *parsetree,
|
|
Node *rule_qual,
|
|
int rt_index,
|
|
CmdType event)
|
|
{
|
|
Query *new_tree = (Query *) copyObject(parsetree);
|
|
Node *new_qual = (Node *) copyObject(rule_qual);
|
|
|
|
/* Fix references to OLD */
|
|
ChangeVarNodes(new_qual, PRS2_OLD_VARNO, rt_index, 0);
|
|
/* Fix references to NEW */
|
|
if (event == CMD_INSERT || event == CMD_UPDATE)
|
|
new_qual = ResolveNew(new_qual,
|
|
PRS2_NEW_VARNO,
|
|
0,
|
|
parsetree->targetList,
|
|
event,
|
|
rt_index);
|
|
/* And attach the fixed qual */
|
|
AddNotQual(new_tree, new_qual);
|
|
|
|
return new_tree;
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
* fireRules -
|
|
* Iterate through rule locks applying rules.
|
|
* All rules create their own parsetrees. Instead rules
|
|
* with rule qualification save the original parsetree
|
|
* and add their negated qualification to it. Real instead
|
|
* rules finally throw away the original parsetree.
|
|
*
|
|
* remember: reality is for dead birds -- glass
|
|
*
|
|
*/
|
|
static List *
|
|
fireRules(Query *parsetree,
|
|
int rt_index,
|
|
CmdType event,
|
|
bool *instead_flag,
|
|
List *locks,
|
|
List **qual_products)
|
|
{
|
|
List *results = NIL;
|
|
List *i;
|
|
|
|
/* choose rule to fire from list of rules */
|
|
if (locks == NIL)
|
|
return NIL;
|
|
|
|
locks = orderRules(locks); /* real instead rules last */
|
|
|
|
foreach(i, locks)
|
|
{
|
|
RewriteRule *rule_lock = (RewriteRule *) lfirst(i);
|
|
Node *event_qual;
|
|
List *actions;
|
|
List *r;
|
|
|
|
/* multiple rule action time */
|
|
*instead_flag = rule_lock->isInstead;
|
|
event_qual = rule_lock->qual;
|
|
actions = rule_lock->actions;
|
|
|
|
if (event_qual != NULL && *instead_flag)
|
|
{
|
|
Query *qual_product;
|
|
|
|
/*
|
|
* If there are instead rules with qualifications, the
|
|
* original query is still performed. But all the negated rule
|
|
* qualifications of the instead rules are added so it does
|
|
* its actions only in cases where the rule quals of all
|
|
* instead rules are false. Think of it as the default action
|
|
* in a case. We save this in *qual_products so
|
|
* deepRewriteQuery() can add it to the query list after we
|
|
* mangled it up enough.
|
|
*/
|
|
if (*qual_products == NIL)
|
|
qual_product = parsetree;
|
|
else
|
|
qual_product = (Query *) lfirst(*qual_products);
|
|
|
|
qual_product = CopyAndAddQual(qual_product,
|
|
event_qual,
|
|
rt_index,
|
|
event);
|
|
|
|
*qual_products = makeList1(qual_product);
|
|
}
|
|
|
|
foreach(r, actions)
|
|
{
|
|
Query *rule_action = lfirst(r);
|
|
|
|
if (rule_action->commandType == CMD_NOTHING)
|
|
continue;
|
|
|
|
rule_action = rewriteRuleAction(parsetree, rule_action,
|
|
event_qual, rt_index, event);
|
|
|
|
results = lappend(results, rule_action);
|
|
}
|
|
|
|
/*
|
|
* If this was an unqualified instead rule, throw away an
|
|
* eventually saved 'default' parsetree
|
|
*/
|
|
if (event_qual == NULL && *instead_flag)
|
|
*qual_products = NIL;
|
|
}
|
|
return results;
|
|
}
|
|
|
|
|
|
|
|
static List *
|
|
RewriteQuery(Query *parsetree, bool *instead_flag, List **qual_products)
|
|
{
|
|
CmdType event;
|
|
List *product_queries = NIL;
|
|
int result_relation;
|
|
RangeTblEntry *rt_entry;
|
|
Relation rt_entry_relation;
|
|
RuleLock *rt_entry_locks;
|
|
|
|
Assert(parsetree != NULL);
|
|
|
|
event = parsetree->commandType;
|
|
|
|
/*
|
|
* SELECT rules are handled later when we have all the queries that
|
|
* should get executed
|
|
*/
|
|
if (event == CMD_SELECT)
|
|
return NIL;
|
|
|
|
/*
|
|
* Utilities aren't rewritten at all - why is this here?
|
|
*/
|
|
if (event == CMD_UTILITY)
|
|
return NIL;
|
|
|
|
/*
|
|
* the statement is an update, insert or delete - fire rules on it.
|
|
*/
|
|
result_relation = parsetree->resultRelation;
|
|
Assert(result_relation != 0);
|
|
rt_entry = rt_fetch(result_relation, parsetree->rtable);
|
|
|
|
/*
|
|
* This may well be the first access to the result relation during the
|
|
* current statement (it will be, if this Query was extracted from a
|
|
* rule or somehow got here other than via the parser). Therefore,
|
|
* grab the appropriate lock type for a result relation, and do not
|
|
* release it until end of transaction. This protects the rewriter
|
|
* and planner against schema changes mid-query.
|
|
*/
|
|
rt_entry_relation = heap_openr(rt_entry->relname, RowExclusiveLock);
|
|
|
|
/*
|
|
* Check to see if relation's OID matches the RTE. If not, the RTE
|
|
* actually refers to an older relation that had the same name.
|
|
* Eventually we might want to reparse the referencing rule, but
|
|
* for now all we can do is punt.
|
|
*/
|
|
if (RelationGetRelid(rt_entry_relation) != rt_entry->relid)
|
|
elog(ERROR, "Relation \"%s\" with OID %u no longer exists",
|
|
rt_entry->relname, rt_entry->relid);
|
|
|
|
/*
|
|
* Collect and apply the appropriate rules.
|
|
*/
|
|
rt_entry_locks = rt_entry_relation->rd_rules;
|
|
|
|
if (rt_entry_locks != NULL)
|
|
{
|
|
List *locks = matchLocks(event, rt_entry_locks,
|
|
result_relation, parsetree);
|
|
|
|
product_queries = fireRules(parsetree,
|
|
result_relation,
|
|
event,
|
|
instead_flag,
|
|
locks,
|
|
qual_products);
|
|
}
|
|
|
|
heap_close(rt_entry_relation, NoLock); /* keep lock! */
|
|
|
|
return product_queries;
|
|
}
|
|
|
|
|
|
/*
|
|
* to avoid infinite recursion, we restrict the number of times a query
|
|
* can be rewritten. Detecting cycles is left for the reader as an exercise.
|
|
*/
|
|
#ifndef REWRITE_INVOKE_MAX
|
|
#define REWRITE_INVOKE_MAX 10
|
|
#endif
|
|
|
|
static int numQueryRewriteInvoked = 0;
|
|
|
|
/*
|
|
* deepRewriteQuery -
|
|
* rewrites the query and apply the rules again on the queries rewritten
|
|
*/
|
|
static List *
|
|
deepRewriteQuery(Query *parsetree)
|
|
{
|
|
List *n;
|
|
List *rewritten = NIL;
|
|
List *result;
|
|
bool instead;
|
|
List *qual_products = NIL;
|
|
|
|
if (++numQueryRewriteInvoked > REWRITE_INVOKE_MAX)
|
|
{
|
|
elog(ERROR, "query rewritten %d times, may contain cycles",
|
|
numQueryRewriteInvoked - 1);
|
|
}
|
|
|
|
instead = FALSE;
|
|
result = RewriteQuery(parsetree, &instead, &qual_products);
|
|
|
|
foreach(n, result)
|
|
{
|
|
Query *pt = lfirst(n);
|
|
List *newstuff;
|
|
|
|
newstuff = deepRewriteQuery(pt);
|
|
if (newstuff != NIL)
|
|
rewritten = nconc(rewritten, newstuff);
|
|
}
|
|
|
|
/*
|
|
* qual_products are the original query with the negated rule
|
|
* qualification of an instead rule
|
|
*/
|
|
if (qual_products != NIL)
|
|
rewritten = nconc(rewritten, qual_products);
|
|
|
|
/*
|
|
* The original query is appended last (if no "instead" rule) because
|
|
* update and delete rule actions might not do anything if they are
|
|
* invoked after the update or delete is performed. The command
|
|
* counter increment between the query execution makes the deleted
|
|
* (and maybe the updated) tuples disappear so the scans for them in
|
|
* the rule actions cannot find them.
|
|
*/
|
|
if (!instead)
|
|
rewritten = lappend(rewritten, parsetree);
|
|
|
|
return rewritten;
|
|
}
|
|
|
|
|
|
/*
|
|
* QueryRewriteOne -
|
|
* rewrite one query
|
|
*/
|
|
static List *
|
|
QueryRewriteOne(Query *parsetree)
|
|
{
|
|
numQueryRewriteInvoked = 0;
|
|
|
|
/*
|
|
* take a deep breath and apply all the rewrite rules - ay
|
|
*/
|
|
return deepRewriteQuery(parsetree);
|
|
}
|
|
|
|
|
|
/*
|
|
* QueryRewrite -
|
|
* Primary entry point to the query rewriter.
|
|
* Rewrite one query via query rewrite system, possibly returning 0
|
|
* or many queries.
|
|
*
|
|
* NOTE: The code in QueryRewrite was formerly in pg_parse_and_plan(), and was
|
|
* moved here so that it would be invoked during EXPLAIN.
|
|
*/
|
|
List *
|
|
QueryRewrite(Query *parsetree)
|
|
{
|
|
List *querylist;
|
|
List *results = NIL;
|
|
List *l;
|
|
|
|
/*
|
|
* Step 1
|
|
*
|
|
* Apply all non-SELECT rules possibly getting 0 or many queries
|
|
*/
|
|
querylist = QueryRewriteOne(parsetree);
|
|
|
|
/*
|
|
* Step 2
|
|
*
|
|
* Apply all the RIR rules on each query
|
|
*/
|
|
foreach(l, querylist)
|
|
{
|
|
Query *query = (Query *) lfirst(l);
|
|
|
|
query = fireRIRrules(query);
|
|
|
|
/*
|
|
* If the query target was rewritten as a view, complain.
|
|
*/
|
|
if (query->resultRelation)
|
|
{
|
|
RangeTblEntry *rte = rt_fetch(query->resultRelation,
|
|
query->rtable);
|
|
|
|
if (rte->subquery)
|
|
{
|
|
switch (query->commandType)
|
|
{
|
|
case CMD_INSERT:
|
|
elog(ERROR, "Cannot insert into a view without an appropriate rule");
|
|
break;
|
|
case CMD_UPDATE:
|
|
elog(ERROR, "Cannot update a view without an appropriate rule");
|
|
break;
|
|
case CMD_DELETE:
|
|
elog(ERROR, "Cannot delete from a view without an appropriate rule");
|
|
break;
|
|
default:
|
|
elog(ERROR, "QueryRewrite: unexpected commandType %d",
|
|
(int) query->commandType);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
results = lappend(results, query);
|
|
}
|
|
|
|
return results;
|
|
}
|