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673 lines
16 KiB
C
673 lines
16 KiB
C
/*-------------------------------------------------------------------------
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*
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* rewriteHandler.c--
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*
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* 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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* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.9 1998/01/07 21:04:37 momjian 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 "miscadmin.h"
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#include "utils/palloc.h"
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#include "utils/elog.h"
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#include "utils/rel.h"
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#include "nodes/pg_list.h"
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#include "nodes/primnodes.h"
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#include "parser/parsetree.h" /* for parsetree manipulation */
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#include "nodes/parsenodes.h"
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#include "rewrite/rewriteSupport.h"
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#include "rewrite/rewriteHandler.h"
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#include "rewrite/rewriteManip.h"
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#include "rewrite/locks.h"
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#include "commands/creatinh.h"
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#include "access/heapam.h"
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static void
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ApplyRetrieveRule(Query *parsetree, RewriteRule *rule,
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int rt_index, int relation_level, int *modified);
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static List *
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fireRules(Query *parsetree, int rt_index, CmdType event,
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bool *instead_flag, List *locks, List **qual_products);
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static List *deepRewriteQuery(Query *parsetree);
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/*
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* gatherRewriteMeta -
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* Gather meta information about parsetree, and rule. Fix rule body
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* and qualifier so that they can be mixed with the parsetree and
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* maintain semantic validity
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*/
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static RewriteInfo *
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gatherRewriteMeta(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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bool *instead_flag)
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{
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RewriteInfo *info;
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int rt_length;
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int result_reln;
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info = (RewriteInfo *) palloc(sizeof(RewriteInfo));
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info->rt_index = rt_index;
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info->event = event;
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info->instead_flag = *instead_flag;
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info->rule_action = (Query *) copyObject(rule_action);
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info->rule_qual = (Node *) copyObject(rule_qual);
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if (info->rule_action == NULL)
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info->nothing = TRUE;
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else
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{
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info->nothing = FALSE;
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info->action = info->rule_action->commandType;
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info->current_varno = rt_index;
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info->rt = parsetree->rtable;
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rt_length = length(info->rt);
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info->rt = append(info->rt, info->rule_action->rtable);
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info->new_varno = PRS2_NEW_VARNO + rt_length;
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OffsetVarNodes(info->rule_action->qual, rt_length);
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OffsetVarNodes((Node *) info->rule_action->targetList, rt_length);
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OffsetVarNodes(info->rule_qual, rt_length);
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ChangeVarNodes((Node *) info->rule_action->qual,
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PRS2_CURRENT_VARNO + rt_length, rt_index);
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ChangeVarNodes((Node *) info->rule_action->targetList,
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PRS2_CURRENT_VARNO + rt_length, rt_index);
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ChangeVarNodes(info->rule_qual,
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PRS2_CURRENT_VARNO + rt_length, rt_index);
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/*
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* bug here about replace CURRENT -- sort of replace current is
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* deprecated now so this code shouldn't really need to be so
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* clutzy but.....
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*/
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if (info->action != CMD_SELECT)
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{ /* i.e update XXXXX */
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int new_result_reln = 0;
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result_reln = info->rule_action->resultRelation;
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switch (result_reln)
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{
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case PRS2_CURRENT_VARNO:
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new_result_reln = rt_index;
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break;
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case PRS2_NEW_VARNO: /* XXX */
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default:
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new_result_reln = result_reln + rt_length;
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break;
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}
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info->rule_action->resultRelation = new_result_reln;
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}
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}
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return info;
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}
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static List *
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OptimizeRIRRules(List *locks)
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{
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List *attr_level = NIL,
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*i;
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List *relation_level = NIL;
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foreach(i, locks)
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{
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RewriteRule *rule_lock = lfirst(i);
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if (rule_lock->attrno == -1)
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relation_level = lappend(relation_level, rule_lock);
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else
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attr_level = lappend(attr_level, rule_lock);
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}
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return nconc(relation_level, attr_level);
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}
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/*
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* idea is to put instead rules before regular rules so that
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* excess semantically queasy queries aren't processed
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*/
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static List *
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orderRules(List *locks)
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{
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List *regular = NIL,
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*i;
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List *instead_rules = NIL;
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foreach(i, locks)
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{
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RewriteRule *rule_lock = (RewriteRule *) lfirst(i);
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if (rule_lock->isInstead)
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instead_rules = lappend(instead_rules, rule_lock);
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else
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regular = lappend(regular, rule_lock);
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}
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return nconc(regular, instead_rules);
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}
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static int
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AllRetrieve(List *actions)
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{
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List *n;
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foreach(n, actions)
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{
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Query *pt = lfirst(n);
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/*
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* in the old postgres code, we check whether command_type is a
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* consp of '('*'.commandType). but we've never supported
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* transitive closures. Hence removed - ay 10/94.
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*/
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if (pt->commandType != CMD_SELECT)
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return false;
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}
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return true;
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}
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static List *
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FireRetrieveRulesAtQuery(Query *parsetree,
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int rt_index,
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Relation relation,
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bool *instead_flag,
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int rule_flag)
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{
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List *i,
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*locks;
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RuleLock *rt_entry_locks = NULL;
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List *work = NIL;
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if ((rt_entry_locks = relation->rd_rules) == NULL)
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return NIL;
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locks = matchLocks(CMD_SELECT, rt_entry_locks, rt_index, parsetree);
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/* find all retrieve instead */
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foreach(i, locks)
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{
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RewriteRule *rule_lock = (RewriteRule *) lfirst(i);
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if (!rule_lock->isInstead)
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continue;
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work = lappend(work, rule_lock);
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}
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if (work != NIL)
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{
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work = OptimizeRIRRules(locks);
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foreach(i, work)
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{
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RewriteRule *rule_lock = lfirst(i);
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int relation_level;
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int modified = FALSE;
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relation_level = (rule_lock->attrno == -1);
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if (rule_lock->actions == NIL)
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{
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*instead_flag = TRUE;
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return NIL;
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}
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if (!rule_flag &&
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length(rule_lock->actions) >= 2 &&
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AllRetrieve(rule_lock->actions))
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{
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*instead_flag = TRUE;
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return rule_lock->actions;
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}
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ApplyRetrieveRule(parsetree, rule_lock, rt_index, relation_level,
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&modified);
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if (modified)
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{
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*instead_flag = TRUE;
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FixResdomTypes(parsetree->targetList);
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return lcons(parsetree, NIL);
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}
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}
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}
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return NIL;
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}
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/* Idea is like this:
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*
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* retrieve-instead-retrieve rules have different semantics than update nodes
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* Separate RIR rules from others. Pass others to FireRules.
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* Order RIR rules and process.
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*
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* side effect: parsetree's rtable field might be changed
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*/
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static void
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ApplyRetrieveRule(Query *parsetree,
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RewriteRule *rule,
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int rt_index,
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int relation_level,
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int *modified)
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{
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Query *rule_action = NULL;
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Node *rule_qual;
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List *rtable,
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*rt;
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int nothing,
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rt_length;
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int badsql = FALSE;
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rule_qual = rule->qual;
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if (rule->actions)
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{
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if (length(rule->actions) > 1) /* ??? because we don't handle
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* rules with more than one
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* action? -ay */
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return;
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rule_action = copyObject(lfirst(rule->actions));
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nothing = FALSE;
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}
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else
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{
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nothing = TRUE;
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}
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rtable = copyObject(parsetree->rtable);
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foreach(rt, rtable)
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{
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RangeTblEntry *rte = lfirst(rt);
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/*
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* this is to prevent add_missing_vars_to_base_rels() from adding
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* a bogus entry to the new target list.
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*/
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rte->inFromCl = false;
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}
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rt_length = length(rtable);
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rtable = nconc(rtable, copyObject(rule_action->rtable));
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parsetree->rtable = rtable;
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rule_action->rtable = rtable;
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OffsetVarNodes(rule_action->qual, rt_length);
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OffsetVarNodes((Node *) rule_action->targetList, rt_length);
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OffsetVarNodes(rule_qual, rt_length);
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ChangeVarNodes(rule_action->qual,
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PRS2_CURRENT_VARNO + rt_length, rt_index);
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ChangeVarNodes((Node *) rule_action->targetList,
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PRS2_CURRENT_VARNO + rt_length, rt_index);
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ChangeVarNodes(rule_qual, PRS2_CURRENT_VARNO + rt_length, rt_index);
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if (relation_level)
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{
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HandleViewRule(parsetree, rtable, rule_action->targetList, rt_index,
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modified);
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}
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else
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{
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HandleRIRAttributeRule(parsetree, rtable, rule_action->targetList,
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rt_index, rule->attrno, modified, &badsql);
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}
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if (*modified && !badsql)
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AddQual(parsetree, rule_action->qual);
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}
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static List *
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ProcessRetrieveQuery(Query *parsetree,
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List *rtable,
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bool *instead_flag,
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bool rule)
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{
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List *rt;
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List *product_queries = NIL;
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int rt_index = 0;
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foreach(rt, rtable)
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{
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RangeTblEntry *rt_entry = lfirst(rt);
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Relation rt_entry_relation = NULL;
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List *result = NIL;
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rt_index++;
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rt_entry_relation = heap_openr(rt_entry->relname);
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if (rt_entry_relation->rd_rules != NULL)
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{
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result =
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FireRetrieveRulesAtQuery(parsetree,
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rt_index,
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rt_entry_relation,
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instead_flag,
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rule);
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}
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heap_close(rt_entry_relation);
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if (*instead_flag)
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return result;
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}
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if (rule)
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return NIL;
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foreach(rt, rtable)
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{
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RangeTblEntry *rt_entry = lfirst(rt);
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Relation rt_entry_relation = NULL;
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RuleLock *rt_entry_locks = NULL;
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List *result = NIL;
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List *locks = NIL;
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List *dummy_products;
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rt_index++;
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rt_entry_relation = heap_openr(rt_entry->relname);
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rt_entry_locks = rt_entry_relation->rd_rules;
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heap_close(rt_entry_relation);
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if (rt_entry_locks)
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{
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locks =
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matchLocks(CMD_SELECT, rt_entry_locks, rt_index, parsetree);
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}
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if (locks != NIL)
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{
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result = fireRules(parsetree, rt_index, CMD_SELECT,
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instead_flag, locks, &dummy_products);
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if (*instead_flag)
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return lappend(NIL, result);
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if (result != NIL)
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product_queries = nconc(product_queries, result);
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}
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}
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return product_queries;
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}
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static Query *
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CopyAndAddQual(Query *parsetree,
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List *actions,
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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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Query *new_tree = (Query *) copyObject(parsetree);
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Node *new_qual = NULL;
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Query *rule_action = NULL;
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if (actions)
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rule_action = lfirst(actions);
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if (rule_qual != NULL)
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new_qual = (Node *) copyObject(rule_qual);
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if (rule_action != NULL)
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{
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List *rtable;
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int rt_length;
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rtable = new_tree->rtable;
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rt_length = length(rtable);
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rtable = append(rtable, listCopy(rule_action->rtable));
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new_tree->rtable = rtable;
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OffsetVarNodes(new_qual, rt_length);
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ChangeVarNodes(new_qual, PRS2_CURRENT_VARNO + rt_length, rt_index);
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}
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/* XXX -- where current doesn't work for instead nothing.... yet */
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AddNotQual(new_tree, new_qual);
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return new_tree;
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}
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/*
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* fireRules -
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* Iterate through rule locks applying rules. After an instead rule
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* rule has been applied, return just new parsetree and let RewriteQuery
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* start the process all over again. The locks are reordered to maintain
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* sensible semantics. remember: reality is for dead birds -- glass
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*
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*/
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static List *
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fireRules(Query *parsetree,
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int rt_index,
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CmdType event,
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bool *instead_flag,
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List *locks,
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List **qual_products)
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{
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RewriteInfo *info;
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List *results = NIL;
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List *i;
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/* choose rule to fire from list of rules */
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if (locks == NIL)
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{
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ProcessRetrieveQuery(parsetree,
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parsetree->rtable,
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instead_flag, TRUE);
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if (*instead_flag)
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return lappend(NIL, parsetree);
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else
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return NIL;
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}
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locks = orderRules(locks); /* instead rules first */
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foreach(i, locks)
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{
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RewriteRule *rule_lock = (RewriteRule *) lfirst(i);
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Node *qual,
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*event_qual;
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List *actions;
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List *r;
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bool orig_instead_flag = *instead_flag;
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/* multiple rule action time */
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*instead_flag = rule_lock->isInstead;
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event_qual = rule_lock->qual;
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actions = rule_lock->actions;
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if (event_qual != NULL && *instead_flag)
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*qual_products =
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lappend(*qual_products,
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CopyAndAddQual(parsetree, actions, event_qual,
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rt_index, event));
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foreach(r, actions)
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{
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Query *rule_action = lfirst(r);
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Node *rule_qual = copyObject(event_qual);
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/*--------------------------------------------------
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* Step 1:
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* Rewrite current.attribute or current to tuple variable
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* this appears to be done in parser?
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*--------------------------------------------------
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*/
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info = gatherRewriteMeta(parsetree, rule_action, rule_qual,
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rt_index, event, instead_flag);
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/* handle escapable cases, or those handled by other code */
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if (info->nothing)
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{
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if (*instead_flag)
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return NIL;
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else
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continue;
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}
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if (info->action == info->event &&
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info->event == CMD_SELECT)
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continue;
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/*
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* Event Qualification forces copying of parsetree --- XXX and
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* splitting into two queries one w/rule_qual, one w/NOT
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* rule_qual. Also add user query qual onto rule action
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*/
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qual = parsetree->qual;
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AddQual(info->rule_action, qual);
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if (info->rule_qual != NULL)
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AddQual(info->rule_action, info->rule_qual);
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/*--------------------------------------------------
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* Step 2:
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* Rewrite new.attribute w/ right hand side of target-list
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* entry for appropriate field name in insert/update
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*--------------------------------------------------
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*/
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if ((info->event == CMD_INSERT) || (info->event == CMD_UPDATE))
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{
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FixNew(info, parsetree);
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}
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/*--------------------------------------------------
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* Step 3:
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* rewriting due to retrieve rules
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*--------------------------------------------------
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*/
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info->rule_action->rtable = info->rt;
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ProcessRetrieveQuery(info->rule_action, info->rt,
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&orig_instead_flag, TRUE);
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/*--------------------------------------------------
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* Step 4
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* Simplify? hey, no algorithm for simplification... let
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* the planner do it.
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*--------------------------------------------------
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*/
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results = lappend(results, info->rule_action);
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pfree(info);
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}
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if (*instead_flag)
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break;
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}
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return results;
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}
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static List *
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RewriteQuery(Query *parsetree, bool *instead_flag, List **qual_products)
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{
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CmdType event;
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List *product_queries = NIL;
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int result_relation = 0;
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Assert(parsetree != NULL);
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event = parsetree->commandType;
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if (event == CMD_UTILITY)
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return NIL;
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/*
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* only for a delete may the targetlist be NULL
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*/
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if (event != CMD_DELETE)
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{
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Assert(parsetree->targetList != NULL);
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}
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result_relation = parsetree->resultRelation;
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if (event != CMD_SELECT)
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{
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/*
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* the statement is an update, insert or delete
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*/
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RangeTblEntry *rt_entry;
|
|
Relation rt_entry_relation = NULL;
|
|
RuleLock *rt_entry_locks = NULL;
|
|
|
|
rt_entry = rt_fetch(result_relation, parsetree->rtable);
|
|
rt_entry_relation = heap_openr(rt_entry->relname);
|
|
rt_entry_locks = rt_entry_relation->rd_rules;
|
|
heap_close(rt_entry_relation);
|
|
|
|
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);
|
|
}
|
|
return product_queries;
|
|
}
|
|
else
|
|
{
|
|
|
|
/*
|
|
* the statement is a select
|
|
*/
|
|
Query *other;
|
|
|
|
other = copyObject(parsetree); /* ApplyRetrieveRule changes the
|
|
* range table */
|
|
return
|
|
ProcessRetrieveQuery(other, parsetree->rtable,
|
|
instead_flag, FALSE);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* to avoid infinite recursion, we restrict the number of times a query
|
|
* can be rewritten. Detecting cycles is left for the reader as an excercise.
|
|
*/
|
|
#ifndef REWRITE_INVOKE_MAX
|
|
#define REWRITE_INVOKE_MAX 10
|
|
#endif
|
|
|
|
static int numQueryRewriteInvoked = 0;
|
|
|
|
/*
|
|
* QueryRewrite -
|
|
* rewrite one query via QueryRewrite system, possibly returning 0, or many
|
|
* queries
|
|
*/
|
|
List *
|
|
QueryRewrite(Query *parsetree)
|
|
{
|
|
numQueryRewriteInvoked = 0;
|
|
|
|
/*
|
|
* take a deep breath and apply all the rewrite rules - ay
|
|
*/
|
|
return deepRewriteQuery(parsetree);
|
|
}
|
|
|
|
/*
|
|
* 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 = NIL;
|
|
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);
|
|
if (!instead)
|
|
rewritten = lcons(parsetree, NIL);
|
|
|
|
foreach(n, result)
|
|
{
|
|
Query *pt = lfirst(n);
|
|
List *newstuff = NIL;
|
|
|
|
newstuff = deepRewriteQuery(pt);
|
|
if (newstuff != NIL)
|
|
rewritten = nconc(rewritten, newstuff);
|
|
}
|
|
if (qual_products != NIL)
|
|
rewritten = nconc(rewritten, qual_products);
|
|
|
|
return rewritten;
|
|
}
|