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Postgres95 1.01 Distribution - Virgin Sources
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Marc G. Fournier
325
src/backend/commands/view.c
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325
src/backend/commands/view.c
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/*-------------------------------------------------------------------------
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*
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* view.c--
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* use rewrite rules to construct views
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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/commands/view.c,v 1.1.1.1 1996/07/09 06:21:22 scrappy Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include <stdio.h> /* for sprintf() */
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#include "postgres.h"
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#include "access/heapam.h"
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#include "access/xact.h"
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#include "utils/builtins.h"
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#include "utils/syscache.h"
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#include "utils/elog.h"
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#include "utils/palloc.h"
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#include "nodes/relation.h"
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#include "nodes/primnodes.h"
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#include "nodes/parsenodes.h"
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#include "parser/catalog_utils.h"
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#include "parser/parse_query.h"
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#include "rewrite/rewriteDefine.h"
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#include "rewrite/rewriteHandler.h"
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#include "rewrite/rewriteManip.h"
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#include "rewrite/rewriteRemove.h"
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#include "commands/creatinh.h"
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/*---------------------------------------------------------------------
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* DefineVirtualRelation
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*
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* Create the "view" relation.
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* `DefineRelation' does all the work, we just provide the correct
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* arguments!
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*
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* If the relation already exists, then 'DefineRelation' will abort
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* the xact...
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*---------------------------------------------------------------------
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*/
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static void
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DefineVirtualRelation(char *relname, List *tlist)
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{
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CreateStmt createStmt;
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List *attrList, *t;
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TargetEntry *entry;
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Resdom *res;
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char *resname;
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char *restypename;
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/*
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* create a list with one entry per attribute of this relation.
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* Each entry is a two element list. The first element is the
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* name of the attribute (a string) and the second the name of the type
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* (NOTE: a string, not a type id!).
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*/
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attrList = NIL;
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if (tlist!=NIL) {
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foreach (t, tlist ) {
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ColumnDef *def = makeNode(ColumnDef);
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TypeName *typename;
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/*
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* find the names of the attribute & its type
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*/
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entry = lfirst(t);
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res = entry->resdom;
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resname = res->resname;
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restypename = tname(get_id_type((long)res->restype));
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typename = makeNode(TypeName);
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typename->name = pstrdup(restypename);
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def->colname = pstrdup(resname);
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def->typename = typename;
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attrList = lappend(attrList, def);
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}
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} else {
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elog ( WARN, "attempted to define virtual relation with no attrs");
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}
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/*
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* now create the parametesr for keys/inheritance etc.
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* All of them are nil...
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*/
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createStmt.relname = relname;
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createStmt.tableElts = attrList;
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/* createStmt.tableType = NULL;*/
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createStmt.inhRelnames = NIL;
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createStmt.archiveType = ARCH_NONE;
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createStmt.location = -1;
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createStmt.archiveLoc = -1;
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/*
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* finally create the relation...
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*/
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DefineRelation(&createStmt);
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}
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/*------------------------------------------------------------------
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* makeViewRetrieveRuleName
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*
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* Given a view name, returns the name for the 'on retrieve to "view"'
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* rule.
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* This routine is called when defining/removing a view.
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*
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* NOTE: it quarantees that the name is at most 15 chars long
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*
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* XXX it also means viewName cannot be 16 chars long! - ay 11/94
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*------------------------------------------------------------------
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*/
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char *
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MakeRetrieveViewRuleName(char *viewName)
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{
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/*
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char buf[100];
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memset(buf, 0, sizeof(buf));
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sprintf(buf, "_RET%.*s", NAMEDATALEN, viewName->data);
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buf[15] = '\0';
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namestrcpy(rule_name, buf);
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*/
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char *buf;
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buf = palloc(strlen(viewName) + 5);
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sprintf(buf, "_RET%s",viewName);
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return buf;
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}
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static RuleStmt *
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FormViewRetrieveRule(char *viewName, Query *viewParse)
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{
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RuleStmt *rule;
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char *rname;
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Attr *attr;
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/*
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* Create a RuleStmt that corresponds to the suitable
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* rewrite rule args for DefineQueryRewrite();
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*/
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rule = makeNode(RuleStmt);
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rname = MakeRetrieveViewRuleName(viewName);
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attr = makeNode(Attr);
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attr->relname = pstrdup(viewName);
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/* attr->refname = pstrdup(viewName);*/
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rule->rulename = pstrdup(rname);
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rule->whereClause = NULL;
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rule->event = CMD_SELECT;
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rule->object = attr;
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rule->instead = true;
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rule->actions = lcons(viewParse, NIL);
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return rule;
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}
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static void
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DefineViewRules(char *viewName, Query *viewParse)
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{
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RuleStmt *retrieve_rule = NULL;
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#ifdef NOTYET
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RuleStmt *replace_rule = NULL;
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RuleStmt *append_rule = NULL;
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RuleStmt *delete_rule = NULL;
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#endif
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retrieve_rule =
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FormViewRetrieveRule(viewName, viewParse);
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#ifdef NOTYET
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replace_rule =
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FormViewReplaceRule(viewName, viewParse);
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append_rule =
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FormViewAppendRule(viewName, viewParse);
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delete_rule =
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FormViewDeleteRule(viewName, viewParse);
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#endif
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DefineQueryRewrite(retrieve_rule);
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#ifdef NOTYET
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DefineQueryRewrite(replace_rule);
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DefineQueryRewrite(append_rule);
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DefineQueryRewrite(delete_rule);
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#endif
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}
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/*---------------------------------------------------------------
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* UpdateRangeTableOfViewParse
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*
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* Update the range table of the given parsetree.
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* This update consists of adding two new entries IN THE BEGINNING
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* of the range table (otherwise the rule system will die a slow,
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* horrible and painful death, and we do not want that now, do we?)
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* one for the CURRENT relation and one for the NEW one (both of
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* them refer in fact to the "view" relation).
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*
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* Of course we must also increase the 'varnos' of all the Var nodes
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* by 2...
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*
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* NOTE: these are destructive changes. It would be difficult to
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* make a complete copy of the parse tree and make the changes
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* in the copy.
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*---------------------------------------------------------------
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*/
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static void
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UpdateRangeTableOfViewParse(char *viewName, Query *viewParse)
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{
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List *old_rt;
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List *new_rt;
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RangeTblEntry *rt_entry1, *rt_entry2;
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/*
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* first offset all var nodes by 2
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*/
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OffsetVarNodes((Node*)viewParse->targetList, 2);
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OffsetVarNodes(viewParse->qual, 2);
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/*
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* find the old range table...
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*/
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old_rt = viewParse->rtable;
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/*
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* create the 2 new range table entries and form the new
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* range table...
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* CURRENT first, then NEW....
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*/
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rt_entry1 =
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makeRangeTableEntry((char*)viewName, FALSE, NULL, "*CURRENT*");
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rt_entry2 =
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makeRangeTableEntry((char*)viewName, FALSE, NULL, "*NEW*");
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new_rt = lcons(rt_entry2, old_rt);
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new_rt = lcons(rt_entry1, new_rt);
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/*
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* Now the tricky part....
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* Update the range table in place... Be careful here, or
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* hell breaks loooooooooooooOOOOOOOOOOOOOOOOOOSE!
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*/
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viewParse->rtable = new_rt;
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}
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/*-------------------------------------------------------------------
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* DefineView
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*
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* - takes a "viewname", "parsetree" pair and then
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* 1) construct the "virtual" relation
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* 2) commit the command but NOT the transaction,
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* so that the relation exists
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* before the rules are defined.
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* 2) define the "n" rules specified in the PRS2 paper
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* over the "virtual" relation
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*-------------------------------------------------------------------
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*/
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void
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DefineView(char *viewName, Query *viewParse)
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{
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List *viewTlist;
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viewTlist = viewParse->targetList;
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/*
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* Create the "view" relation
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* NOTE: if it already exists, the xaxt will be aborted.
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*/
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DefineVirtualRelation(viewName, viewTlist);
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/*
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* The relation we have just created is not visible
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* to any other commands running with the same transaction &
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* command id.
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* So, increment the command id counter (but do NOT pfree any
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* memory!!!!)
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*/
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CommandCounterIncrement();
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/*
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* The range table of 'viewParse' does not contain entries
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* for the "CURRENT" and "NEW" relations.
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* So... add them!
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* NOTE: we make the update in place! After this call 'viewParse'
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* will never be what it used to be...
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*/
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UpdateRangeTableOfViewParse(viewName, viewParse);
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DefineViewRules(viewName, viewParse);
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}
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/*------------------------------------------------------------------
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* RemoveView
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*
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* Remove a view given its name
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*------------------------------------------------------------------
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*/
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void
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RemoveView(char *viewName)
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{
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char* rname;
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/*
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* first remove all the "view" rules...
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* Currently we only have one!
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*/
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rname = MakeRetrieveViewRuleName(viewName);
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RemoveRewriteRule(rname);
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/*
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* we don't really need that, but just in case...
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*/
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CommandCounterIncrement();
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/*
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* now remove the relation.
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*/
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heap_destroy(viewName);
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pfree(rname);
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}
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