3a94e789f5
(Don't forget that an alias is required.) Views reimplemented as expanding to subselect-in-FROM. Grouping, aggregates, DISTINCT in views actually work now (he says optimistically). No UNION support in subselects/views yet, but I have some ideas about that. Rule-related permissions checking moved out of rewriter and into executor. INITDB REQUIRED!
298 lines
7.7 KiB
C
298 lines
7.7 KiB
C
/*-------------------------------------------------------------------------
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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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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: view.c,v 1.49 2000/09/29 18:21:26 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/xact.h"
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#include "catalog/heap.h"
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#include "commands/creatinh.h"
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#include "commands/view.h"
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#include "miscadmin.h"
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#include "nodes/makefuncs.h"
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#include "parser/parse_relation.h"
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#include "parser/parse_type.h"
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#include "rewrite/rewriteDefine.h"
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#include "rewrite/rewriteManip.h"
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#include "rewrite/rewriteRemove.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 = makeNode(CreateStmt);
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List *attrList,
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*t;
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/*
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* create a list of ColumnDef nodes based on the names and types of
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* the (non-junk) targetlist items from the view's SELECT list.
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*/
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attrList = NIL;
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foreach(t, tlist)
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{
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TargetEntry *entry = lfirst(t);
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Resdom *res = entry->resdom;
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if (! res->resjunk)
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{
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char *resname = res->resname;
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char *restypename = typeidTypeName(res->restype);
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ColumnDef *def = makeNode(ColumnDef);
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TypeName *typename = makeNode(TypeName);
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def->colname = pstrdup(resname);
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typename->name = pstrdup(restypename);
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typename->typmod = res->restypmod;
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def->typename = typename;
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def->is_not_null = false;
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def->is_sequence = false;
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def->raw_default = NULL;
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def->cooked_default = NULL;
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def->constraints = NIL;
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attrList = lappend(attrList, def);
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}
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}
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if (attrList == NIL)
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elog(ERROR, "attempted to define virtual relation with no attrs");
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/*
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* now create the parameters for keys/inheritance etc. All of them are
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* nil...
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*/
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createStmt->relname = relname;
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createStmt->istemp = false;
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createStmt->tableElts = attrList;
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createStmt->inhRelnames = NIL;
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createStmt->constraints = NIL;
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/*
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* finally create the relation...
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*/
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DefineRelation(createStmt, RELKIND_VIEW);
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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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*------------------------------------------------------------------
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*/
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char *
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MakeRetrieveViewRuleName(char *viewName)
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{
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char *buf;
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#ifdef MULTIBYTE
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int len;
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#endif
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buf = palloc(strlen(viewName) + 5);
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snprintf(buf, strlen(viewName) + 5, "_RET%s", viewName);
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#ifdef MULTIBYTE
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len = pg_mbcliplen(buf,strlen(buf),NAMEDATALEN-1);
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buf[len] = '\0';
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#else
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buf[NAMEDATALEN-1] = '\0';
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#endif
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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 rewrite rule
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* 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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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 = makeList1(viewParse);
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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 = FormViewRetrieveRule(viewName, viewParse);
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#ifdef NOTYET
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replace_rule = FormViewReplaceRule(viewName, viewParse);
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append_rule = FormViewAppendRule(viewName, viewParse);
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delete_rule = 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 OLD 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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* These extra RT entries are not actually used in the query, obviously.
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* We add them so that views look the same as ON SELECT rules ---
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* the rule rewriter assumes that ALL rules have OLD and NEW RTEs.
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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 *new_rt;
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RangeTblEntry *rt_entry1,
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*rt_entry2;
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/*
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* create the 2 new range table entries and form the new range
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* table... OLD first, then NEW....
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*/
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rt_entry1 = addRangeTableEntry(NULL, viewName,
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makeAttr("*OLD*", NULL),
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false, false);
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rt_entry2 = addRangeTableEntry(NULL, viewName,
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makeAttr("*NEW*", NULL),
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false, false);
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/* Must override addRangeTableEntry's default access-check flags */
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rt_entry1->checkForRead = false;
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rt_entry2->checkForRead = false;
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new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable));
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/*
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* Now the tricky part.... Update the range table in place... Be
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* careful here, or hell breaks loooooooooooooOOOOOOOOOOOOOOOOOOSE!
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*/
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viewParse->rtable = new_rt;
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/*
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* now offset all var nodes by 2, and jointree RT indexes too.
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*/
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OffsetVarNodes((Node *) viewParse, 2, 0);
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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 NOTE: if it already exists, the xact
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* 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 to any other
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* commands running with the same transaction & command id. So,
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* increment the command id counter (but do NOT pfree any 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 for the
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* "OLD" and "NEW" relations. So... add them! NOTE: we make the
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* update in place! After this call 'viewParse' will never be what it
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* 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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/*
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* We just have to drop the relation; the associated rules will
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* be cleaned up automatically.
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*/
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heap_drop_with_catalog(viewName, allowSystemTableMods);
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}
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