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maintained for each cache entry. A cache entry will not be freed until the matching ReleaseSysCache call has been executed. This eliminates worries about cache entries getting dropped while still in use. See my posting to pg-hackers of even date for more info.
1215 lines
35 KiB
C
1215 lines
35 KiB
C
/*-------------------------------------------------------------------------
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*
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* parse_clause.c
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* handle clauses in parser
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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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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.73 2000/11/16 22:30:27 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 "nodes/makefuncs.h"
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#include "optimizer/tlist.h"
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#include "optimizer/var.h"
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#include "parser/analyze.h"
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#include "parser/parse.h"
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#include "parser/parsetree.h"
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#include "parser/parse_clause.h"
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#include "parser/parse_coerce.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_relation.h"
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#include "parser/parse_target.h"
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#include "parser/parse_type.h"
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#define ORDER_CLAUSE 0
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#define GROUP_CLAUSE 1
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#define DISTINCT_ON_CLAUSE 2
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static char *clauseText[] = {"ORDER BY", "GROUP BY", "DISTINCT ON"};
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static void extractUniqueColumns(List *common_colnames,
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List *src_colnames, List *src_colvars,
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List **res_colnames, List **res_colvars);
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static Node *transformJoinUsingClause(ParseState *pstate,
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List *leftVars, List *rightVars);
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static Node *transformJoinOnClause(ParseState *pstate, JoinExpr *j,
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List *containedRels);
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static RangeTblRef *transformTableEntry(ParseState *pstate, RangeVar *r);
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static RangeTblRef *transformRangeSubselect(ParseState *pstate,
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RangeSubselect *r);
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static Node *transformFromClauseItem(ParseState *pstate, Node *n,
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List **containedRels);
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static TargetEntry *findTargetlistEntry(ParseState *pstate, Node *node,
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List *tlist, int clause);
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static List *addTargetToSortList(TargetEntry *tle, List *sortlist,
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List *targetlist, char *opname);
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static bool exprIsInSortList(Node *expr, List *sortList, List *targetList);
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/*
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* makeRangeTable -
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* Build the initial range table from the FROM clause.
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*
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* The range table constructed here may grow as we transform the expressions
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* in the query's quals and target list. (Note that this happens because in
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* POSTQUEL, we allow references to relations not specified in the
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* from-clause. PostgreSQL keeps this extension to standard SQL.)
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*
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* Note: we assume that pstate's p_rtable and p_joinlist lists were
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* initialized to NIL when the pstate was created. We will add onto
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* any entries already present --- this is needed for rule processing!
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*/
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void
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makeRangeTable(ParseState *pstate, List *frmList)
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{
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List *fl;
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/*
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* The grammar will have produced a list of RangeVars, RangeSubselects,
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* and/or JoinExprs. Transform each one, and then add it to the joinlist.
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*/
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foreach(fl, frmList)
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{
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Node *n = lfirst(fl);
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List *containedRels;
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n = transformFromClauseItem(pstate, n, &containedRels);
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pstate->p_joinlist = lappend(pstate->p_joinlist, n);
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}
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}
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/*
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* lockTargetTable
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* Find the target relation of INSERT/UPDATE/DELETE and acquire write
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* lock on it. This must be done before building the range table,
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* in case the target is also mentioned as a source relation --- we
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* want to be sure to grab the write lock before any read lock.
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*
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* The ParseState's link to the target relcache entry is also set here.
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*/
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void
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lockTargetTable(ParseState *pstate, char *relname)
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{
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/* Close old target; this could only happen for multi-action rules */
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if (pstate->p_target_relation != NULL)
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heap_close(pstate->p_target_relation, NoLock);
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pstate->p_target_relation = NULL;
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pstate->p_target_rangetblentry = NULL; /* setTargetTable will set this */
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/*
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* Open target rel and grab suitable lock (which we will hold till
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* end of transaction).
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*
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* analyze.c will eventually do the corresponding heap_close(),
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* but *not* release the lock.
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*/
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pstate->p_target_relation = heap_openr(relname, RowExclusiveLock);
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}
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/*
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* setTargetTable
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* Add the target relation of INSERT/UPDATE/DELETE to the range table,
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* and make the special links to it in the ParseState.
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*
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* inJoinSet says whether to add the target to the join list.
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* For INSERT, we don't want the target to be joined to; it's a
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* destination of tuples, not a source. For UPDATE/DELETE, we do
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* need to scan or join the target.
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*/
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void
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setTargetTable(ParseState *pstate, char *relname, bool inh, bool inJoinSet)
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{
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RangeTblEntry *rte;
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/* look for relname only at current nesting level... */
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if (refnameRangeTablePosn(pstate, relname, NULL) == 0)
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{
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rte = addRangeTableEntry(pstate, relname, NULL, inh, false);
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/*
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* Since the rel wasn't in the rangetable already, it's not being
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* read; override addRangeTableEntry's default checkForRead.
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*
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* If we find an explicit reference to the rel later during
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* parse analysis, scanRTEForColumn will change checkForRead
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* to 'true' again. That can't happen for INSERT but it is
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* possible for UPDATE and DELETE.
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*/
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rte->checkForRead = false;
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}
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else
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{
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rte = refnameRangeTableEntry(pstate, relname);
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/*
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* Since the rel was in the rangetable already, it's being read
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* as well as written. Therefore, leave checkForRead true.
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*
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* Force inh to the desired setting for the target (XXX is this
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* reasonable? It's *necessary* that INSERT target not be marked
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* inheritable, but otherwise not too clear what to do if conflict?)
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*/
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rte->inh = inh;
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}
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/* Mark target table as requiring write access. */
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rte->checkForWrite = true;
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if (inJoinSet)
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addRTEtoJoinList(pstate, rte);
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/* lockTargetTable should have been called earlier */
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Assert(pstate->p_target_relation != NULL);
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pstate->p_target_rangetblentry = rte;
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}
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/*
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* Extract all not-in-common columns from column lists of a source table
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*/
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static void
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extractUniqueColumns(List *common_colnames,
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List *src_colnames, List *src_colvars,
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List **res_colnames, List **res_colvars)
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{
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List *new_colnames = NIL;
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List *new_colvars = NIL;
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List *lnames,
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*lvars = src_colvars;
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foreach(lnames, src_colnames)
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{
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char *colname = strVal(lfirst(lnames));
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bool match = false;
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List *cnames;
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foreach(cnames, common_colnames)
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{
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char *ccolname = strVal(lfirst(cnames));
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if (strcmp(colname, ccolname) == 0)
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{
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match = true;
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break;
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}
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}
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if (!match)
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{
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new_colnames = lappend(new_colnames, lfirst(lnames));
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new_colvars = lappend(new_colvars, lfirst(lvars));
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}
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lvars = lnext(lvars);
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}
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*res_colnames = new_colnames;
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*res_colvars = new_colvars;
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}
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/* transformJoinUsingClause()
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* Build a complete ON clause from a partially-transformed USING list.
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* We are given lists of nodes representing left and right match columns.
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* Result is a transformed qualification expression.
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*/
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static Node *
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transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars)
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{
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Node *result = NULL;
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List *lvars,
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*rvars = rightVars;
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/*
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* We cheat a little bit here by building an untransformed operator
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* tree whose leaves are the already-transformed Vars. This is OK
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* because transformExpr() won't complain about already-transformed
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* subnodes.
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*/
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foreach(lvars, leftVars)
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{
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Node *lvar = (Node *) lfirst(lvars);
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Node *rvar = (Node *) lfirst(rvars);
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A_Expr *e;
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e = makeNode(A_Expr);
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e->oper = OP;
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e->opname = "=";
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e->lexpr = copyObject(lvar);
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e->rexpr = copyObject(rvar);
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if (result == NULL)
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result = (Node *) e;
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else
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{
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A_Expr *a = makeNode(A_Expr);
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a->oper = AND;
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a->opname = NULL;
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a->lexpr = result;
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a->rexpr = (Node *) e;
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result = (Node *) a;
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}
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rvars = lnext(rvars);
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}
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/*
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* Since the references are already Vars, and are certainly from the
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* input relations, we don't have to go through the same pushups that
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* transformJoinOnClause() does. Just invoke transformExpr() to fix
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* up the operators, and we're done.
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*/
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result = transformExpr(pstate, result, EXPR_COLUMN_FIRST);
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if (exprType(result) != BOOLOID)
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{
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/* This could only happen if someone defines a funny version of '=' */
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elog(ERROR, "JOIN/USING clause must return type bool, not type %s",
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typeidTypeName(exprType(result)));
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}
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return result;
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} /* transformJoinUsingClause() */
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/* transformJoinOnClause()
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* Transform the qual conditions for JOIN/ON.
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* Result is a transformed qualification expression.
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*/
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static Node *
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transformJoinOnClause(ParseState *pstate, JoinExpr *j,
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List *containedRels)
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{
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Node *result;
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List *sv_joinlist;
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List *clause_varnos,
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*l;
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/*
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* This is a tad tricky, for two reasons. First, at the point where
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* we're called, the two subtrees of the JOIN node aren't yet part of
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* the pstate's joinlist, which means that transformExpr() won't resolve
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* unqualified references to their columns correctly. We fix this in a
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* slightly klugy way: temporarily make the pstate's joinlist consist of
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* just those two subtrees (which creates exactly the namespace the ON
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* clause should see). This is OK only because the ON clause can't
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* legally alter the joinlist by causing relation refs to be added.
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*/
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sv_joinlist = pstate->p_joinlist;
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pstate->p_joinlist = makeList2(j->larg, j->rarg);
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/* This part is just like transformWhereClause() */
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result = transformExpr(pstate, j->quals, EXPR_COLUMN_FIRST);
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if (exprType(result) != BOOLOID)
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{
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elog(ERROR, "JOIN/ON clause must return type bool, not type %s",
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typeidTypeName(exprType(result)));
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}
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pstate->p_joinlist = sv_joinlist;
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/*
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* Second, we need to check that the ON condition doesn't refer to any
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* rels outside the input subtrees of the JOIN. It could do that despite
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* our hack on the joinlist if it uses fully-qualified names. So, grovel
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* through the transformed clause and make sure there are no bogus
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* references.
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*/
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clause_varnos = pull_varnos(result);
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foreach(l, clause_varnos)
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{
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int varno = lfirsti(l);
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if (! intMember(varno, containedRels))
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{
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elog(ERROR, "JOIN/ON clause refers to \"%s\", which is not part of JOIN",
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rt_fetch(varno, pstate->p_rtable)->eref->relname);
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}
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}
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freeList(clause_varnos);
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return result;
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}
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/*
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* transformTableEntry --- transform a RangeVar (simple relation reference)
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*/
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static RangeTblRef *
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transformTableEntry(ParseState *pstate, RangeVar *r)
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{
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char *relname = r->relname;
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RangeTblEntry *rte;
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RangeTblRef *rtr;
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/*
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* mark this entry to indicate it comes from the FROM clause. In SQL,
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* the target list can only refer to range variables specified in the
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* from clause but we follow the more powerful POSTQUEL semantics and
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* automatically generate the range variable if not specified. However
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* there are times we need to know whether the entries are legitimate.
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*/
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rte = addRangeTableEntry(pstate, relname, r->name, r->inh, true);
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/*
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* We create a RangeTblRef, but we do not add it to the joinlist here.
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* makeRangeTable will do so, if we are at top level of the FROM clause.
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*/
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rtr = makeNode(RangeTblRef);
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/* assume new rte is at end */
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rtr->rtindex = length(pstate->p_rtable);
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Assert(rte == rt_fetch(rtr->rtindex, pstate->p_rtable));
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return rtr;
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}
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/*
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* transformRangeSubselect --- transform a sub-SELECT appearing in FROM
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*/
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static RangeTblRef *
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transformRangeSubselect(ParseState *pstate, RangeSubselect *r)
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{
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List *save_rtable;
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List *save_joinlist;
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List *parsetrees;
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Query *query;
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RangeTblEntry *rte;
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RangeTblRef *rtr;
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/*
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* We require user to supply an alias for a subselect, per SQL92.
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* To relax this, we'd have to be prepared to gin up a unique alias
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* for an unlabeled subselect.
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*/
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if (r->name == NULL)
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elog(ERROR, "sub-select in FROM must have an alias");
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/*
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* Analyze and transform the subquery. This is a bit tricky because
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* we don't want the subquery to be able to see any FROM items already
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* created in the current query (per SQL92, the scope of a FROM item
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* does not include other FROM items). But it does need to be able to
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* see any further-up parent states, so we can't just pass a null parent
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* pstate link. So, temporarily make the current query level have an
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* empty rtable and joinlist.
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*/
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save_rtable = pstate->p_rtable;
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save_joinlist = pstate->p_joinlist;
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pstate->p_rtable = NIL;
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pstate->p_joinlist = NIL;
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parsetrees = parse_analyze(r->subquery, pstate);
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pstate->p_rtable = save_rtable;
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pstate->p_joinlist = save_joinlist;
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/*
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* Check that we got something reasonable. Some of these conditions
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* are probably impossible given restrictions of the grammar, but
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* check 'em anyway.
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*/
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if (length(parsetrees) != 1)
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elog(ERROR, "Unexpected parse analysis result for subselect in FROM");
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query = (Query *) lfirst(parsetrees);
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if (query == NULL || !IsA(query, Query))
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elog(ERROR, "Unexpected parse analysis result for subselect in FROM");
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if (query->commandType != CMD_SELECT)
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elog(ERROR, "Expected SELECT query from subselect in FROM");
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if (query->resultRelation != 0 || query->into != NULL || query->isPortal)
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elog(ERROR, "Subselect in FROM may not have SELECT INTO");
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/*
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* OK, build an RTE for the subquery.
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*/
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rte = addRangeTableEntryForSubquery(pstate, query, r->name, true);
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/*
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* We create a RangeTblRef, but we do not add it to the joinlist here.
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* makeRangeTable will do so, if we are at top level of the FROM clause.
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*/
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rtr = makeNode(RangeTblRef);
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/* assume new rte is at end */
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rtr->rtindex = length(pstate->p_rtable);
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Assert(rte == rt_fetch(rtr->rtindex, pstate->p_rtable));
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return rtr;
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}
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/*
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* transformFromClauseItem -
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* Transform a FROM-clause item, adding any required entries to the
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* range table list being built in the ParseState, and return the
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* transformed item ready to include in the joinlist.
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* This routine can recurse to handle SQL92 JOIN expressions.
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*
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* Aside from the primary return value (the transformed joinlist item)
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* this routine also returns an integer list of the rangetable indexes
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* of all the base relations represented in the joinlist item. This
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* list is needed for checking JOIN/ON conditions in higher levels.
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*/
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static Node *
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transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels)
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{
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if (IsA(n, RangeVar))
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{
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/* Plain relation reference */
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RangeTblRef *rtr;
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rtr = transformTableEntry(pstate, (RangeVar *) n);
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*containedRels = makeListi1(rtr->rtindex);
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return (Node *) rtr;
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}
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else if (IsA(n, RangeSubselect))
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{
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/* sub-SELECT is like a plain relation */
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RangeTblRef *rtr;
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rtr = transformRangeSubselect(pstate, (RangeSubselect *) n);
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*containedRels = makeListi1(rtr->rtindex);
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return (Node *) rtr;
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}
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else if (IsA(n, JoinExpr))
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{
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/* A newfangled join expression */
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JoinExpr *j = (JoinExpr *) n;
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List *l_containedRels,
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*r_containedRels,
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*l_colnames,
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*r_colnames,
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*res_colnames,
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*l_colvars,
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*r_colvars,
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*res_colvars;
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/*
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* Recursively process the left and right subtrees
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*/
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j->larg = transformFromClauseItem(pstate, j->larg, &l_containedRels);
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j->rarg = transformFromClauseItem(pstate, j->rarg, &r_containedRels);
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/*
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* Generate combined list of relation indexes
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*/
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*containedRels = nconc(l_containedRels, r_containedRels);
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/*
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* Extract column name and var lists from both subtrees
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*/
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if (IsA(j->larg, JoinExpr))
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{
|
|
/* Make a copy of the subtree's lists so we can modify! */
|
|
l_colnames = copyObject(((JoinExpr *) j->larg)->colnames);
|
|
l_colvars = copyObject(((JoinExpr *) j->larg)->colvars);
|
|
}
|
|
else
|
|
{
|
|
RangeTblEntry *rte;
|
|
|
|
Assert(IsA(j->larg, RangeTblRef));
|
|
rte = rt_fetch(((RangeTblRef *) j->larg)->rtindex,
|
|
pstate->p_rtable);
|
|
expandRTE(pstate, rte, &l_colnames, &l_colvars);
|
|
/* expandRTE returns new lists, so no need for copyObject */
|
|
}
|
|
if (IsA(j->rarg, JoinExpr))
|
|
{
|
|
/* Make a copy of the subtree's lists so we can modify! */
|
|
r_colnames = copyObject(((JoinExpr *) j->rarg)->colnames);
|
|
r_colvars = copyObject(((JoinExpr *) j->rarg)->colvars);
|
|
}
|
|
else
|
|
{
|
|
RangeTblEntry *rte;
|
|
|
|
Assert(IsA(j->rarg, RangeTblRef));
|
|
rte = rt_fetch(((RangeTblRef *) j->rarg)->rtindex,
|
|
pstate->p_rtable);
|
|
expandRTE(pstate, rte, &r_colnames, &r_colvars);
|
|
/* expandRTE returns new lists, so no need for copyObject */
|
|
}
|
|
|
|
/*
|
|
* Natural join does not explicitly specify columns; must
|
|
* generate columns to join. Need to run through the list of
|
|
* columns from each table or join result and match up the
|
|
* column names. Use the first table, and check every column
|
|
* in the second table for a match. (We'll check that the
|
|
* matches were unique later on.)
|
|
* The result of this step is a list of column names just like an
|
|
* explicitly-written USING list.
|
|
*/
|
|
if (j->isNatural)
|
|
{
|
|
List *rlist = NIL;
|
|
List *lx,
|
|
*rx;
|
|
|
|
Assert(j->using == NIL); /* shouldn't have USING() too */
|
|
|
|
foreach(lx, l_colnames)
|
|
{
|
|
char *l_colname = strVal(lfirst(lx));
|
|
Value *m_name = NULL;
|
|
|
|
foreach(rx, r_colnames)
|
|
{
|
|
char *r_colname = strVal(lfirst(rx));
|
|
|
|
if (strcmp(l_colname, r_colname) == 0)
|
|
{
|
|
m_name = makeString(l_colname);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* matched a right column? then keep as join column... */
|
|
if (m_name != NULL)
|
|
rlist = lappend(rlist, m_name);
|
|
}
|
|
|
|
j->using = rlist;
|
|
}
|
|
|
|
/*
|
|
* Now transform the join qualifications, if any.
|
|
*/
|
|
res_colnames = NIL;
|
|
res_colvars = NIL;
|
|
|
|
if (j->using)
|
|
{
|
|
/*
|
|
* JOIN/USING (or NATURAL JOIN, as transformed above).
|
|
* Transform the list into an explicit ON-condition,
|
|
* and generate a list of result columns.
|
|
*/
|
|
List *ucols = j->using;
|
|
List *l_usingvars = NIL;
|
|
List *r_usingvars = NIL;
|
|
List *ucol;
|
|
|
|
Assert(j->quals == NULL); /* shouldn't have ON() too */
|
|
|
|
foreach(ucol, ucols)
|
|
{
|
|
char *u_colname = strVal(lfirst(ucol));
|
|
List *col;
|
|
Node *l_colvar,
|
|
*r_colvar,
|
|
*colvar;
|
|
int ndx;
|
|
int l_index = -1;
|
|
int r_index = -1;
|
|
|
|
ndx = 0;
|
|
foreach(col, l_colnames)
|
|
{
|
|
char *l_colname = strVal(lfirst(col));
|
|
|
|
if (strcmp(l_colname, u_colname) == 0)
|
|
{
|
|
if (l_index >= 0)
|
|
elog(ERROR, "Common column name \"%s\" appears more than once in left table", u_colname);
|
|
l_index = ndx;
|
|
}
|
|
ndx++;
|
|
}
|
|
if (l_index < 0)
|
|
elog(ERROR, "JOIN/USING column \"%s\" not found in left table",
|
|
u_colname);
|
|
|
|
ndx = 0;
|
|
foreach(col, r_colnames)
|
|
{
|
|
char *r_colname = strVal(lfirst(col));
|
|
|
|
if (strcmp(r_colname, u_colname) == 0)
|
|
{
|
|
if (r_index >= 0)
|
|
elog(ERROR, "Common column name \"%s\" appears more than once in right table", u_colname);
|
|
r_index = ndx;
|
|
}
|
|
ndx++;
|
|
}
|
|
if (r_index < 0)
|
|
elog(ERROR, "JOIN/USING column \"%s\" not found in right table",
|
|
u_colname);
|
|
|
|
l_colvar = nth(l_index, l_colvars);
|
|
l_usingvars = lappend(l_usingvars, l_colvar);
|
|
r_colvar = nth(r_index, r_colvars);
|
|
r_usingvars = lappend(r_usingvars, r_colvar);
|
|
|
|
res_colnames = lappend(res_colnames,
|
|
nth(l_index, l_colnames));
|
|
switch (j->jointype)
|
|
{
|
|
case JOIN_INNER:
|
|
case JOIN_LEFT:
|
|
colvar = l_colvar;
|
|
break;
|
|
case JOIN_RIGHT:
|
|
colvar = r_colvar;
|
|
break;
|
|
default:
|
|
{
|
|
/* Need COALESCE(l_colvar, r_colvar) */
|
|
CaseExpr *c = makeNode(CaseExpr);
|
|
CaseWhen *w = makeNode(CaseWhen);
|
|
A_Expr *a = makeNode(A_Expr);
|
|
|
|
a->oper = NOTNULL;
|
|
a->lexpr = l_colvar;
|
|
w->expr = (Node *) a;
|
|
w->result = l_colvar;
|
|
c->args = makeList1(w);
|
|
c->defresult = r_colvar;
|
|
colvar = transformExpr(pstate, (Node *) c,
|
|
EXPR_COLUMN_FIRST);
|
|
break;
|
|
}
|
|
}
|
|
res_colvars = lappend(res_colvars, colvar);
|
|
}
|
|
|
|
j->quals = transformJoinUsingClause(pstate,
|
|
l_usingvars,
|
|
r_usingvars);
|
|
}
|
|
else if (j->quals)
|
|
{
|
|
/* User-written ON-condition; transform it */
|
|
j->quals = transformJoinOnClause(pstate, j, *containedRels);
|
|
}
|
|
else
|
|
{
|
|
/* CROSS JOIN: no quals */
|
|
}
|
|
|
|
/* Add remaining columns from each side to the output columns */
|
|
extractUniqueColumns(res_colnames,
|
|
l_colnames, l_colvars,
|
|
&l_colnames, &l_colvars);
|
|
extractUniqueColumns(res_colnames,
|
|
r_colnames, r_colvars,
|
|
&r_colnames, &r_colvars);
|
|
res_colnames = nconc(res_colnames, l_colnames);
|
|
res_colvars = nconc(res_colvars, l_colvars);
|
|
res_colnames = nconc(res_colnames, r_colnames);
|
|
res_colvars = nconc(res_colvars, r_colvars);
|
|
|
|
/*
|
|
* Process alias (AS clause), if any.
|
|
*
|
|
* The given table alias must be unique in the current nesting level,
|
|
* ie it cannot match any RTE refname or jointable alias. This is
|
|
* a bit painful to check because my own child joins are not yet in
|
|
* the pstate's joinlist, so they have to be scanned separately.
|
|
*/
|
|
if (j->alias)
|
|
{
|
|
/* Check against previously created RTEs and joinlist entries */
|
|
if (refnameRangeOrJoinEntry(pstate, j->alias->relname, NULL))
|
|
elog(ERROR, "Table name \"%s\" specified more than once",
|
|
j->alias->relname);
|
|
/* Check children */
|
|
if (scanJoinListForRefname(j->larg, j->alias->relname) ||
|
|
scanJoinListForRefname(j->rarg, j->alias->relname))
|
|
elog(ERROR, "Table name \"%s\" specified more than once",
|
|
j->alias->relname);
|
|
/*
|
|
* If a column alias list is specified, substitute the alias
|
|
* names into my output-column list
|
|
*/
|
|
if (j->alias->attrs != NIL)
|
|
{
|
|
if (length(j->alias->attrs) != length(res_colnames))
|
|
elog(ERROR, "Column alias list for \"%s\" has wrong number of entries (need %d)",
|
|
j->alias->relname, length(res_colnames));
|
|
res_colnames = j->alias->attrs;
|
|
}
|
|
}
|
|
|
|
j->colnames = res_colnames;
|
|
j->colvars = res_colvars;
|
|
|
|
return (Node *) j;
|
|
}
|
|
else
|
|
elog(ERROR, "transformFromClauseItem: unexpected node (internal error)"
|
|
"\n\t%s", nodeToString(n));
|
|
return NULL; /* can't get here, just keep compiler quiet */
|
|
}
|
|
|
|
|
|
/*
|
|
* transformWhereClause -
|
|
* transforms the qualification and make sure it is of type Boolean
|
|
*/
|
|
Node *
|
|
transformWhereClause(ParseState *pstate, Node *clause)
|
|
{
|
|
Node *qual;
|
|
|
|
if (clause == NULL)
|
|
return NULL;
|
|
|
|
qual = transformExpr(pstate, clause, EXPR_COLUMN_FIRST);
|
|
|
|
if (exprType(qual) != BOOLOID)
|
|
{
|
|
elog(ERROR, "WHERE clause must return type bool, not type %s",
|
|
typeidTypeName(exprType(qual)));
|
|
}
|
|
return qual;
|
|
}
|
|
|
|
|
|
/*
|
|
* findTargetlistEntry -
|
|
* Returns the targetlist entry matching the given (untransformed) node.
|
|
* If no matching entry exists, one is created and appended to the target
|
|
* list as a "resjunk" node.
|
|
*
|
|
* node the ORDER BY, GROUP BY, or DISTINCT ON expression to be matched
|
|
* tlist the existing target list (NB: this will never be NIL, which is a
|
|
* good thing since we'd be unable to append to it if it were...)
|
|
* clause identifies clause type being processed.
|
|
*/
|
|
static TargetEntry *
|
|
findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause)
|
|
{
|
|
TargetEntry *target_result = NULL;
|
|
List *tl;
|
|
Node *expr;
|
|
|
|
/*----------
|
|
* Handle two special cases as mandated by the SQL92 spec:
|
|
*
|
|
* 1. Bare ColumnName (no qualifier or subscripts)
|
|
* For a bare identifier, we search for a matching column name
|
|
* in the existing target list. Multiple matches are an error
|
|
* unless they refer to identical values; for example,
|
|
* we allow SELECT a, a FROM table ORDER BY a
|
|
* but not SELECT a AS b, b FROM table ORDER BY b
|
|
* If no match is found, we fall through and treat the identifier
|
|
* as an expression.
|
|
* For GROUP BY, it is incorrect to match the grouping item against
|
|
* targetlist entries: according to SQL92, an identifier in GROUP BY
|
|
* is a reference to a column name exposed by FROM, not to a target
|
|
* list column. However, many implementations (including pre-7.0
|
|
* PostgreSQL) accept this anyway. So for GROUP BY, we look first
|
|
* to see if the identifier matches any FROM column name, and only
|
|
* try for a targetlist name if it doesn't. This ensures that we
|
|
* adhere to the spec in the case where the name could be both.
|
|
* DISTINCT ON isn't in the standard, so we can do what we like there;
|
|
* we choose to make it work like ORDER BY, on the rather flimsy
|
|
* grounds that ordinary DISTINCT works on targetlist entries.
|
|
*
|
|
* 2. IntegerConstant
|
|
* This means to use the n'th item in the existing target list.
|
|
* Note that it would make no sense to order/group/distinct by an
|
|
* actual constant, so this does not create a conflict with our
|
|
* extension to order/group by an expression.
|
|
* GROUP BY column-number is not allowed by SQL92, but since
|
|
* the standard has no other behavior defined for this syntax,
|
|
* we may as well accept this common extension.
|
|
*
|
|
* Note that pre-existing resjunk targets must not be used in either case,
|
|
* since the user didn't write them in his SELECT list.
|
|
*
|
|
* If neither special case applies, fall through to treat the item as
|
|
* an expression.
|
|
*----------
|
|
*/
|
|
if (IsA(node, Ident) &&((Ident *) node)->indirection == NIL)
|
|
{
|
|
char *name = ((Ident *) node)->name;
|
|
|
|
if (clause == GROUP_CLAUSE)
|
|
{
|
|
|
|
/*
|
|
* In GROUP BY, we must prefer a match against a FROM-clause
|
|
* column to one against the targetlist. Look to see if there
|
|
* is a matching column. If so, fall through to let
|
|
* transformExpr() do the rest. NOTE: if name could refer
|
|
* ambiguously to more than one column name exposed by FROM,
|
|
* colnameToVar will elog(ERROR). That's just what
|
|
* we want here.
|
|
*/
|
|
if (colnameToVar(pstate, name) != NULL)
|
|
name = NULL;
|
|
}
|
|
|
|
if (name != NULL)
|
|
{
|
|
foreach(tl, tlist)
|
|
{
|
|
TargetEntry *tle = (TargetEntry *) lfirst(tl);
|
|
Resdom *resnode = tle->resdom;
|
|
|
|
if (!resnode->resjunk &&
|
|
strcmp(resnode->resname, name) == 0)
|
|
{
|
|
if (target_result != NULL)
|
|
{
|
|
if (!equal(target_result->expr, tle->expr))
|
|
elog(ERROR, "%s '%s' is ambiguous",
|
|
clauseText[clause], name);
|
|
}
|
|
else
|
|
target_result = tle;
|
|
/* Stay in loop to check for ambiguity */
|
|
}
|
|
}
|
|
if (target_result != NULL)
|
|
return target_result; /* return the first match */
|
|
}
|
|
}
|
|
if (IsA(node, A_Const))
|
|
{
|
|
Value *val = &((A_Const *) node)->val;
|
|
int targetlist_pos = 0;
|
|
int target_pos;
|
|
|
|
if (!IsA(val, Integer))
|
|
elog(ERROR, "Non-integer constant in %s", clauseText[clause]);
|
|
target_pos = intVal(val);
|
|
foreach(tl, tlist)
|
|
{
|
|
TargetEntry *tle = (TargetEntry *) lfirst(tl);
|
|
Resdom *resnode = tle->resdom;
|
|
|
|
if (!resnode->resjunk)
|
|
{
|
|
if (++targetlist_pos == target_pos)
|
|
return tle; /* return the unique match */
|
|
}
|
|
}
|
|
elog(ERROR, "%s position %d is not in target list",
|
|
clauseText[clause], target_pos);
|
|
}
|
|
|
|
/*
|
|
* Otherwise, we have an expression (this is a Postgres extension not
|
|
* found in SQL92). Convert the untransformed node to a transformed
|
|
* expression, and search for a match in the tlist. NOTE: it doesn't
|
|
* really matter whether there is more than one match. Also, we are
|
|
* willing to match a resjunk target here, though the above cases must
|
|
* ignore resjunk targets.
|
|
*/
|
|
expr = transformExpr(pstate, node, EXPR_COLUMN_FIRST);
|
|
|
|
foreach(tl, tlist)
|
|
{
|
|
TargetEntry *tle = (TargetEntry *) lfirst(tl);
|
|
|
|
if (equal(expr, tle->expr))
|
|
return tle;
|
|
}
|
|
|
|
/*
|
|
* If no matches, construct a new target entry which is appended to
|
|
* the end of the target list. This target is given resjunk = TRUE so
|
|
* that it will not be projected into the final tuple.
|
|
*/
|
|
target_result = transformTargetEntry(pstate, node, expr, NULL, true);
|
|
lappend(tlist, target_result);
|
|
|
|
return target_result;
|
|
}
|
|
|
|
|
|
/*
|
|
* transformGroupClause -
|
|
* transform a Group By clause
|
|
*
|
|
*/
|
|
List *
|
|
transformGroupClause(ParseState *pstate, List *grouplist, List *targetlist)
|
|
{
|
|
List *glist = NIL,
|
|
*gl;
|
|
|
|
foreach(gl, grouplist)
|
|
{
|
|
TargetEntry *tle;
|
|
|
|
tle = findTargetlistEntry(pstate, lfirst(gl),
|
|
targetlist, GROUP_CLAUSE);
|
|
|
|
/* avoid making duplicate grouplist entries */
|
|
if (!exprIsInSortList(tle->expr, glist, targetlist))
|
|
{
|
|
GroupClause *grpcl = makeNode(GroupClause);
|
|
|
|
grpcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
|
|
|
|
grpcl->sortop = any_ordering_op(tle->resdom->restype);
|
|
|
|
glist = lappend(glist, grpcl);
|
|
}
|
|
}
|
|
|
|
return glist;
|
|
}
|
|
|
|
/*
|
|
* transformSortClause -
|
|
* transform an ORDER BY clause
|
|
*/
|
|
List *
|
|
transformSortClause(ParseState *pstate,
|
|
List *orderlist,
|
|
List *targetlist)
|
|
{
|
|
List *sortlist = NIL;
|
|
List *olitem;
|
|
|
|
foreach(olitem, orderlist)
|
|
{
|
|
SortGroupBy *sortby = lfirst(olitem);
|
|
TargetEntry *tle;
|
|
|
|
tle = findTargetlistEntry(pstate, sortby->node,
|
|
targetlist, ORDER_CLAUSE);
|
|
|
|
sortlist = addTargetToSortList(tle, sortlist, targetlist,
|
|
sortby->useOp);
|
|
}
|
|
|
|
return sortlist;
|
|
}
|
|
|
|
/*
|
|
* transformDistinctClause -
|
|
* transform a DISTINCT or DISTINCT ON clause
|
|
*
|
|
* Since we may need to add items to the query's sortClause list, that list
|
|
* is passed by reference. We might also need to add items to the query's
|
|
* targetlist, but we assume that cannot be empty initially, so we can
|
|
* lappend to it even though the pointer is passed by value.
|
|
*/
|
|
List *
|
|
transformDistinctClause(ParseState *pstate, List *distinctlist,
|
|
List *targetlist, List **sortClause)
|
|
{
|
|
List *result = NIL;
|
|
List *slitem;
|
|
List *dlitem;
|
|
|
|
/* No work if there was no DISTINCT clause */
|
|
if (distinctlist == NIL)
|
|
return NIL;
|
|
|
|
if (lfirst(distinctlist) == NIL)
|
|
{
|
|
/* We had SELECT DISTINCT */
|
|
|
|
/*
|
|
* All non-resjunk elements from target list that are not already
|
|
* in the sort list should be added to it. (We don't really care
|
|
* what order the DISTINCT fields are checked in, so we can leave
|
|
* the user's ORDER BY spec alone, and just add additional sort
|
|
* keys to it to ensure that all targetlist items get sorted.)
|
|
*/
|
|
*sortClause = addAllTargetsToSortList(*sortClause, targetlist);
|
|
|
|
/*
|
|
* Now, DISTINCT list consists of all non-resjunk sortlist items.
|
|
* Actually, all the sortlist items had better be non-resjunk!
|
|
* Otherwise, user wrote SELECT DISTINCT with an ORDER BY item
|
|
* that does not appear anywhere in the SELECT targetlist, and we
|
|
* can't implement that with only one sorting pass...
|
|
*/
|
|
foreach(slitem, *sortClause)
|
|
{
|
|
SortClause *scl = (SortClause *) lfirst(slitem);
|
|
TargetEntry *tle = get_sortgroupclause_tle(scl, targetlist);
|
|
|
|
if (tle->resdom->resjunk)
|
|
elog(ERROR, "For SELECT DISTINCT, ORDER BY expressions must appear in target list");
|
|
else
|
|
result = lappend(result, copyObject(scl));
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* We had SELECT DISTINCT ON (expr, ...) */
|
|
|
|
/*
|
|
* If the user writes both DISTINCT ON and ORDER BY, then the two
|
|
* expression lists must match (until one or the other runs out).
|
|
* Otherwise the ORDER BY requires a different sort order than the
|
|
* DISTINCT does, and we can't implement that with only one sort
|
|
* pass (and if we do two passes, the results will be rather
|
|
* unpredictable). However, it's OK to have more DISTINCT ON
|
|
* expressions than ORDER BY expressions; we can just add the
|
|
* extra DISTINCT values to the sort list, much as we did above
|
|
* for ordinary DISTINCT fields.
|
|
*
|
|
* Actually, it'd be OK for the common prefixes of the two lists to
|
|
* match in any order, but implementing that check seems like more
|
|
* trouble than it's worth.
|
|
*/
|
|
List *nextsortlist = *sortClause;
|
|
|
|
foreach(dlitem, distinctlist)
|
|
{
|
|
TargetEntry *tle;
|
|
|
|
tle = findTargetlistEntry(pstate, lfirst(dlitem),
|
|
targetlist, DISTINCT_ON_CLAUSE);
|
|
|
|
if (nextsortlist != NIL)
|
|
{
|
|
SortClause *scl = (SortClause *) lfirst(nextsortlist);
|
|
|
|
if (tle->resdom->ressortgroupref != scl->tleSortGroupRef)
|
|
elog(ERROR, "SELECT DISTINCT ON expressions must match initial ORDER BY expressions");
|
|
result = lappend(result, copyObject(scl));
|
|
nextsortlist = lnext(nextsortlist);
|
|
}
|
|
else
|
|
{
|
|
*sortClause = addTargetToSortList(tle, *sortClause,
|
|
targetlist, NULL);
|
|
|
|
/*
|
|
* Probably, the tle should always have been added at the
|
|
* end of the sort list ... but search to be safe.
|
|
*/
|
|
foreach(slitem, *sortClause)
|
|
{
|
|
SortClause *scl = (SortClause *) lfirst(slitem);
|
|
|
|
if (tle->resdom->ressortgroupref == scl->tleSortGroupRef)
|
|
{
|
|
result = lappend(result, copyObject(scl));
|
|
break;
|
|
}
|
|
}
|
|
if (slitem == NIL)
|
|
elog(ERROR, "transformDistinctClause: failed to add DISTINCT ON clause to target list");
|
|
}
|
|
}
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
/*
|
|
* addAllTargetsToSortList
|
|
* Make sure all non-resjunk targets in the targetlist are in the
|
|
* ORDER BY list, adding the not-yet-sorted ones to the end of the list.
|
|
* This is typically used to help implement SELECT DISTINCT.
|
|
*
|
|
* Returns the updated ORDER BY list.
|
|
*/
|
|
List *
|
|
addAllTargetsToSortList(List *sortlist, List *targetlist)
|
|
{
|
|
List *i;
|
|
|
|
foreach(i, targetlist)
|
|
{
|
|
TargetEntry *tle = (TargetEntry *) lfirst(i);
|
|
|
|
if (!tle->resdom->resjunk)
|
|
sortlist = addTargetToSortList(tle, sortlist, targetlist, NULL);
|
|
}
|
|
return sortlist;
|
|
}
|
|
|
|
/*
|
|
* addTargetToSortList
|
|
* If the given targetlist entry isn't already in the ORDER BY list,
|
|
* add it to the end of the list, using the sortop with given name
|
|
* or any available sort operator if opname == NULL.
|
|
*
|
|
* Returns the updated ORDER BY list.
|
|
*/
|
|
static List *
|
|
addTargetToSortList(TargetEntry *tle, List *sortlist, List *targetlist,
|
|
char *opname)
|
|
{
|
|
/* avoid making duplicate sortlist entries */
|
|
if (!exprIsInSortList(tle->expr, sortlist, targetlist))
|
|
{
|
|
SortClause *sortcl = makeNode(SortClause);
|
|
|
|
sortcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
|
|
|
|
if (opname)
|
|
sortcl->sortop = oper_oid(opname,
|
|
tle->resdom->restype,
|
|
tle->resdom->restype,
|
|
false);
|
|
else
|
|
sortcl->sortop = any_ordering_op(tle->resdom->restype);
|
|
|
|
sortlist = lappend(sortlist, sortcl);
|
|
}
|
|
return sortlist;
|
|
}
|
|
|
|
/*
|
|
* assignSortGroupRef
|
|
* Assign the targetentry an unused ressortgroupref, if it doesn't
|
|
* already have one. Return the assigned or pre-existing refnumber.
|
|
*
|
|
* 'tlist' is the targetlist containing (or to contain) the given targetentry.
|
|
*/
|
|
Index
|
|
assignSortGroupRef(TargetEntry *tle, List *tlist)
|
|
{
|
|
Index maxRef;
|
|
List *l;
|
|
|
|
if (tle->resdom->ressortgroupref) /* already has one? */
|
|
return tle->resdom->ressortgroupref;
|
|
|
|
/* easiest way to pick an unused refnumber: max used + 1 */
|
|
maxRef = 0;
|
|
foreach(l, tlist)
|
|
{
|
|
Index ref = ((TargetEntry *) lfirst(l))->resdom->ressortgroupref;
|
|
|
|
if (ref > maxRef)
|
|
maxRef = ref;
|
|
}
|
|
tle->resdom->ressortgroupref = maxRef + 1;
|
|
return tle->resdom->ressortgroupref;
|
|
}
|
|
|
|
/*
|
|
* exprIsInSortList
|
|
* Is the given expression already in the sortlist?
|
|
* Note we will say 'yes' if it is equal() to any sortlist item,
|
|
* even though that might be a different targetlist member.
|
|
*
|
|
* Works for both SortClause and GroupClause lists.
|
|
*/
|
|
static bool
|
|
exprIsInSortList(Node *expr, List *sortList, List *targetList)
|
|
{
|
|
List *i;
|
|
|
|
foreach(i, sortList)
|
|
{
|
|
SortClause *scl = (SortClause *) lfirst(i);
|
|
|
|
if (equal(expr, get_sortgroupclause_expr(scl, targetList)))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|