/*------------------------------------------------------------------------- * * parse_clause.c * handle clauses in parser * * Portions Copyright (c) 1996-2000, PostgreSQL, Inc * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.68 2000/09/29 18:21:36 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "nodes/makefuncs.h" #include "optimizer/tlist.h" #include "optimizer/var.h" #include "parser/analyze.h" #include "parser/parse.h" #include "parser/parsetree.h" #include "parser/parse_clause.h" #include "parser/parse_coerce.h" #include "parser/parse_expr.h" #include "parser/parse_oper.h" #include "parser/parse_relation.h" #include "parser/parse_target.h" #include "parser/parse_type.h" #define ORDER_CLAUSE 0 #define GROUP_CLAUSE 1 #define DISTINCT_ON_CLAUSE 2 static char *clauseText[] = {"ORDER BY", "GROUP BY", "DISTINCT ON"}; static void extractUniqueColumns(List *common_colnames, List *src_colnames, List *src_colvars, List **res_colnames, List **res_colvars); static Node *transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars); static Node *transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *containedRels); static RangeTblRef *transformTableEntry(ParseState *pstate, RangeVar *r); static RangeTblRef *transformRangeSubselect(ParseState *pstate, RangeSubselect *r); static Node *transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels); static TargetEntry *findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause); static List *addTargetToSortList(TargetEntry *tle, List *sortlist, List *targetlist, char *opname); static bool exprIsInSortList(Node *expr, List *sortList, List *targetList); /* * makeRangeTable - * Build the initial range table from the FROM clause. * * The range table constructed here may grow as we transform the expressions * in the query's quals and target list. (Note that this happens because in * POSTQUEL, we allow references to relations not specified in the * from-clause. PostgreSQL keeps this extension to standard SQL.) * * Note: we assume that pstate's p_rtable and p_joinlist lists were * initialized to NIL when the pstate was created. We will add onto * any entries already present --- this is needed for rule processing! */ void makeRangeTable(ParseState *pstate, List *frmList) { List *fl; /* * The grammar will have produced a list of RangeVars, RangeSubselects, * and/or JoinExprs. Transform each one, and then add it to the joinlist. */ foreach(fl, frmList) { Node *n = lfirst(fl); List *containedRels; n = transformFromClauseItem(pstate, n, &containedRels); pstate->p_joinlist = lappend(pstate->p_joinlist, n); } } /* * setTargetTable * Add the target relation of INSERT/UPDATE/DELETE to the range table, * and make the special links to it in the ParseState. * * inJoinSet says whether to add the target to the join list. * For INSERT, we don't want the target to be joined to; it's a * destination of tuples, not a source. For UPDATE/DELETE, we do * need to scan or join the target. */ void setTargetTable(ParseState *pstate, char *relname, bool inh, bool inJoinSet) { RangeTblEntry *rte; /* look for relname only at current nesting level... */ if (refnameRangeTablePosn(pstate, relname, NULL) == 0) { rte = addRangeTableEntry(pstate, relname, NULL, inh, false); /* * Since the rel wasn't in the rangetable already, it's not being * read; override addRangeTableEntry's default checkForRead. * * If we find an explicit reference to the rel later during * parse analysis, scanRTEForColumn will change checkForRead * to 'true' again. That can't happen for INSERT but it is * possible for UPDATE and DELETE. */ rte->checkForRead = false; } else { rte = refnameRangeTableEntry(pstate, relname); /* * Since the rel was in the rangetable already, it's being read * as well as written. Therefore, leave checkForRead true. */ /* XXX what if pre-existing entry has wrong inh setting? */ } /* Mark target table as requiring write access. */ rte->checkForWrite = true; if (inJoinSet) addRTEtoJoinList(pstate, rte); /* This could only happen for multi-action rules */ if (pstate->p_target_relation != NULL) heap_close(pstate->p_target_relation, AccessShareLock); pstate->p_target_rangetblentry = rte; pstate->p_target_relation = heap_open(rte->relid, AccessShareLock); /* will close relation later, see analyze.c */ } /* * Extract all not-in-common columns from column lists of a source table */ static void extractUniqueColumns(List *common_colnames, List *src_colnames, List *src_colvars, List **res_colnames, List **res_colvars) { List *new_colnames = NIL; List *new_colvars = NIL; List *lnames, *lvars = src_colvars; foreach(lnames, src_colnames) { char *colname = strVal(lfirst(lnames)); bool match = false; List *cnames; foreach(cnames, common_colnames) { char *ccolname = strVal(lfirst(cnames)); if (strcmp(colname, ccolname) == 0) { match = true; break; } } if (!match) { new_colnames = lappend(new_colnames, lfirst(lnames)); new_colvars = lappend(new_colvars, lfirst(lvars)); } lvars = lnext(lvars); } *res_colnames = new_colnames; *res_colvars = new_colvars; } /* transformJoinUsingClause() * Build a complete ON clause from a partially-transformed USING list. * We are given lists of nodes representing left and right match columns. * Result is a transformed qualification expression. */ static Node * transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars) { Node *result = NULL; List *lvars, *rvars = rightVars; /* * We cheat a little bit here by building an untransformed operator * tree whose leaves are the already-transformed Vars. This is OK * because transformExpr() won't complain about already-transformed * subnodes. */ foreach(lvars, leftVars) { Node *lvar = (Node *) lfirst(lvars); Node *rvar = (Node *) lfirst(rvars); A_Expr *e; e = makeNode(A_Expr); e->oper = OP; e->opname = "="; e->lexpr = copyObject(lvar); e->rexpr = copyObject(rvar); if (result == NULL) result = (Node *) e; else { A_Expr *a = makeNode(A_Expr); a->oper = AND; a->opname = NULL; a->lexpr = result; a->rexpr = (Node *) e; result = (Node *) a; } rvars = lnext(rvars); } /* * Since the references are already Vars, and are certainly from the * input relations, we don't have to go through the same pushups that * transformJoinOnClause() does. Just invoke transformExpr() to fix * up the operators, and we're done. */ result = transformExpr(pstate, result, EXPR_COLUMN_FIRST); if (exprType(result) != BOOLOID) { /* This could only happen if someone defines a funny version of '=' */ elog(ERROR, "JOIN/USING clause must return type bool, not type %s", typeidTypeName(exprType(result))); } return result; } /* transformJoinUsingClause() */ /* transformJoinOnClause() * Transform the qual conditions for JOIN/ON. * Result is a transformed qualification expression. */ static Node * transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *containedRels) { Node *result; List *sv_joinlist; List *clause_varnos, *l; /* * This is a tad tricky, for two reasons. First, at the point where * we're called, the two subtrees of the JOIN node aren't yet part of * the pstate's joinlist, which means that transformExpr() won't resolve * unqualified references to their columns correctly. We fix this in a * slightly klugy way: temporarily make the pstate's joinlist consist of * just those two subtrees (which creates exactly the namespace the ON * clause should see). This is OK only because the ON clause can't * legally alter the joinlist by causing relation refs to be added. */ sv_joinlist = pstate->p_joinlist; pstate->p_joinlist = makeList2(j->larg, j->rarg); /* This part is just like transformWhereClause() */ result = transformExpr(pstate, j->quals, EXPR_COLUMN_FIRST); if (exprType(result) != BOOLOID) { elog(ERROR, "JOIN/ON clause must return type bool, not type %s", typeidTypeName(exprType(result))); } pstate->p_joinlist = sv_joinlist; /* * Second, we need to check that the ON condition doesn't refer to any * rels outside the input subtrees of the JOIN. It could do that despite * our hack on the joinlist if it uses fully-qualified names. So, grovel * through the transformed clause and make sure there are no bogus * references. */ clause_varnos = pull_varnos(result); foreach(l, clause_varnos) { int varno = lfirsti(l); if (! intMember(varno, containedRels)) { elog(ERROR, "JOIN/ON clause refers to \"%s\", which is not part of JOIN", rt_fetch(varno, pstate->p_rtable)->eref->relname); } } freeList(clause_varnos); return result; } /* * transformTableEntry --- transform a RangeVar (simple relation reference) */ static RangeTblRef * transformTableEntry(ParseState *pstate, RangeVar *r) { char *relname = r->relname; RangeTblEntry *rte; RangeTblRef *rtr; /* * mark this entry to indicate it comes from the FROM clause. In SQL, * the target list can only refer to range variables specified in the * from clause but we follow the more powerful POSTQUEL semantics and * automatically generate the range variable if not specified. However * there are times we need to know whether the entries are legitimate. */ rte = addRangeTableEntry(pstate, relname, r->name, r->inh, true); /* * We create a RangeTblRef, but we do not add it to the joinlist here. * makeRangeTable will do so, if we are at top level of the FROM clause. */ rtr = makeNode(RangeTblRef); /* assume new rte is at end */ rtr->rtindex = length(pstate->p_rtable); Assert(rte == rt_fetch(rtr->rtindex, pstate->p_rtable)); return rtr; } /* * transformRangeSubselect --- transform a sub-SELECT appearing in FROM */ static RangeTblRef * transformRangeSubselect(ParseState *pstate, RangeSubselect *r) { SelectStmt *subquery = (SelectStmt *) r->subquery; List *parsetrees; Query *query; RangeTblEntry *rte; RangeTblRef *rtr; /* * We require user to supply an alias for a subselect, per SQL92. * To relax this, we'd have to be prepared to gin up a unique alias * for an unlabeled subselect. */ if (r->name == NULL) elog(ERROR, "sub-select in FROM must have an alias"); /* * subquery node might not be SelectStmt if user wrote something like * FROM (SELECT ... UNION SELECT ...). Our current implementation of * UNION/INTERSECT/EXCEPT is too messy to deal with here, so punt until * we redesign querytrees to make it more reasonable. */ if (subquery == NULL || !IsA(subquery, SelectStmt)) elog(ERROR, "Set operations not yet supported in subselects in FROM"); /* * Analyze and transform the subquery as if it were an independent * statement (we do NOT want it to see the outer query as a parent). */ parsetrees = parse_analyze(makeList1(subquery), NULL); /* * Check that we got something reasonable. Some of these conditions * are probably impossible given restrictions of the grammar, but * check 'em anyway. */ if (length(parsetrees) != 1) elog(ERROR, "Unexpected parse analysis result for subselect in FROM"); query = (Query *) lfirst(parsetrees); if (query == NULL || !IsA(query, Query)) elog(ERROR, "Unexpected parse analysis result for subselect in FROM"); if (query->commandType != CMD_SELECT) elog(ERROR, "Expected SELECT query from subselect in FROM"); if (query->resultRelation != 0 || query->into != NULL || query->isPortal) elog(ERROR, "Subselect in FROM may not have SELECT INTO"); /* * OK, build an RTE for the subquery. */ rte = addRangeTableEntryForSubquery(pstate, query, r->name, true); /* * We create a RangeTblRef, but we do not add it to the joinlist here. * makeRangeTable will do so, if we are at top level of the FROM clause. */ rtr = makeNode(RangeTblRef); /* assume new rte is at end */ rtr->rtindex = length(pstate->p_rtable); Assert(rte == rt_fetch(rtr->rtindex, pstate->p_rtable)); return rtr; } /* * transformFromClauseItem - * Transform a FROM-clause item, adding any required entries to the * range table list being built in the ParseState, and return the * transformed item ready to include in the joinlist. * This routine can recurse to handle SQL92 JOIN expressions. * * Aside from the primary return value (the transformed joinlist item) * this routine also returns an integer list of the rangetable indexes * of all the base relations represented in the joinlist item. This * list is needed for checking JOIN/ON conditions in higher levels. */ static Node * transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels) { if (IsA(n, RangeVar)) { /* Plain relation reference */ RangeTblRef *rtr; rtr = transformTableEntry(pstate, (RangeVar *) n); *containedRels = makeListi1(rtr->rtindex); return (Node *) rtr; } else if (IsA(n, RangeSubselect)) { /* sub-SELECT is like a plain relation */ RangeTblRef *rtr; rtr = transformRangeSubselect(pstate, (RangeSubselect *) n); *containedRels = makeListi1(rtr->rtindex); return (Node *) rtr; } else if (IsA(n, JoinExpr)) { /* A newfangled join expression */ JoinExpr *j = (JoinExpr *) n; List *l_containedRels, *r_containedRels, *l_colnames, *r_colnames, *res_colnames, *l_colvars, *r_colvars, *res_colvars; /* * Recursively process the left and right subtrees */ j->larg = transformFromClauseItem(pstate, j->larg, &l_containedRels); j->rarg = transformFromClauseItem(pstate, j->rarg, &r_containedRels); /* * Generate combined list of relation indexes */ *containedRels = nconc(l_containedRels, r_containedRels); /* * Extract column name and var lists from both subtrees */ if (IsA(j->larg, JoinExpr)) { /* 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 = oprid(oper("<", tle->resdom->restype, tle->resdom->restype, false)); 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 = oprid(oper(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; } /* transformUnionClause() * Transform a UNION clause. * Note that the union clause is actually a fully-formed select structure. * So, it is evaluated as a select, then the resulting target fields * are matched up to ensure correct types in the results. * The select clause parsing is done recursively, so the unions are evaluated * right-to-left. One might want to look at all columns from all clauses before * trying to coerce, but unless we keep track of the call depth we won't know * when to do this because of the recursion. * Let's just try matching in pairs for now (right to left) and see if it works. * - thomas 1998-05-22 */ #ifdef NOT_USED static List * transformUnionClause(List *unionClause, List *targetlist) { List *union_list = NIL; List *qlist, *qlist_item; if (unionClause) { /* recursion */ qlist = parse_analyze(unionClause, NULL); foreach(qlist_item, qlist) { Query *query = (Query *) lfirst(qlist_item); List *prev_target = targetlist; List *next_target; int prev_len = 0, next_len = 0; foreach(prev_target, targetlist) if (!((TargetEntry *) lfirst(prev_target))->resdom->resjunk) prev_len++; foreach(next_target, query->targetList) if (!((TargetEntry *) lfirst(next_target))->resdom->resjunk) next_len++; if (prev_len != next_len) elog(ERROR, "Each UNION clause must have the same number of columns"); foreach(next_target, query->targetList) { Oid itype; Oid otype; otype = ((TargetEntry *) lfirst(prev_target))->resdom->restype; itype = ((TargetEntry *) lfirst(next_target))->resdom->restype; /* one or both is a NULL column? then don't convert... */ if (otype == InvalidOid) { /* propagate a known type forward, if available */ if (itype != InvalidOid) ((TargetEntry *) lfirst(prev_target))->resdom->restype = itype; #if FALSE else { ((TargetEntry *) lfirst(prev_target))->resdom->restype = UNKNOWNOID; ((TargetEntry *) lfirst(next_target))->resdom->restype = UNKNOWNOID; } #endif } else if (itype == InvalidOid) { } /* they don't match in type? then convert... */ else if (itype != otype) { Node *expr; expr = ((TargetEntry *) lfirst(next_target))->expr; expr = CoerceTargetExpr(NULL, expr, itype, otype, -1); if (expr == NULL) { elog(ERROR, "Unable to transform %s to %s" "\n\tEach UNION clause must have compatible target types", typeidTypeName(itype), typeidTypeName(otype)); } ((TargetEntry *) lfirst(next_target))->expr = expr; ((TargetEntry *) lfirst(next_target))->resdom->restype = otype; } /* both are UNKNOWN? then evaluate as text... */ else if (itype == UNKNOWNOID) { ((TargetEntry *) lfirst(next_target))->resdom->restype = TEXTOID; ((TargetEntry *) lfirst(prev_target))->resdom->restype = TEXTOID; } prev_target = lnext(prev_target); } union_list = lappend(union_list, query); } return union_list; } else return NIL; } #endif