/*------------------------------------------------------------------------- * * parse_clause.c * handle clauses in parser * * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.113 2003/04/29 22:13:10 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "catalog/heap.h" #include "nodes/makefuncs.h" #include "optimizer/clauses.h" #include "optimizer/tlist.h" #include "optimizer/var.h" #include "parser/analyze.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" #include "utils/builtins.h" #include "utils/guc.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 extractRemainingColumns(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 RangeTblRef *transformRangeFunction(ParseState *pstate, RangeFunction *r); static Node *transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels); static Node *buildMergedJoinVar(ParseState *pstate, JoinType jointype, Var *l_colvar, Var *r_colvar); static TargetEntry *findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause); static List *addTargetToSortList(TargetEntry *tle, List *sortlist, List *targetlist, List *opname); /* * transformFromClause - * Process the FROM clause and add items to the query's range table, * joinlist, and namespace. * * Note: we assume that pstate's p_rtable, p_joinlist, and p_namespace lists * were initialized to NIL when the pstate was created. We will add onto * any entries already present --- this is needed for rule processing, as * well as for UPDATE and DELETE. * * The range table may grow still further when we transform the expressions * in the query's quals and target list. (This is possible because in * POSTQUEL, we allowed references to relations not specified in the * from-clause. PostgreSQL keeps this extension to standard SQL.) */ void transformFromClause(ParseState *pstate, List *frmList) { List *fl; /* * The grammar will have produced a list of RangeVars, * RangeSubselects, RangeFunctions, and/or JoinExprs. Transform each * one (possibly adding entries to the rtable), check for duplicate * refnames, and then add it to the joinlist and namespace. */ foreach(fl, frmList) { Node *n = lfirst(fl); List *containedRels; n = transformFromClauseItem(pstate, n, &containedRels); checkNameSpaceConflicts(pstate, (Node *) pstate->p_namespace, n); pstate->p_joinlist = lappend(pstate->p_joinlist, n); pstate->p_namespace = lappend(pstate->p_namespace, n); } } /* * setTargetTable * Add the target relation of INSERT/UPDATE/DELETE to the range table, * and make the special links to it in the ParseState. * * We also open the target relation and acquire a write lock on it. * This must be done before processing the FROM list, in case the target * is also mentioned as a source relation --- we want to be sure to grab * the write lock before any read lock. * * If alsoSource is true, add the target to the query's joinlist and * namespace. 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. (NOTE: we do not bother * to check for namespace conflict; we assume that the namespace was * initially empty in these cases.) * * Returns the rangetable index of the target relation. */ int setTargetTable(ParseState *pstate, RangeVar *relation, bool inh, bool alsoSource) { RangeTblEntry *rte; int rtindex; /* Close old target; this could only happen for multi-action rules */ if (pstate->p_target_relation != NULL) heap_close(pstate->p_target_relation, NoLock); /* * Open target rel and grab suitable lock (which we will hold till end * of transaction). * * analyze.c will eventually do the corresponding heap_close(), but *not* * release the lock. */ pstate->p_target_relation = heap_openrv(relation, RowExclusiveLock); /* * Now build an RTE. */ rte = addRangeTableEntry(pstate, relation, NULL, inh, false); pstate->p_target_rangetblentry = rte; /* assume new rte is at end */ rtindex = length(pstate->p_rtable); Assert(rte == rt_fetch(rtindex, pstate->p_rtable)); /* * Override addRangeTableEntry's default checkForRead, and instead * mark target table as requiring write access. * * 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; rte->checkForWrite = true; /* * If UPDATE/DELETE, add table to joinlist and namespace. */ if (alsoSource) addRTEtoQuery(pstate, rte, true, true); return rtindex; } /* * Simplify InhOption (yes/no/default) into boolean yes/no. * * The reason we do things this way is that we don't want to examine the * SQL_inheritance option flag until parse_analyze is run. Otherwise, * we'd do the wrong thing with query strings that intermix SET commands * with queries. */ bool interpretInhOption(InhOption inhOpt) { switch (inhOpt) { case INH_NO: return false; case INH_YES: return true; case INH_DEFAULT: return SQL_inheritance; } elog(ERROR, "Bogus InhOption value"); return false; /* keep compiler quiet */ } /* * Extract all not-in-common columns from column lists of a source table */ static void extractRemainingColumns(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 = makeSimpleA_Expr(AEXPR_OP, "=", copyObject(lvar), copyObject(rvar)); if (result == NULL) result = (Node *) e; else { A_Expr *a; a = makeA_Expr(AEXPR_AND, NIL, result, (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); result = coerce_to_boolean(pstate, result, "JOIN/USING"); 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 *save_namespace; Relids clause_varnos; int varno; /* * This is a tad tricky, for two reasons. First, the namespace that * the join expression should see is just the two subtrees of the JOIN * plus any outer references from upper pstate levels. So, * temporarily set this pstate's namespace accordingly. (We need not * check for refname conflicts, because transformFromClauseItem() * already did.) NOTE: this code is OK only because the ON clause * can't legally alter the namespace by causing implicit relation refs * to be added. */ save_namespace = pstate->p_namespace; pstate->p_namespace = makeList2(j->larg, j->rarg); /* This part is just like transformWhereClause() */ result = transformExpr(pstate, j->quals); result = coerce_to_boolean(pstate, result, "JOIN/ON"); pstate->p_namespace = save_namespace; /* * 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 namespace if it uses fully-qualified names. * So, grovel through the transformed clause and make sure there are * no bogus references. (Outer references are OK, and are ignored * here.) */ clause_varnos = pull_varnos(result); while ((varno = bms_first_member(clause_varnos)) >= 0) { 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->aliasname); } } bms_free(clause_varnos); return result; } /* * transformTableEntry --- transform a RangeVar (simple relation reference) */ static RangeTblRef * transformTableEntry(ParseState *pstate, RangeVar *r) { 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, r, r->alias, interpretInhOption(r->inhOpt), true); /* * We create a RangeTblRef, but we do not add it to the joinlist or * namespace; our caller must do that if appropriate. */ 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) { 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->alias == NULL) elog(ERROR, "sub-select in FROM must have an alias"); /* * Analyze and transform the subquery. */ parsetrees = parse_sub_analyze(r->subquery, pstate); /* * 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) elog(ERROR, "Subselect in FROM may not have SELECT INTO"); /* * The subquery cannot make use of any variables from FROM items created * earlier in the current query. Per SQL92, the scope of a FROM item * does not include other FROM items. Formerly we hacked the namespace * so that the other variables weren't even visible, but it seems more * useful to leave them visible and give a specific error message. * * XXX this will need further work to support SQL99's LATERAL() feature, * wherein such references would indeed be legal. * * We can skip groveling through the subquery if there's not anything * visible in the current query. Also note that outer references are OK. */ if (pstate->p_namespace) { if (contain_vars_of_level((Node *) query, 1)) elog(ERROR, "Subselect in FROM may not refer to other relations of same query level"); } /* * OK, build an RTE for the subquery. */ rte = addRangeTableEntryForSubquery(pstate, query, r->alias, true); /* * We create a RangeTblRef, but we do not add it to the joinlist or * namespace; our caller must do that if appropriate. */ 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; } /* * transformRangeFunction --- transform a function call appearing in FROM */ static RangeTblRef * transformRangeFunction(ParseState *pstate, RangeFunction *r) { Node *funcexpr; char *funcname; RangeTblEntry *rte; RangeTblRef *rtr; /* Get function name for possible use as alias */ Assert(IsA(r->funccallnode, FuncCall)); funcname = strVal(llast(((FuncCall *) r->funccallnode)->funcname)); /* * Transform the raw FuncCall node. */ funcexpr = transformExpr(pstate, r->funccallnode); /* * The function parameters cannot make use of any variables from other * FROM items. (Compare to transformRangeSubselect(); the coding is * different though because we didn't parse as a sub-select with its own * level of namespace.) * * XXX this will need further work to support SQL99's LATERAL() feature, * wherein such references would indeed be legal. */ if (pstate->p_namespace) { if (contain_vars_of_level(funcexpr, 0)) elog(ERROR, "FROM function expression may not refer to other relations of same query level"); } /* * Disallow aggregate functions in the expression. (No reason to * postpone this check until parseCheckAggregates.) */ if (pstate->p_hasAggs) { if (contain_agg_clause(funcexpr)) elog(ERROR, "cannot use aggregate function in FROM function expression"); } /* * If a coldeflist is supplied, ensure it defines a legal set of names * (no duplicates) and datatypes (no pseudo-types, for instance). */ if (r->coldeflist) { TupleDesc tupdesc; tupdesc = BuildDescForRelation(r->coldeflist); CheckAttributeNamesTypes(tupdesc, RELKIND_COMPOSITE_TYPE); } /* * OK, build an RTE for the function. */ rte = addRangeTableEntryForFunction(pstate, funcname, funcexpr, r, true); /* * We create a RangeTblRef, but we do not add it to the joinlist or * namespace; our caller must do that if appropriate. */ 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 and namespace. * 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 and join 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, RangeFunction)) { /* function is like a plain relation */ RangeTblRef *rtr; rtr = transformRangeFunction(pstate, (RangeFunction *) n); *containedRels = makeListi1(rtr->rtindex); return (Node *) rtr; } else if (IsA(n, JoinExpr)) { /* A newfangled join expression */ JoinExpr *j = (JoinExpr *) n; List *my_containedRels, *l_containedRels, *r_containedRels, *l_colnames, *r_colnames, *res_colnames, *l_colvars, *r_colvars, *res_colvars; Index leftrti, rightrti; RangeTblEntry *rte; /* * 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 for possible use by * transformJoinOnClause below. */ my_containedRels = nconc(l_containedRels, r_containedRels); /* * Check for conflicting refnames in left and right subtrees. Must * do this because higher levels will assume I hand back a self- * consistent namespace subtree. */ checkNameSpaceConflicts(pstate, j->larg, j->rarg); /* * Extract column name and var lists from both subtrees * * Note: expandRTE returns new lists, safe for me to modify */ if (IsA(j->larg, RangeTblRef)) leftrti = ((RangeTblRef *) j->larg)->rtindex; else if (IsA(j->larg, JoinExpr)) leftrti = ((JoinExpr *) j->larg)->rtindex; else { elog(ERROR, "transformFromClauseItem: unexpected subtree type"); leftrti = 0; /* keep compiler quiet */ } rte = rt_fetch(leftrti, pstate->p_rtable); expandRTE(pstate, rte, &l_colnames, &l_colvars); if (IsA(j->rarg, RangeTblRef)) rightrti = ((RangeTblRef *) j->rarg)->rtindex; else if (IsA(j->rarg, JoinExpr)) rightrti = ((JoinExpr *) j->rarg)->rtindex; else { elog(ERROR, "transformFromClauseItem: unexpected subtree type"); rightrti = 0; /* keep compiler quiet */ } rte = rt_fetch(rightrti, pstate->p_rtable); expandRTE(pstate, rte, &r_colnames, &r_colvars); /* * 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 merged 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; int ndx; int l_index = -1; int r_index = -1; Var *l_colvar, *r_colvar; /* Check for USING(foo,foo) */ foreach(col, res_colnames) { char *res_colname = strVal(lfirst(col)); if (strcmp(res_colname, u_colname) == 0) elog(ERROR, "USING column name \"%s\" appears more than once", u_colname); } /* Find it in left input */ 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); /* Find it in right input */ 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, lfirst(ucol)); res_colvars = lappend(res_colvars, buildMergedJoinVar(pstate, j->jointype, l_colvar, r_colvar)); } j->quals = transformJoinUsingClause(pstate, l_usingvars, r_usingvars); } else if (j->quals) { /* User-written ON-condition; transform it */ j->quals = transformJoinOnClause(pstate, j, my_containedRels); } else { /* CROSS JOIN: no quals */ } /* Add remaining columns from each side to the output columns */ extractRemainingColumns(res_colnames, l_colnames, l_colvars, &l_colnames, &l_colvars); extractRemainingColumns(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); /* * Check alias (AS clause), if any. */ if (j->alias) { if (j->alias->colnames != NIL) { if (length(j->alias->colnames) > length(res_colnames)) elog(ERROR, "Column alias list for \"%s\" has too many entries", j->alias->aliasname); } } /* * Now build an RTE for the result of the join */ rte = addRangeTableEntryForJoin(pstate, res_colnames, j->jointype, res_colvars, j->alias, true); /* assume new rte is at end */ j->rtindex = length(pstate->p_rtable); Assert(rte == rt_fetch(j->rtindex, pstate->p_rtable)); /* * Include join RTE in returned containedRels list */ *containedRels = lconsi(j->rtindex, my_containedRels); 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 */ } /* * buildMergedJoinVar - * generate a suitable replacement expression for a merged join column */ static Node * buildMergedJoinVar(ParseState *pstate, JoinType jointype, Var *l_colvar, Var *r_colvar) { Oid outcoltype; int32 outcoltypmod; Node *l_node, *r_node, *res_node; /* * Choose output type if input types are dissimilar. */ outcoltype = l_colvar->vartype; outcoltypmod = l_colvar->vartypmod; if (outcoltype != r_colvar->vartype) { outcoltype = select_common_type(makeListo2(l_colvar->vartype, r_colvar->vartype), "JOIN/USING"); outcoltypmod = -1; /* ie, unknown */ } else if (outcoltypmod != r_colvar->vartypmod) { /* same type, but not same typmod */ outcoltypmod = -1; /* ie, unknown */ } /* * Insert coercion functions if needed. Note that a difference in * typmod can only happen if input has typmod but outcoltypmod is -1. * In that case we insert a RelabelType to clearly mark that result's * typmod is not same as input. */ if (l_colvar->vartype != outcoltype) l_node = coerce_type(pstate, (Node *) l_colvar, l_colvar->vartype, outcoltype, COERCION_IMPLICIT, COERCE_IMPLICIT_CAST); else if (l_colvar->vartypmod != outcoltypmod) l_node = (Node *) makeRelabelType((Expr *) l_colvar, outcoltype, outcoltypmod, COERCE_IMPLICIT_CAST); else l_node = (Node *) l_colvar; if (r_colvar->vartype != outcoltype) r_node = coerce_type(pstate, (Node *) r_colvar, r_colvar->vartype, outcoltype, COERCION_IMPLICIT, COERCE_IMPLICIT_CAST); else if (r_colvar->vartypmod != outcoltypmod) r_node = (Node *) makeRelabelType((Expr *) r_colvar, outcoltype, outcoltypmod, COERCE_IMPLICIT_CAST); else r_node = (Node *) r_colvar; /* * Choose what to emit */ switch (jointype) { case JOIN_INNER: /* * We can use either var; prefer non-coerced one if available. */ if (IsA(l_node, Var)) res_node = l_node; else if (IsA(r_node, Var)) res_node = r_node; else res_node = l_node; break; case JOIN_LEFT: /* Always use left var */ res_node = l_node; break; case JOIN_RIGHT: /* Always use right var */ res_node = r_node; break; case JOIN_FULL: { /* * Here we must build a COALESCE expression to ensure that * the join output is non-null if either input is. */ CoalesceExpr *c = makeNode(CoalesceExpr); c->coalescetype = outcoltype; c->args = makeList2(l_node, r_node); res_node = (Node *) c; break; } default: elog(ERROR, "buildMergedJoinVar: unexpected jointype %d", (int) jointype); res_node = NULL; /* keep compiler quiet */ break; } return res_node; } /* * 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); qual = coerce_to_boolean(pstate, qual, "WHERE"); 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, ColumnRef) && length(((ColumnRef *) node)->fields) == 1 && ((ColumnRef *) node)->indirection == NIL) { char *name = strVal(lfirst(((ColumnRef *) node)->fields)); 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); 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 (!targetIsInSortList(tle, glist)) { GroupClause *grpcl = makeNode(GroupClause); grpcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist); grpcl->sortop = ordering_oper_opid(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, NIL); /* * 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, NIL); } 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 the default sort operator if opname == NIL. * * Returns the updated ORDER BY list. */ static List * addTargetToSortList(TargetEntry *tle, List *sortlist, List *targetlist, List *opname) { /* avoid making duplicate sortlist entries */ if (!targetIsInSortList(tle, sortlist)) { SortClause *sortcl = makeNode(SortClause); sortcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist); if (opname) sortcl->sortop = compatible_oper_opid(opname, tle->resdom->restype, tle->resdom->restype, false); else sortcl->sortop = ordering_oper_opid(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; } /* * targetIsInSortList * Is the given target item already in the sortlist? * * Works for both SortClause and GroupClause lists. Note that the main * reason we need this routine (and not just a quick test for nonzeroness * of ressortgroupref) is that a TLE might be in only one of the lists. */ bool targetIsInSortList(TargetEntry *tle, List *sortList) { Index ref = tle->resdom->ressortgroupref; List *i; /* no need to scan list if tle has no marker */ if (ref == 0) return false; foreach(i, sortList) { SortClause *scl = (SortClause *) lfirst(i); if (scl->tleSortGroupRef == ref) return true; } return false; }