From 350cb386af0d5caf5ae32781e80b8622fb5e4fe1 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 24 Dec 1999 06:43:34 +0000 Subject: [PATCH] Clean up handling of explicit NULL constants. Cases like SELECT null::text; SELECT int4fac(null); work as expected now. In some cases a NULL must be surrounded by parentheses: SELECT 2 + null; fails SELECT 2 + (null); OK This is a grammatical ambiguity that seems difficult to avoid. Other than that, NULLs seem to behave about like you'd expect. The internal implementation is that NULL constants are typed as UNKNOWN (like untyped string constants) until the parser can deduce the right type. --- src/backend/nodes/equalfuncs.c | 9 +++++- src/backend/parser/parse_expr.c | 50 +++++++++++++++++-------------- src/backend/parser/parse_node.c | 30 +++++++++++-------- src/backend/utils/adt/ruleutils.c | 21 ++++++++----- 4 files changed, 67 insertions(+), 43 deletions(-) diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c index f70fe508ae..cc23555c46 100644 --- a/src/backend/nodes/equalfuncs.c +++ b/src/backend/nodes/equalfuncs.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.53 1999/12/13 01:26:53 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.54 1999/12/24 06:43:32 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -144,6 +144,13 @@ _equalConst(Const *a, Const *b) if (a->constbyval != b->constbyval) return false; /* XXX What about constisset and constiscast? */ + /* + * We treat all NULL constants of the same type as equal. + * Someday this might need to change? But datumIsEqual + * doesn't work on nulls, so... + */ + if (a->constisnull) + return true; return (datumIsEqual(a->constvalue, b->constvalue, a->consttype, a->constbyval, a->constlen)); } diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c index 0b738a8730..dab7161c04 100644 --- a/src/backend/parser/parse_expr.c +++ b/src/backend/parser/parse_expr.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.62 1999/12/17 01:25:25 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.63 1999/12/24 06:43:33 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -353,7 +353,7 @@ transformExpr(ParseState *pstate, Node *expr, int precedence) n->val.type = T_Null; c->defresult = (Node *) n; } - c->defresult = transformExpr(pstate, (Node *) c->defresult, precedence); + c->defresult = transformExpr(pstate, c->defresult, precedence); /* now check types across result clauses... */ c->casetype = exprType(c->defresult); @@ -369,32 +369,30 @@ transformExpr(ParseState *pstate, Node *expr, int precedence) if (wtype && (wtype != UNKNOWNOID) && (wtype != ptype)) { - /* so far, only nulls so take anything... */ - if (!ptype) + if (!ptype || ptype == UNKNOWNOID) { + /* so far, only nulls so take anything... */ ptype = wtype; pcategory = TypeCategory(ptype); } - - /* - * both types in different categories? then not - * much hope... - */ else if ((TypeCategory(wtype) != pcategory) || ((TypeCategory(wtype) == USER_TYPE) && (TypeCategory(c->casetype) == USER_TYPE))) { + /* + * both types in different categories? + * then not much hope... + */ elog(ERROR, "CASE/WHEN types '%s' and '%s' not matched", typeidTypeName(c->casetype), typeidTypeName(wtype)); } - - /* - * new one is preferred and can convert? then take - * it... - */ else if (IsPreferredType(pcategory, wtype) && can_coerce_type(1, &ptype, &wtype)) { + /* + * new one is preferred and can convert? + * then take it... + */ ptype = wtype; pcategory = TypeCategory(ptype); } @@ -404,9 +402,8 @@ transformExpr(ParseState *pstate, Node *expr, int precedence) /* Convert default result clause, if necessary */ if (c->casetype != ptype) { - if (!c->casetype) + if (!c->casetype || c->casetype == UNKNOWNOID) { - /* * default clause is NULL, so assign preferred * type from WHEN clauses... @@ -694,11 +691,12 @@ exprTypmod(Node *expr) static Node * parser_typecast(Value *expr, TypeName *typename, int32 atttypmod) { - Const *adt; - Datum lcp; + Const *con; Type tp; + Datum datum; char *const_string = NULL; bool string_palloced = false; + bool isNull = false; switch (nodeTag(expr)) { @@ -713,6 +711,9 @@ parser_typecast(Value *expr, TypeName *typename, int32 atttypmod) string_palloced = true; const_string = float8out(&expr->val.dval); break; + case T_Null: + isNull = true; + break; default: elog(ERROR, "parser_typecast: cannot cast this expression to type '%s'", @@ -729,12 +730,15 @@ parser_typecast(Value *expr, TypeName *typename, int32 atttypmod) else tp = (Type) typenameType(typename->name); - lcp = stringTypeDatum(tp, const_string, atttypmod); + if (isNull) + datum = (Datum) NULL; + else + datum = stringTypeDatum(tp, const_string, atttypmod); - adt = makeConst(typeTypeId(tp), + con = makeConst(typeTypeId(tp), typeLen(tp), - (Datum) lcp, - false, + datum, + isNull, typeByVal(tp), false, /* not a set */ true /* is cast */ ); @@ -742,5 +746,5 @@ parser_typecast(Value *expr, TypeName *typename, int32 atttypmod) if (string_palloced) pfree(const_string); - return (Node *) adt; + return (Node *) con; } diff --git a/src/backend/parser/parse_node.c b/src/backend/parser/parse_node.c index 2cab730412..c660df3826 100644 --- a/src/backend/parser/parse_node.c +++ b/src/backend/parser/parse_node.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/parser/parse_node.c,v 1.33 1999/11/22 17:56:21 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/parser/parse_node.c,v 1.34 1999/12/24 06:43:33 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -61,28 +61,27 @@ make_operand(char *opname, Oid target_typeId) { Node *result; - Type target_type; + Type target_type = typeidType(target_typeId); if (tree != NULL) { - result = tree; - target_type = typeidType(target_typeId); - disallow_setop(opname, target_type, result); - + disallow_setop(opname, target_type, tree); /* must coerce? */ if (target_typeId != orig_typeId) result = coerce_type(NULL, tree, orig_typeId, target_typeId, -1); + else + result = tree; } - /* otherwise, this is a NULL value */ else { + /* otherwise, this is a NULL value */ Const *con = makeNode(Const); con->consttype = target_typeId; - con->constlen = 0; - con->constvalue = (Datum) (struct varlena *) NULL; + con->constlen = typeLen(target_type); + con->constvalue = (Datum) NULL; con->constisnull = true; - con->constbyval = true; + con->constbyval = typeByVal(target_type); con->constisset = false; result = (Node *) con; } @@ -394,7 +393,8 @@ transformArraySubscripts(ParseState *pstate, * of the "natural" type for the constant. For strings we produce * a constant of type UNKNOWN ---- representation is the same as text, * but this indicates to later type resolution that we're not sure that - * it should be considered text. + * it should be considered text. Explicit "NULL" constants are also + * typed as UNKNOWN. */ Const * make_const(Value *value) @@ -444,7 +444,13 @@ make_const(Value *value) elog(NOTICE, "make_const: unknown type %d\n", nodeTag(value)); /* return a null const */ - con = makeConst(0, 0, (Datum) NULL, true, false, false, false); + con = makeConst(UNKNOWNOID, + -1, + (Datum) NULL, + true, + false, + false, + false); return con; } diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c index 47fd957c99..00099791c0 100644 --- a/src/backend/utils/adt/ruleutils.c +++ b/src/backend/utils/adt/ruleutils.c @@ -3,7 +3,7 @@ * out of it's tuple * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.35 1999/12/13 01:27:01 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.36 1999/12/24 06:43:34 tgl Exp $ * * This software is copyrighted by Jan Wieck - Hamburg. * @@ -1606,12 +1606,6 @@ get_const_expr(Const *constval, deparse_context *context) char *valptr; bool isnull = FALSE; - if (constval->constisnull) - { - appendStringInfo(buf, "NULL"); - return; - } - typetup = SearchSysCacheTuple(TYPEOID, ObjectIdGetDatum(constval->consttype), 0, 0, 0); @@ -1620,6 +1614,19 @@ get_const_expr(Const *constval, deparse_context *context) typeStruct = (Form_pg_type) GETSTRUCT(typetup); + if (constval->constisnull) + { + /* + * Always label the type of a NULL constant. This not only + * prevents misdecisions about the type, but it ensures that + * our output is a valid b_expr. + */ + extval = pstrdup(NameStr(typeStruct->typname)); + appendStringInfo(buf, "NULL::%s", quote_identifier(extval)); + pfree(extval); + return; + } + fmgr_info(typeStruct->typoutput, &finfo_output); extval = (char *) (*fmgr_faddr(&finfo_output)) (constval->constvalue, &isnull, -1);