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Commit7173c48

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Fix exprTypmod to recognize length-coercion function expressions,
such as bpchar(char_expression, N), and pull out the attrtypmod thatthe function is coercing to. This allows correct deduction of thecolumn type in examples such asCREATE VIEW v AS SELECT f1::char(8) FROM tbl;Formerly we labeled v's column as char-of-unknown-length not char(8).Also, this change causes the parser not to insert a redundant lengthcoercion function if the user has explicitly casted an INSERT or UPDATEexpression to the right length.
1 parentcbf4c96 commit7173c48

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2 files changed

+105
-2
lines changed

2 files changed

+105
-2
lines changed

‎src/backend/parser/parse_expr.c‎

Lines changed: 103 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,14 +8,15 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.70 2000/02/21 18:47:02 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.71 2000/02/26 21:11:10 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
1515

1616
#include"postgres.h"
1717

1818
#include"catalog/pg_operator.h"
19+
#include"catalog/pg_proc.h"
1920
#include"nodes/makefuncs.h"
2021
#include"nodes/params.h"
2122
#include"nodes/relation.h"
@@ -29,6 +30,7 @@
2930
#include"parser/parse_relation.h"
3031
#include"parser/parse_target.h"
3132
#include"utils/builtins.h"
33+
#include"utils/syscache.h"
3234

3335
staticNode*parser_typecast_constant(Value*expr,TypeName*typename);
3436
staticNode*parser_typecast_expression(ParseState*pstate,
@@ -701,6 +703,15 @@ exprTypmod(Node *expr)
701703
}
702704
}
703705
break;
706+
caseT_Expr:
707+
{
708+
int32coercedTypmod;
709+
710+
/* Be smart about length-coercion functions... */
711+
if (exprIsLengthCoercion(expr,&coercedTypmod))
712+
returncoercedTypmod;
713+
}
714+
break;
704715
caseT_RelabelType:
705716
return ((RelabelType*)expr)->resulttypmod;
706717
break;
@@ -710,6 +721,97 @@ exprTypmod(Node *expr)
710721
return-1;
711722
}
712723

724+
/*
725+
* exprIsLengthCoercion
726+
*Detect whether an expression tree is an application of a datatype's
727+
*typmod-coercion function. Optionally extract the result's typmod.
728+
*
729+
* If coercedTypmod is not NULL, the typmod is stored there if the expression
730+
* is a length-coercion function, else -1 is stored there.
731+
*
732+
* We assume that a two-argument function named for a datatype, whose
733+
* output and first argument types are that datatype, and whose second
734+
* input is an int32 constant, represents a forced length coercion.
735+
* XXX It'd be better if the parsetree retained some explicit indication
736+
* of the coercion, so we didn't need these heuristics.
737+
*/
738+
bool
739+
exprIsLengthCoercion(Node*expr,int32*coercedTypmod)
740+
{
741+
Func*func;
742+
Const*second_arg;
743+
HeapTupletup;
744+
Form_pg_procprocStruct;
745+
Form_pg_typetypeStruct;
746+
747+
if (coercedTypmod!=NULL)
748+
*coercedTypmod=-1;/* default result on failure */
749+
750+
/* Is it a function-call at all? */
751+
if (expr==NULL||
752+
!IsA(expr,Expr)||
753+
((Expr*)expr)->opType!=FUNC_EXPR)
754+
return false;
755+
func= (Func*) (((Expr*)expr)->oper);
756+
Assert(IsA(func,Func));
757+
758+
/*
759+
* If it's not a two-argument function with the second argument being
760+
* an int4 constant, it can't have been created from a length coercion.
761+
*/
762+
if (length(((Expr*)expr)->args)!=2)
763+
return false;
764+
second_arg= (Const*)lsecond(((Expr*)expr)->args);
765+
if (!IsA(second_arg,Const)||
766+
second_arg->consttype!=INT4OID||
767+
second_arg->constisnull)
768+
return false;
769+
770+
/*
771+
* Lookup the function in pg_proc
772+
*/
773+
tup=SearchSysCacheTuple(PROCOID,
774+
ObjectIdGetDatum(func->funcid),
775+
0,0,0);
776+
if (!HeapTupleIsValid(tup))
777+
elog(ERROR,"cache lookup for proc %u failed",func->funcid);
778+
procStruct= (Form_pg_proc)GETSTRUCT(tup);
779+
780+
/*
781+
* It must be a function with two arguments where the first is of
782+
* the same type as the return value and the second is an int4.
783+
* Also, just to be sure, check return type agrees with expr node.
784+
*/
785+
if (procStruct->pronargs!=2||
786+
procStruct->prorettype!=procStruct->proargtypes[0]||
787+
procStruct->proargtypes[1]!=INT4OID||
788+
procStruct->prorettype!= ((Expr*)expr)->typeOid)
789+
return false;
790+
791+
/*
792+
* Furthermore, the name of the function must be the same
793+
* as the argument/result type's name.
794+
*/
795+
tup=SearchSysCacheTuple(TYPEOID,
796+
ObjectIdGetDatum(procStruct->prorettype),
797+
0,0,0);
798+
if (!HeapTupleIsValid(tup))
799+
elog(ERROR,"cache lookup for type %u failed",
800+
procStruct->prorettype);
801+
typeStruct= (Form_pg_type)GETSTRUCT(tup);
802+
if (strncmp(NameStr(procStruct->proname),
803+
NameStr(typeStruct->typname),
804+
NAMEDATALEN)!=0)
805+
return false;
806+
807+
/*
808+
* OK, it is indeed a length-coercion function.
809+
*/
810+
if (coercedTypmod!=NULL)
811+
*coercedTypmod=DatumGetInt32(second_arg->constvalue);
812+
return true;
813+
}
814+
713815
/*
714816
* Produce an appropriate Const node from a constant value produced
715817
* by the parser and an explicit type name to cast to.

‎src/include/parser/parse_expr.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $Id: parse_expr.h,v 1.16 2000/01/2605:58:27 momjian Exp $
10+
* $Id: parse_expr.h,v 1.17 2000/02/2621:11:09 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -23,5 +23,6 @@
2323
externNode*transformExpr(ParseState*pstate,Node*expr,intprecedence);
2424
externOidexprType(Node*expr);
2525
externint32exprTypmod(Node*expr);
26+
externboolexprIsLengthCoercion(Node*expr,int32*coercedTypmod);
2627

2728
#endif/* PARSE_EXPR_H */

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