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Code review for protransform patches.

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Fix loss of previous expression-simplification work when a transform
function fires: we must not simply revert to untransformed input tree.
Instead build a dummy FuncExpr node to pass to the transform function.
This has the additional advantage of providing a simpler, more uniform
API for transform functions.

Move documentation to a somewhat less buried spot, relocate some
poorly-placed code, be more wary of null constants and invalid typmod
values, add an opr_sanity check on protransform function signatures,
and some other minor cosmetic adjustments.

Note: although this patch touches pg_proc.h, no need for catversion
bump, because the changes are cosmetic and don't actually change the
intended catalog contents.
This commit is contained in:
Tom Lane
2012-03-23 17:29:57 -04:00
parent e08b4101e1
commit 0339047bc9
15 changed files with 205 additions and 172 deletions
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26
src/backend/utils/adt/varchar.c
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@@ -19,7 +19,6 @@
#include "access/tuptoaster.h"
#include "libpq/pqformat.h"
#include "nodes/nodeFuncs.h"
#include "parser/parse_clause.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "mb/pg_wchar.h"
@@ -551,31 +550,32 @@ varcharsend(PG_FUNCTION_ARGS)
/*
* Flatten calls to our length coercion function that leave the new maximum
* length >= the previous maximum length. We ignore the isExplicit argument,
* which only affects truncation.
* varchar_transform()
* Flatten calls to varchar's length coercion function that set the new maximum
* length >= the previous maximum length. We can ignore the isExplicit
* argument, since that only affects truncation cases.
*/
Datum
varchar_transform(PG_FUNCTION_ARGS)
{
FuncExpr *expr = (FuncExpr *) PG_GETARG_POINTER(0);
Node *typmod;
Node *ret = NULL;
Node *typmod;
if (!IsA(expr, FuncExpr))
PG_RETURN_POINTER(ret);
Assert(IsA(expr, FuncExpr));
Assert(list_length(expr->args) >= 2);
Assert(list_length(expr->args) == 3);
typmod = lsecond(expr->args);
typmod = (Node *) lsecond(expr->args);
if (IsA(typmod, Const))
if (IsA(typmod, Const) && !((Const *) typmod)->constisnull)
{
Node *source = linitial(expr->args);
Node *source = (Node *) linitial(expr->args);
int32 old_typmod = exprTypmod(source);
int32 new_typmod = DatumGetInt32(((Const *) typmod)->constvalue);
int32 old_max = exprTypmod(source) - VARHDRSZ;
int32 old_max = old_typmod - VARHDRSZ;
int32 new_max = new_typmod - VARHDRSZ;
if (new_max < 0 || (old_max >= 0 && old_max <= new_max))
if (new_typmod < 0 || (old_typmod >= 0 && old_max <= new_max))
ret = relabel_to_typmod(source, new_typmod);
}