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Represent type-specific length coercion functions as pg_cast entries,

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eliminating the former hard-wired convention about their names.  Allow
pg_cast entries to represent both type coercion and length coercion in
a single step --- this is represented by a function that takes an
extra typmod argument, just like a length coercion function.  This
nicely merges the type and length coercion mechanisms into something
at least a little cleaner than we had before.  Make use of the single-
coercion-step behavior to fix integer-to-bit coercion so that coercing
to bit(n) yields the rightmost n bits of the integer instead of the
leftmost n bits.  This should fix recurrent complaints about the odd
behavior of this coercion.  Clean up the documentation of the bit string
functions, and try to put it where people might actually find it.
Also, get rid of the unreliable heuristics in ruleutils.c about whether
to display nested coercion steps; instead require parse_coerce.c to
label them properly in the first place.
This commit is contained in:
Tom Lane
2004-06-16 01:27:00 +00:00
parent 8e7349b738
commit d70a42e642
23 changed files with 794 additions and 471 deletions
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327
src/backend/parser/parse_coerce.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.118 2004/06/06 00:41:26 tgl Exp $
* $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.119 2004/06/16 01:26:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -33,8 +33,13 @@
static Node *coerce_type_typmod(Node *node,
Oid targetTypeId, int32 targetTypMod,
CoercionForm cformat, bool isExplicit);
Oid targetTypeId, int32 targetTypMod,
CoercionForm cformat, bool isExplicit,
bool hideInputCoercion);
static void hide_coercion_node(Node *node);
static Node *build_coercion_expression(Node *node, Oid funcId,
Oid targetTypeId, int32 targetTypMod,
CoercionForm cformat, bool isExplicit);
static Node *coerce_record_to_complex(ParseState *pstate, Node *node,
Oid targetTypeId,
CoercionContext ccontext,
@ -67,22 +72,27 @@ coerce_to_target_type(ParseState *pstate, Node *expr, Oid exprtype,
CoercionContext ccontext,
CoercionForm cformat)
{
if (can_coerce_type(1, &exprtype, &targettype, ccontext))
expr = coerce_type(pstate, expr, exprtype, targettype,
ccontext, cformat);
else
expr = NULL;
Node *result;
if (!can_coerce_type(1, &exprtype, &targettype, ccontext))
return NULL;
result = coerce_type(pstate, expr, exprtype,
targettype, targettypmod,
ccontext, cformat);
/*
* If the target is a fixed-length type, it may need a length coercion
* as well as a type coercion.
* as well as a type coercion. If we find ourselves adding both,
* force the inner coercion node to implicit display form.
*/
if (expr != NULL)
expr = coerce_type_typmod(expr, targettype, targettypmod,
cformat,
(cformat != COERCE_IMPLICIT_CAST));
result = coerce_type_typmod(result,
targettype, targettypmod,
cformat,
(cformat != COERCE_IMPLICIT_CAST),
(result != expr && !IsA(result, Const)));
return expr;
return result;
}
@ -93,10 +103,13 @@ coerce_to_target_type(ParseState *pstate, Node *expr, Oid exprtype,
* The caller should already have determined that the coercion is possible;
* see can_coerce_type.
*
* No coercion to a typmod (length) is performed here. The caller must
* call coerce_type_typmod as well, if a typmod constraint is wanted.
* Normally, no coercion to a typmod (length) is performed here. The caller
* must call coerce_type_typmod as well, if a typmod constraint is wanted.
* (But if the target type is a domain, it may internally contain a
* typmod constraint, which will be applied inside coerce_to_domain.)
* In some cases pg_cast specifies a type coercion function that also
* applies length conversion, and in those cases only, the result will
* already be properly coerced to the specified typmod.
*
* pstate is only used in the case that we are able to resolve the type of
* a previously UNKNOWN Param. It is okay to pass pstate = NULL if the
@ -104,7 +117,7 @@ coerce_to_target_type(ParseState *pstate, Node *expr, Oid exprtype,
*/
Node *
coerce_type(ParseState *pstate, Node *node,
Oid inputTypeId, Oid targetTypeId,
Oid inputTypeId, Oid targetTypeId, int32 targetTypeMod,
CoercionContext ccontext, CoercionForm cformat)
{
Node *result;
@ -178,7 +191,7 @@ coerce_type(ParseState *pstate, Node *node,
/* If target is a domain, apply constraints. */
if (targetTyptype == 'd')
result = coerce_to_domain(result, InvalidOid, targetTypeId,
cformat);
cformat, false);
ReleaseSysCache(targetType);
@ -240,13 +253,14 @@ coerce_type(ParseState *pstate, Node *node,
* Generate an expression tree representing run-time
* application of the conversion function. If we are dealing
* with a domain target type, the conversion function will
* yield the base type.
* yield the base type (and we assume targetTypeMod must be -1).
*/
Oid baseTypeId = getBaseType(targetTypeId);
result = (Node *) makeFuncExpr(funcId, baseTypeId,
list_make1(node),
cformat);
result = build_coercion_expression(node, funcId,
baseTypeId, targetTypeMod,
cformat,
(cformat != COERCE_IMPLICIT_CAST));
/*
* If domain, coerce to the domain type and relabel with
@ -254,7 +268,7 @@ coerce_type(ParseState *pstate, Node *node,
*/
if (targetTypeId != baseTypeId)
result = coerce_to_domain(result, baseTypeId, targetTypeId,
cformat);
cformat, true);
}
else
{
@ -269,7 +283,7 @@ coerce_type(ParseState *pstate, Node *node,
* then we won't need a RelabelType node.
*/
result = coerce_to_domain(node, InvalidOid, targetTypeId,
cformat);
cformat, false);
if (result == node)
{
/*
@ -409,11 +423,13 @@ can_coerce_type(int nargs, Oid *input_typeids, Oid *target_typeids,
* has not bothered to look this up)
* 'typeId': target type to coerce to
* 'cformat': coercion format
* 'hideInputCoercion': if true, hide the input coercion under this one.
*
* If the target type isn't a domain, the given 'arg' is returned as-is.
*/
Node *
coerce_to_domain(Node *arg, Oid baseTypeId, Oid typeId, CoercionForm cformat)
coerce_to_domain(Node *arg, Oid baseTypeId, Oid typeId,
CoercionForm cformat, bool hideInputCoercion)
{
CoerceToDomain *result;
int32 typmod;
@ -426,6 +442,10 @@ coerce_to_domain(Node *arg, Oid baseTypeId, Oid typeId, CoercionForm cformat)
if (baseTypeId == typeId)
return arg;
/* Suppress display of nested coercion steps */
if (hideInputCoercion)
hide_coercion_node(arg);
/*
* If the domain applies a typmod to its base type, build the
* appropriate coercion step. Mark it implicit for display purposes,
@ -444,7 +464,8 @@ coerce_to_domain(Node *arg, Oid baseTypeId, Oid typeId, CoercionForm cformat)
if (typmod >= 0)
arg = coerce_type_typmod(arg, baseTypeId, typmod,
COERCE_IMPLICIT_CAST,
(cformat != COERCE_IMPLICIT_CAST));
(cformat != COERCE_IMPLICIT_CAST),
false);
/*
* Now build the domain coercion node. This represents run-time
@ -473,57 +494,142 @@ coerce_to_domain(Node *arg, Oid baseTypeId, Oid typeId, CoercionForm cformat)
* The caller must have already ensured that the value is of the correct
* type, typically by applying coerce_type.
*
* cformat determines the display properties of the generated node (if any),
* while isExplicit may affect semantics. If hideInputCoercion is true
* *and* we generate a node, the input node is forced to IMPLICIT display
* form, so that only the typmod coercion node will be visible when
* displaying the expression.
*
* NOTE: this does not need to work on domain types, because any typmod
* coercion for a domain is considered to be part of the type coercion
* needed to produce the domain value in the first place. So, no getBaseType.
*/
static Node *
coerce_type_typmod(Node *node, Oid targetTypeId, int32 targetTypMod,
CoercionForm cformat, bool isExplicit)
CoercionForm cformat, bool isExplicit,
bool hideInputCoercion)
{
Oid funcId;
int nargs;
/*
* A negative typmod is assumed to mean that no coercion is wanted.
* Also, skip coercion if already done.
*/
if (targetTypMod < 0 || targetTypMod == exprTypmod(node))
return node;
funcId = find_typmod_coercion_function(targetTypeId, &nargs);
funcId = find_typmod_coercion_function(targetTypeId);
if (OidIsValid(funcId))
{
List *args;
Const *cons;
/* Suppress display of nested coercion steps */
if (hideInputCoercion)
hide_coercion_node(node);
/* Pass given value, plus target typmod as an int4 constant */
node = build_coercion_expression(node, funcId,
targetTypeId, targetTypMod,
cformat, isExplicit);
}
return node;
}
/*
* Mark a coercion node as IMPLICIT so it will never be displayed by
* ruleutils.c. We use this when we generate a nest of coercion nodes
* to implement what is logically one conversion; the inner nodes are
* forced to IMPLICIT_CAST format. This does not change their semantics,
* only display behavior.
*
* It is caller error to call this on something that doesn't have a
* CoercionForm field.
*/
static void
hide_coercion_node(Node *node)
{
if (IsA(node, FuncExpr))
((FuncExpr *) node)->funcformat = COERCE_IMPLICIT_CAST;
else if (IsA(node, RelabelType))
((RelabelType *) node)->relabelformat = COERCE_IMPLICIT_CAST;
else if (IsA(node, RowExpr))
((RowExpr *) node)->row_format = COERCE_IMPLICIT_CAST;
else if (IsA(node, CoerceToDomain))
((CoerceToDomain *) node)->coercionformat = COERCE_IMPLICIT_CAST;
else
elog(ERROR, "unsupported node type: %d", (int) nodeTag(node));
}
/*
* build_coercion_expression()
* Construct a function-call expression for applying a pg_cast entry.
*
* This is used for both type-coercion and length-coercion functions,
* since there is no difference in terms of the calling convention.
*/
static Node *
build_coercion_expression(Node *node, Oid funcId,
Oid targetTypeId, int32 targetTypMod,
CoercionForm cformat, bool isExplicit)
{
HeapTuple tp;
Form_pg_proc procstruct;
int nargs;
List *args;
Const *cons;
tp = SearchSysCache(PROCOID,
ObjectIdGetDatum(funcId),
0, 0, 0);
if (!HeapTupleIsValid(tp))
elog(ERROR, "cache lookup failed for function %u", funcId);
procstruct = (Form_pg_proc) GETSTRUCT(tp);
/*
* Asserts essentially check that function is a legal coercion function.
* We can't make the seemingly obvious tests on prorettype and
* proargtypes[0], because of various binary-compatibility cases.
*/
/* Assert(targetTypeId == procstruct->prorettype); */
Assert(!procstruct->proretset);
Assert(!procstruct->proisagg);
nargs = procstruct->pronargs;
Assert(nargs >= 1 && nargs <= 3);
/* Assert(procstruct->proargtypes[0] == exprType(node)); */
Assert(nargs < 2 || procstruct->proargtypes[1] == INT4OID);
Assert(nargs < 3 || procstruct->proargtypes[2] == BOOLOID);
ReleaseSysCache(tp);
args = list_make1(node);
if (nargs >= 2)
{
/* Pass target typmod as an int4 constant */
cons = makeConst(INT4OID,
sizeof(int32),
Int32GetDatum(targetTypMod),
false,
true);
args = list_make2(node, cons);
if (nargs == 3)
{
/* Pass it a boolean isExplicit parameter, too */
cons = makeConst(BOOLOID,
sizeof(bool),
BoolGetDatum(isExplicit),
false,
true);
args = lappend(args, cons);
}
node = (Node *) makeFuncExpr(funcId, targetTypeId, args, cformat);
args = lappend(args, cons);
}
return node;
if (nargs == 3)
{
/* Pass it a boolean isExplicit parameter, too */
cons = makeConst(BOOLOID,
sizeof(bool),
BoolGetDatum(isExplicit),
false,
true);
args = lappend(args, cons);
}
return (Node *) makeFuncExpr(funcId, targetTypeId, args, cformat);
}
/*
* coerce_record_to_complex
* Coerce a RECORD to a specific composite type.
@ -803,7 +909,7 @@ coerce_to_common_type(ParseState *pstate, Node *node,
if (inputTypeId == targetTypeId)
return node; /* no work */
if (can_coerce_type(1, &inputTypeId, &targetTypeId, COERCION_IMPLICIT))
node = coerce_type(pstate, node, inputTypeId, targetTypeId,
node = coerce_type(pstate, node, inputTypeId, targetTypeId, -1,
COERCION_IMPLICIT, COERCE_IMPLICIT_CAST);
else
ereport(ERROR,
@ -1528,8 +1634,8 @@ find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
{
/*
* If there's no pg_cast entry, perhaps we are dealing with a pair
* of array types. If so, and if the element types have a
* suitable cast, use array_type_coerce().
* of array types. If so, and if the element types have a suitable
* cast, use array_type_coerce() or array_type_length_coerce().
*/
Oid targetElemType;
Oid sourceElemType;
@ -1541,7 +1647,23 @@ find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
if (find_coercion_pathway(targetElemType, sourceElemType,
ccontext, &elemfuncid))
{
*funcid = F_ARRAY_TYPE_COERCE;
if (!OidIsValid(elemfuncid))
{
/* binary-compatible element type conversion */
*funcid = F_ARRAY_TYPE_COERCE;
}
else
{
/* does the function take a typmod arg? */
Oid argtypes[FUNC_MAX_ARGS];
int nargs;
(void) get_func_signature(elemfuncid, argtypes, &nargs);
if (nargs > 1)
*funcid = F_ARRAY_TYPE_LENGTH_COERCE;
else
*funcid = F_ARRAY_TYPE_COERCE;
}
result = true;
}
}
@ -1554,14 +1676,8 @@ find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
/*
* find_typmod_coercion_function -- does the given type need length coercion?
*
* If the target type possesses a function named for the type
* and having parameter signature (targettype, int4), we assume that
* the type requires coercion to its own length and that the said
* function should be invoked to do that.
*
* Alternatively, the length-coercing function may have the signature
* (targettype, int4, bool). On success, *nargs is set to report which
* signature we found.
* If the target type possesses a pg_cast function from itself to itself,
* it must need length coercion.
*
* "bpchar" (ie, char(N)) and "numeric" are examples of such types.
*
@ -1569,23 +1685,15 @@ find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
* function associated directly with the array type, but instead look for
* one associated with the element type. If one exists, we report
* array_length_coerce() as the coercion function to use.
*
* This mechanism may seem pretty grotty and in need of replacement by
* something in pg_cast, but since typmod is only interesting for datatypes
* that have special handling in the grammar, there's not really much
* percentage in making it any easier to apply such coercions ...
*/
Oid
find_typmod_coercion_function(Oid typeId, int *nargs)
find_typmod_coercion_function(Oid typeId)
{
Oid funcid = InvalidOid;
bool isArray = false;
Type targetType;
Form_pg_type typeForm;
char *typname;
Oid typnamespace;
Oid oid_array[FUNC_MAX_ARGS];
HeapTuple ftup;
HeapTuple tuple;
targetType = typeidType(typeId);
typeForm = (Form_pg_type) GETSTRUCT(targetType);
@ -1597,79 +1705,30 @@ find_typmod_coercion_function(Oid typeId, int *nargs)
{
/* Yes, switch our attention to the element type */
typeId = typeForm->typelem;
ReleaseSysCache(targetType);
targetType = typeidType(typeId);
typeForm = (Form_pg_type) GETSTRUCT(targetType);
isArray = true;
}
/* Function name is same as type internal name, and in same namespace */
typname = NameStr(typeForm->typname);
typnamespace = typeForm->typnamespace;
/* First look for parameters (type, int4) */
MemSet(oid_array, 0, FUNC_MAX_ARGS * sizeof(Oid));
oid_array[0] = typeId;
oid_array[1] = INT4OID;
*nargs = 2;
ftup = SearchSysCache(PROCNAMENSP,
CStringGetDatum(typname),
Int16GetDatum(2),
PointerGetDatum(oid_array),
ObjectIdGetDatum(typnamespace));
if (HeapTupleIsValid(ftup))
{
Form_pg_proc pform = (Form_pg_proc) GETSTRUCT(ftup);
/* Make sure the function's result type is as expected */
if (pform->prorettype == typeId && !pform->proretset &&
!pform->proisagg)
{
/* Okay to use it */
funcid = HeapTupleGetOid(ftup);
}
ReleaseSysCache(ftup);
}
if (!OidIsValid(funcid))
{
/* Didn't find a function, so now try (type, int4, bool) */
oid_array[2] = BOOLOID;
*nargs = 3;
ftup = SearchSysCache(PROCNAMENSP,
CStringGetDatum(typname),
Int16GetDatum(3),
PointerGetDatum(oid_array),
ObjectIdGetDatum(typnamespace));
if (HeapTupleIsValid(ftup))
{
Form_pg_proc pform = (Form_pg_proc) GETSTRUCT(ftup);
/* Make sure the function's result type is as expected */
if (pform->prorettype == typeId && !pform->proretset &&
!pform->proisagg)
{
/* Okay to use it */
funcid = HeapTupleGetOid(ftup);
}
ReleaseSysCache(ftup);
}
}
ReleaseSysCache(targetType);
/* Look in pg_cast */
tuple = SearchSysCache(CASTSOURCETARGET,
ObjectIdGetDatum(typeId),
ObjectIdGetDatum(typeId),
0, 0);
if (HeapTupleIsValid(tuple))
{
Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);
funcid = castForm->castfunc;
ReleaseSysCache(tuple);
}
/*
* Now, if we did find a coercion function for an array element type,
* report array_length_coerce() as the function to use. We know it
* takes three arguments always.
* report array_length_coerce() as the function to use.
*/
if (isArray && OidIsValid(funcid))
{
funcid = F_ARRAY_LENGTH_COERCE;
*nargs = 3;
}
return funcid;
}