Fix over-optimistic caching in fetch_array_arg_replace_nulls().

When I rewrote this in commit 56a79a869bedc4bf6c35853642694cc0b0594dd2,
I forgot that it's possible for the input array type to change from one
call to the next (this can happen when applying the function to
pg_statistic columns, for instance).  Fix that.

diff --git a/src/backend/utils/adt/array_userfuncs.c b/src/backend/utils/adt/array_userfuncs.c
index 5781b952f97b74c2df9918015f9673dc08dfa10c..667933352257e05b7726a7bd2cdf402827863b8c 100644 (file)
--- a/src/backend/utils/adt/array_userfuncs.c
+++ b/src/backend/utils/adt/array_userfuncs.c
@@ -28,14 +28,19 @@ static ArrayType *
 fetch_array_arg_replace_nulls(FunctionCallInfo fcinfo, int argno)
 {
        ArrayType  *v;
+       Oid                     element_type;
        ArrayMetaState *my_extra;
 
-       my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
-       if (my_extra == NULL)
+       /* First collect the array value */
+       if (!PG_ARGISNULL(argno))
+       {
+               v = PG_GETARG_ARRAYTYPE_P(argno);
+               element_type = ARR_ELEMTYPE(v);
+       }
+       else
        {
-               /* First time through, so look up the array type and element type */
+               /* We have to look up the array type and element type */
                Oid                     arr_typeid = get_fn_expr_argtype(fcinfo->flinfo, argno);
-               Oid                     element_type;
 
                if (!OidIsValid(arr_typeid))
                        ereport(ERROR,
@@ -47,26 +52,29 @@ fetch_array_arg_replace_nulls(FunctionCallInfo fcinfo, int argno)
                                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                                         errmsg("input data type is not an array")));
 
+               v = construct_empty_array(element_type);
+       }
+
+       /* Now cache required info, which might change from call to call */
+       my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
+       if (my_extra == NULL)
+       {
                my_extra = (ArrayMetaState *)
                        MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                                                           sizeof(ArrayMetaState));
-               my_extra->element_type = element_type;
+               my_extra->element_type = InvalidOid;
+               fcinfo->flinfo->fn_extra = my_extra;
+       }
 
-               /* Cache info about element type */
+       if (my_extra->element_type != element_type)
+       {
                get_typlenbyvalalign(element_type,
                                                         &my_extra->typlen,
                                                         &my_extra->typbyval,
                                                         &my_extra->typalign);
-
-               fcinfo->flinfo->fn_extra = my_extra;
+               my_extra->element_type = element_type;
        }
 
-       /* Now we can collect the array value */
-       if (PG_ARGISNULL(argno))
-               v = construct_empty_array(my_extra->element_type);
-       else
-               v = PG_GETARG_ARRAYTYPE_P(argno);
-
        return v;
 }