Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options

Overall LGTM. Just a few small comments:

> On Sep 12, 2025, at 17:53, Tatsuo Ishii <ishii(at)postgresql(dot)org> wrote:
>
>
> Comments/suggestions are welcome.
> --
> Tatsuo Ishii
> SRA OSS K.K.
> English: http://www.sraoss.co.jp/index_en/
> Japanese:http://www.sraoss.co.jp
>

1 - 0001
```
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
bool agg_star = (fn ? fn->agg_star : false);
bool agg_distinct = (fn ? fn->agg_distinct : false);
bool func_variadic = (fn ? fn->func_variadic : false);
+ int ignore_nulls = (fn ? fn->ignore_nulls : 0);
```

Should we use the constant NO_NULLTREATMENT here for 0?

2 - 0001
```
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
* Collation information is irrelevant for the query jumbling, as is the
* internal state information of the node like "winstar" and "winagg".
*/
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
typedef struct WindowFunc
{
Expr xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
bool winstar pg_node_attr(query_jumble_ignore);
/* is function a simple aggregate? */
bool winagg pg_node_attr(query_jumble_ignore);
+ /* ignore nulls. One of the Null Treatment options */
+ int ignore_nulls;
```

Maybe we can use “uint8” type for “ignore_nulls”. Because the previous two are both of type “bool”, an uint8 will just fit to the padding bytes, so that new field won’t add extra memory to the structure.

3 - 0004
```
winobj->markpos = -1;
winobj->seekpos = -1;
+
+ /* reset null map */
+ if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+ memset(perfuncstate->winobj->notnull_info, 0,
+ NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
}
```
Where in “if” and “memset()”, we can just use “winobj”.

4 - 0004
```
+ if (!HeapTupleIsValid(proctup))
+ elog(ERROR, "cache lookup failed for function %u", funcid);
+ procform = (Form_pg_proc) GETSTRUCT(proctup);
+ elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+ NameStr(procform->proname));
```

“Procform” is assigned but not used.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/