Re: Row pattern recognition

> On Nov 18, 2025, at 19:19, Vik Fearing <vik(at)postgresfriends(dot)org> wrote:
>
>
> Because of position. Without making DEFINE a reserved keyword, how do you know that it isn't another variable in the PATTERN clause?
>

Ah, thanks for the clarification. Now I got it.

I’m continue to review 0002.

5 - 0002 - parse_clause.c
```
+ ereport(ERROR,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("FRAME must start at current row when row patttern recognition is used")));
```

Nit typo: patttern -> pattern

6 - 0002 - parse_clause.c
```
+ /* DEFINE variable name initials */
+ static char *defineVariableInitials = "abcdefghijklmnopqrstuvwxyz”;
```

This string can also be const, so “static const char *”

7 - 0002 - parse_clause.c
```
+ /*
+ * Create list of row pattern DEFINE variable name's initial. We assign
+ * [a-z] to them (up to 26 variable names are allowed).
+ */
+ restargets = NIL;
+ i = 0;
+ initialLen = strlen(defineVariableInitials);
+
+ foreach(lc, windef->rpCommonSyntax->rpDefs)
+ {
+ char initial[2];
+
+ restarget = (ResTarget *) lfirst(lc);
+ name = restarget->name;
```

Looks like “name” is not used inside “foreach”.

8 - 0002 - parse_clause.c
```
+ /*
+ * Create list of row pattern DEFINE variable name's initial. We assign
+ * [a-z] to them (up to 26 variable names are allowed).
+ */
+ restargets = NIL;
+ i = 0;
+ initialLen = strlen(defineVariableInitials);
+
+ foreach(lc, windef->rpCommonSyntax->rpDefs)
+ {
+ char initial[2];
```

I guess this “foreach” for build initial list can be combined into the previous foreach loop of checking duplication. If an def has no dup, then assign an initial to it.

9 - 0002 - parse_clause.c
```
+static void
+transformPatternClause(ParseState *pstate, WindowClause *wc,
+ WindowDef *windef)
+{
+ ListCell *lc;
+
+ /*
+ * Row Pattern Common Syntax clause exists?
+ */
+ if (windef->rpCommonSyntax == NULL)
+ return;
```

Checking (windef->rpCommonSyntax == NULL) seems a duplicate, because transformPatternClause() is only called by transformRPR(), and transformRPR() has done the check.

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