Re: Row pattern recognition

Hi Henson,

> The standard does not allow to use range variables, declared in the
>> FROM clause, in the DEFINE clause (19075-5 6.5). Attached patch raises
>> an error in this case.
>>
>
> Agreed. §6.5 is explicit about mutual exclusivity of the two sets of
> range variables. Your patch is correct for this case.
>
> Also, currently we do not support pattern variable range vars in the
>> DEFINE caluse (e.g. UP.price). If used, we see a confusing error
>> message:
>>
>> ERROR: missing FROM-clause entry for table "UP"
>> LINE 13: UP AS UP.price > PREV(price),
>> ^
>>
>
> Pattern variable qualified names like `UP.price` are actually valid
> standard syntax (§4.16 uses them in examples), so "is not allowed"
> is misleading ― "is not supported" would be more accurate.

Fair enough.

> To distinguish the two cases, we could expose `patternVarNames` via
> ParseState (it is already collected by `validateRPRPatternVarCount`
> before DEFINE expressions are transformed) and check in
> `transformColumnRef` whether the qualifier is a pattern variable:

Oh, I didn't realize it.

> - pattern variable qualifier → "not supported"
> - anything else → "not allowed"
>
> Would it be okay if I revise the patch along those lines?

Sure. Thanks.
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
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