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From: Henson Choi <[email protected]>
To: Ashutosh Bapat <[email protected]>
To: Junwang Zhao <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: SQL/PGQ: All properties reference
Date: Fri, 3 Apr 2026 10:53:54 +0900
Message-ID: <CAAAe_zD3==epK=KufoBiLfogztpKbimxc498TUshTOQkkpgOjg@mail.gmail.com> (raw)
In-Reply-To: <CAExHW5tYCE9QyCvVraKUeesKW5RTR+mrzsg3u64qSps-RPJR5A@mail.gmail.com>
References: <CAExHW5tYCE9QyCvVraKUeesKW5RTR+mrzsg3u64qSps-RPJR5A@mail.gmail.com>

Hi Ashutosh,

I am starting a new thread to discuss all properties reference feature
> which was not committed with the main patch. [1]
>
> A <variable>.* is called all properties reference and it is allowed
> only in COLUMNs clause. Interpreting subclause 9.2 and 9.3 together,
> it expands to a list of graph property references <variable>.p1, ...
> <variable>.pn where p1, ..., pn are the properties of the labels which
> satisfy the label expression in the element pattern identified by
> <variable>. The graph property references are added to the COLUMNs
> clause in place of the all property reference, just like how <table>.*
> expands in SELECT's targetlist.
>
> In the current implementation, we delay resolving graph property
> references (<variable>.<property>) till the time query is generated
> (generate_query_for_graph_path()). If we delay the all properties
> reference till that time, we can not determine the data types and
> names of the columns in the COLUMNs list. So we need to do that when
> the COLUMNs clause is resolved. This means that the properties
> associated with the labels needs to be resolved earlier. Since the
> properties are not associated with labels directly but through the
> elements, we need to find at least one element for every label in the
> label expression. In brief, all the namespace resolution need to
> happen before we transform COLUMNs clause. The patch rearranges the
> code that way.
>

I tried applying v20260318 on top of master to review it, but ran
into merge conflicts in two files:

- parse_graphtable.c
- rewriteGraphTable.c

The conflicts come from this commit that was added after the main PGQ
commit (2f094e7ac69):

- a0dd0702e46 Fix cross variable references in graph pattern causing
  segfault

Would it be possible to rebase the patch on the current master so
I can review it cleanly?

Best Regards,
Henson

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