| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Erik Rijkers <er(at)xs4all(dot)nl>, Kevin Grittner <kgrittn(at)mail(dot)com>, pgsql-hackers(at)postgresql(dot)org, Andres Freund <andres(at)2ndquadrant(dot)com> |
| Subject: | Re: foreign key locks |
| Date: | 2013-01-18 20:37:47 |
| Message-ID: | 28623.1358541467@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> The reason is that there is an (unknown to me) rule that there must be
> some data not associated with a buffer:
> /*
> * NOTE: We disallow len == 0 because it provides a useful bit of extra
> * error checking in ReadRecord. This means that all callers of
> * XLogInsert must supply at least some not-in-a-buffer data. [...]
> */
> This seems pretty strange to me. And having the rule be spelled out
> only in a comment within XLogInsert and not at its top, and not nearby
> the XLogRecData struct definition either, seems pretty strange to me.
> I wonder how come every PG hacker except me knows this.
I doubt it ever came up before. What use is logging only the content of
a buffer page? Surely you'd need to know, for example, which relation
and page number it is from.
regards, tom lane
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