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Fix outdated comment that talked about seek position of WAL file.

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Since commit c24dcd0cfd, we have been using pg_pread() to read the WAL
file, which doesn't change the seek position (unless we fall back to
the implementation in src/port/pread.c). Update comment accordingly.

Backpatch-through: 12, where we started to use pg_pread()
This commit is contained in:
Heikki Linnakangas 2021-06-16 12:34:32 +03:00
parent d906d106f8
commit e89a8e30e0
1 changed files with 3 additions and 5 deletions
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8
src/backend/access/transam/xlog.c
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@ -801,11 +801,9 @@ static XLogSegNo openLogSegNo = 0;
/* /*
* These variables are used similarly to the ones above, but for reading * These variables are used similarly to the ones above, but for reading
* the XLOG. Note, however, that readOff generally represents the offset * the XLOG. readOff is the offset of the page just read, readLen
* of the page just read, not the seek position of the FD itself, which * indicates how much of it has been read into readBuf, and readSource
* will be just past that page. readLen indicates how much of the current * indicates where we got the currently open file from.
* page has been read into readBuf, and readSource indicates where we got
* the currently open file from.
* Note: we could use Reserve/ReleaseExternalFD to track consumption of * Note: we could use Reserve/ReleaseExternalFD to track consumption of
* this FD too; but it doesn't currently seem worthwhile, since the XLOG is * this FD too; but it doesn't currently seem worthwhile, since the XLOG is
* not read by general-purpose sessions. * not read by general-purpose sessions.