Incorrect errno used in OpenWalSummaryFile()

[Michael Paquier]

Hi all,

While looking at walsummary.c for a different thread, I have bumped
into this code:
OpenWalSummaryFile(WalSummaryFile *ws, bool missing_ok)
[...]
    file = PathNameOpenFile(path, O_RDONLY);
    if (file < 0 && (errno != EEXIST || !missing_ok))
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m", path)));

And it seems to me that this EEXIST should be an ENOENT?  The top of
the function also documents that we want to handle an error when a
summary file does not exist.  The comment makes sense to me, not the
code.

It's also worth noting that this function has two callers, both use
missing_ok = false, meaning that the errno check does not really
matter today.  If someone plays with this code on HEAD or the
back-branches and decides to introduce a missing_ok=true call, it
could matter, so I'd rather not change this function signature.

This issue has been mentioned here as well, I've just bumped into it
independently a few hours ago:
https://www.postgresql.org/message-id/tencent_1ca40fcc21c1c770712bc...@qq.com

Regards,
--
Michael

diff --git a/src/backend/backup/walsummary.c b/src/backend/backup/walsummary.c
index 4ee510092f99..4cd1824fbc6b 100644
--- a/src/backend/backup/walsummary.c
+++ b/src/backend/backup/walsummary.c
@@ -214,7 +214,7 @@ OpenWalSummaryFile(WalSummaryFile *ws, bool missing_ok)
                         LSN_FORMAT_ARGS(ws->end_lsn));
 
        file = PathNameOpenFile(path, O_RDONLY);
-       if (file < 0 && (errno != EEXIST || !missing_ok))
+       if (file < 0 && (errno != ENOENT || !missing_ok))
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not open file \"%s\": %m", 
path)));

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