pg_xlog

[Reynard Hilman]

Hi,

Is there a way to translate information in pg_xlog files to a more
readable format?
Basically we have someone accidentally emptied a text column containing
quite a large amount of text, and unfortunately have no backups. I know
the pg_xlog is for WAL, and probably is not the proper way to restore a
lost data. but I find some of the text in one of the files in pg_xlog
directory. I can get the text part but there are also non text
characters. So just wondering if there is a way to interpret the non
text characters.

thanks,
- reynard


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[Bruce Momjian]

Reynard Hilman wrote:

Hi,

Is there a way to translate information in pg_xlog files to a more
readable format?
Basically we have someone accidentally emptied a text column containing
quite a large amount of text, and unfortunately have no backups. I know
the pg_xlog is for WAL, and probably is not the proper way to restore a
lost data. but I find some of the text in one of the files in pg_xlog
directory. I can get the text part but there are also non text
characters. So just wondering if there is a way to interpret the non
text characters.

No way to dump them. If you haven't vacuumed the data is still there
but just not visible because the transaction id that delete them is
marked as commited. If you can undo that or hack the code so delete
rows are visible you would see them. Such skills are quite complex,
however.

--
Bruce Momjian | http://candle.pha.pa.us
pg***@candle.ph a.pa.us | [phone]
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073

---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match

[Bruce Momjian]

Reynard Hilman wrote:

Hi,

Is there a way to translate information in pg_xlog files to a more
readable format?
Basically we have someone accidentally emptied a text column containing
quite a large amount of text, and unfortunately have no backups. I know
the pg_xlog is for WAL, and probably is not the proper way to restore a
lost data. but I find some of the text in one of the files in pg_xlog
directory. I can get the text part but there are also non text
characters. So just wondering if there is a way to interpret the non
text characters.

No way to dump them. If you haven't vacuumed the data is still there
but just not visible because the transaction id that delete them is
marked as commited. If you can undo that or hack the code so delete
rows are visible you would see them. Such skills are quite complex,
however.

--
Bruce Momjian | http://candle.pha.pa.us
pg***@candle.ph a.pa.us | [phone]
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073

---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match

[Tom Lane]

Reynard Hilman <re*******@ligh tsky.com> writes:

Is there a way to translate information in pg_xlog files to a more
readable format?
Basically we have someone accidentally emptied a text column containing
quite a large amount of text, and unfortunately have no backups.

No, and I don't think it would help you anyway. pg_xlog is only
intended as short-term backup; it's unlikely to contain data that is more
than a few minutes old.

regards, tom lane

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[Tom Lane]

Reynard Hilman <re*******@ligh tsky.com> writes:

Is there a way to translate information in pg_xlog files to a more
readable format?
Basically we have someone accidentally emptied a text column containing
quite a large amount of text, and unfortunately have no backups.

No, and I don't think it would help you anyway. pg_xlog is only
intended as short-term backup; it's unlikely to contain data that is more
than a few minutes old.

regards, tom lane

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