Streaming Replication and Hash Indices

Started by Seb Melover 10 years ago2 messagesdocs
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#1Seb Mel
webmaster@mailz.de

Hi list,

today i got bitten by the issue that streaming replication does not replicate "hash" indices as those changes are not written to WAL. That fact is documented here:
http://www.postgresql.org/docs/current/static/indexes-types.html

But i could not find that information anywhere else like:
https://wiki.postgresql.org/wiki/Streaming_Replication#Restrictions
or
http://www.postgresql.org/docs/current/static/warm-standby.html

I suppose it would be very helpful to add it there, as the usual policy for "corrupt slave data" is to recreate the slave from a base_backup which would make you into thinking that the issue was fixed.
That is wrong though, as it will reappear after some time when the data in the table and the index diverge :)!

Regards,
Seb

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#2Bruce Momjian
bruce@momjian.us
In reply to: Seb Mel (#1)
Re: Streaming Replication and Hash Indices

On Mon, Jan 18, 2016 at 01:15:28PM +0100, Seb Mel wrote:

Hi list,

today i got bitten by the issue that streaming replication does not replicate "hash" indices as those changes are not written to WAL. That fact is documented here:
http://www.postgresql.org/docs/current/static/indexes-types.html

But i could not find that information anywhere else like:
https://wiki.postgresql.org/wiki/Streaming_Replication#Restrictions
or
http://www.postgresql.org/docs/current/static/warm-standby.html

I suppose it would be very helpful to add it there, as the usual policy for "corrupt slave data" is to recreate the slave from a base_backup which would make you into thinking that the issue was fixed.
That is wrong though, as it will reappear after some time when the data in the table and the index diverge :)!

We issue a warning on hash index creation in 9.5:

Issue a warning during the creation of <link
linkend="indexes-types">hash</> indexes because they are not
crash-safe (Bruce Momjian)

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Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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