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Re: Opclass parameters of indexes lost after REINDEX CONCURRENTLY - Mailing list pgsql-hackers

From Zhihong Yu
Subject Re: Opclass parameters of indexes lost after REINDEX CONCURRENTLY
Date
Msg-id CALNJ-vSmR7B1YGwDqBbSNM=bON8W+sPWC0AmXYPTwFgT7cXFbA@mail.gmail.com
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In response to Opclass parameters of indexes lost after REINDEX CONCURRENTLY  (Michael Paquier <michael@paquier.xyz>)
Responses Re: Opclass parameters of indexes lost after REINDEX CONCURRENTLY
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On Sat, Oct 30, 2021 at 1:28 AM Michael Paquier <michael@paquier.xyz> wrote:
Hi all,

While reviewing the code for opclass parameters with indexes, I have
noticed that opclass parameters are lost after a concurrent reindex.
As we use a IndexInfo to hold the information of the new index when
creating a copy of the old one, it is just a matter of making sure
that ii_OpclassOptions is filled appropriately, but that was missed by
911e702.

Attached is a patch to fix the issue.  After a concurrent reindex, we
would not finish with a corrupted index, just with one rebuilt with
default opclass parameter values.

Any objections or comments?
--
Michael
Hi,

+       newInfo->ii_OpclassOptions = palloc0(sizeof(Datum) *
+                                            newInfo->ii_NumIndexAttrs);

It seems we may not need to allocate these many entries (as shown by the concur_appclass_ind_2 example in the test). 
In the previous loop (starting line 1359), we can increment a counter which would finally tell us how many oldInfo->ii_OpclassOptions[i] is not NULL.

Then that many entries can be allocated in the above code.

Cheers

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