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List:       postgresql-general
Subject:    Re: GIN index
From:       Julien Rouhaud <rjuju123 () gmail ! com>
Date:       2022-01-25 15:33:19
Message-ID: 20220125153319.bw3hsdm5epfkm2j6 () jrouhaud
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Hi,

On Tue, Jan 25, 2022 at 02:42:14AM +0000, huangning290@yahoo.com wrote:
> Hi:I created a new variable-length data type, and now I want to create a GIN
> index for it. According to the rules of GIN index, I created three functions:
> extractValue, extractQuery, and compare. I made sure that the return value of
> the first two functions is the address of the array, but when using the index
> query, the GIN tuple data obtained by calling PG_GETARG_DATUM in the compare
> function is incorrect, and it is misplaced! In memory the size of the data
> header becomes something else, and the position of the first byte is not the
> header, it becomes the fourth byte. So there is a high probability that the
> function called is wrong or my return value is wrong when creating the index
> or the error is somewhere else?

It's hard to have an opinion without seeing any code extract.  Have you checked
contrib module for examples of other GIN opclasses, like pg_trgrm, or hstore
for varlena datatype with GIN support?

Note also that pgsql-hackers is probably a better mailing list for this kind of
questions.


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