Thread: BUG #16835: btree index does not work for where clause using 'foo%'

BUG #16835: btree index does not work for where clause using 'foo%'

From

PG Bug reporting form

Date:

22 January 2021, 15:56:52

The following bug has been logged on the website:

Bug reference:      16835
Logged by:          Hongyan (Heather) Zhang
Email address:      zhangh3@aetna.com
PostgreSQL version: 11.9
Operating system:   aurora postgres 11
Description:

https://www.postgresql.org/docs/11/indexes-types.html, according to this
page, btree index is supposed to work for where clause col like 'foo%', but
does not work for me. we are on aurora postgres 11, I also tested on
postgres 11, it does not work either.

Re: BUG #16835: btree index does not work for where clause using 'foo%'

From

Tom Lane

Date:

22 January 2021, 16:44:03

PG Bug reporting form <noreply@postgresql.org> writes:
> https://www.postgresql.org/docs/11/indexes-types.html, according to this
> page, btree index is supposed to work for where clause col like 'foo%', but
> does not work for me. we are on aurora postgres 11, I also tested on
> postgres 11, it does not work either.

As the manual explains, that will not work by default unless your
database locale is C (which is an uncommon default nowadays).

It's also possible that Aurora has changed something that keeps
it from working, but I'd investigate the locale angle first.

            regards, tom lane

Re: [EXTERNAL] Re: BUG #16835: btree index does not work for where clause using 'foo%'

From

"Zhang, Hongyan"

Date:

22 January 2021, 19:07:22

Thanks, Tom.

Locale is en_US.UTF-8.

Is there plan to alter that behavior to allow index in non C locale?

From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Friday, January 22, 2021 at 10:52 AM
To: "Zhang, Hongyan" <ZhangH3@aetna.com>
Cc: "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
Subject: [EXTERNAL] Re: BUG #16835: btree index does not work for where clause using 'foo%'

**** External Email - Use Caution ****

PG Bug reporting form <noreply@postgresql.org> writes:
> https://www.postgresql.org/docs/11/indexes-types.html, according to this
> page, btree index is supposed to work for where clause col like 'foo%', but
> does not work for me. we are on aurora postgres 11, I also tested on
> postgres 11, it does not work either.

As the manual explains, that will not work by default unless your
database locale is C (which is an uncommon default nowadays).

It's also possible that Aurora has changed something that keeps
it from working, but I'd investigate the locale angle first.

regards, tom lane

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Thank you, Aetna

Re: [EXTERNAL] Re: BUG #16835: btree index does not work for where clause using 'foo%'

From

luis.roberto@siscobra.com.br

Date:

22 January 2021, 19:23:37

De: "Zhang, Hongyan" <ZhangH3@aetna.com>
Para: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: "pgsql-bugs" <pgsql-bugs@lists.postgresql.org>
Enviadas: Sexta-feira, 22 de janeiro de 2021 16:07:22
Assunto: Re: [EXTERNAL] Re: BUG #16835: btree index does not work for where clause using 'foo%'

.style1 {font-family: "Times New Roman";}

Thanks, Tom.

Locale is en_US.UTF-8.

Is there plan to alter that behavior to allow index in non C locale?

According to documentation: "However, if your database does not use the C locale you will need to create the index with a special operator class to support indexing of pattern-matching queries;"

So you'll have to create the index with a specific operator class.

You can use:.

CREATE INDEX tbl_col_text_pattern_ops_idx ON tbl(col text_pattern_ops) [1]

[1] https://stackoverflow.com/questions/1566717/postgresql-like-query-performance-variations

Re: [EXTERNAL] Re: BUG #16835: btree index does not work for where clause using 'foo%'

From

"Zhang, Hongyan"

Date:

22 January 2021, 19:45:53

Thanks, Luis

From: "luis.roberto@siscobra.com.br" <luis.roberto@siscobra.com.br>
Date: Friday, January 22, 2021 at 1:28 PM
To: "Zhang, Hongyan" <ZhangH3@aetna.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-bugs <pgsql-bugs@lists.postgresql.org>
Subject: Re: [EXTERNAL] Re: BUG #16835: btree index does not work for where clause using 'foo%'

**** External Email - Use Caution ****

Thanks, Tom.

Locale is en_US.UTF-8.

Is there plan to alter that behavior to allow index in non C locale?

According to documentation: "However, if your database does not use the C locale you will need to create the index with a special operator class to support indexing of pattern-matching queries;"

So you'll have to create the index with a specific operator class.

You can use:.

CREATE INDEX tbl_col_text_pattern_ops_idx ON tbl(col text_pattern_ops) [1]

[1] https://stackoverflow.com/questions/1566717/postgresql-like-query-performance-variations