backend_flush_after bytes/pages

Hi,

On 2017-02-07 19:40:45 +0100, Дилян Палаузов wrote:

doc/src/smgl/config.sgml: line 2049 for postgres 9.6 states: "Whenever more than backend_flush_after bytes have been written...", which suggests that the data is interpreted as bytes. However the by initdb generated postgresql.conf file mentions that backend_flush_after is in pages, and pg_settings says the unit is 8kB.

Please rephrase doc/src/smgl/config.sgml to state, that the unit for
backend_flush_after is not bytes, but pages.

You can configure it in bytes though, so I don't really think that
matters?

Regards,

Andres

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Hello,

does
backend_flush_after = 7
mean 7 bytes or seven pages? https://www.postgresql.org/docs/9.6/static/runtime-config-resource.html#GUC-BACKEND-FLUSH-AFTER suggests it means 7 bytes, which is not the reality. The documentation is misleading.

Greetings
Dilian

On 02/07/17 19:57, Andres Freund wrote:

Hi,

On 2017-02-07 19:40:45 +0100, Дилян Палаузов wrote:

doc/src/smgl/config.sgml: line 2049 for postgres 9.6 states: "Whenever more than backend_flush_after bytes have been written...", which suggests that the data is interpreted as bytes. However the by initdb generated postgresql.conf file mentions that backend_flush_after is in pages, and pg_settings says the unit is 8kB.

Please rephrase doc/src/smgl/config.sgml to state, that the unit for
backend_flush_after is not bytes, but pages.

You can configure it in bytes though, so I don't really think that
matters?

Regards,

Andres

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Hi,

(please don't top-quote on this list)

On 2017-02-07 20:21:58 +0100, Дилян Палаузов wrote:

does
backend_flush_after = 7
mean 7 bytes or seven pages? https://www.postgresql.org/docs/9.6/static/runtime-config-resource.html#GUC-BACKEND-FLUSH-AFTER suggests it means 7 bytes, which is not the reality. The documentation is misleading.

7 pages. But if you write '700kB' it'll be taken as bytes (with 8kB
granularity). shared_buffers also is computed based on page-size and
documented in bytes.

Regards,

Andres

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