From: Vladislav Shpilevoy <v.shpilevoy@tarantool.org> To: Chris Sosnin <k.sosnin@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: Re: [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings Date: Mon, 10 Feb 2020 23:09:11 +0100 [thread overview] Message-ID: <d01a2df7-249a-1bba-20a8-22e06998d5f0@tarantool.org> (raw) In-Reply-To: <FBA2C2CA-0314-45FF-BD7D-BC2DBEEA322C@tarantool.org> Hi! Thanks for the fixes! On the branch you said this commit is 'Part of #4711'. Why not 'Closes #4711'? What else is left? > sql: provide a user friendly frontend for accessing session settings > > Currently if a user wants to change session setting with sql, he has > to execute non-obvious query, thus, we introduce a more native way to > do this. > > Part of #4711 > > @TarantoolBot document > Title: API for accessing _session_settings space. > There are two ways of updating values of session settings: > via Lua and SQL. > > Lua: > box.session.settings is a table, which is accessible right after > session creation. The syntax is the following: Lets say it is available always. Because a user can't live without a session anyway. It always exists for a user. > `box.session.settings.<setting_name>:set(<new_value>)`. > > Example of usage: > ``` > tarantool> box.session.settings.sql_default_engine > --- > - memtx > ... > > tarantool> box.session.settings.sql_default_engine:set('vinyl') > --- > ... > > ``` > > The table itself represents the (unordered) result of select > from _session_settings space. Every setting is implemented as > a table, so there is no way to retrieve an actual value and use > it until :get() method is introduced. > > SQL: > Instead of typing long UPDATE query one can use the SET statement: > `box.execute([[SET "<setting_name>" = <new_value>]])`. > Note, that this query is case sensitive so the name must be quoted. > > Example: > ``` > tarantool> box.execute([[set "sql_default_engine" = 'memtx']]) > --- > - row_count: 1 > ... > > tarantool> box.execute([[set "sql_defer_foreign_keys" = true]]) > --- > - row_count: 1 > ... > > ``` I am not so sure about binary search anymore. I just found another probably much faster way - perfect hash function. There is a GNU tool 'gperf' to generate C code for a given keyset with hash calculation and search functions. I fed our settings to it and obtained not so scary result. File: test.gperf %% sql_default_engine sql_defer_foreign_keys sql_full_column_names sql_full_metadata sql_parser_debug sql_recursive_triggers sql_reverse_unordered_selects sql_select_debug sql_vdbe_debug %% Command: gperf test.gperf > test.c The test.c file is 122 lines long including some {}, useless checks, macros, and comments. It could easily be compacted a lot. This is probably overkill though. It needs to be completely regenerated each time when the keyset is changed, consumes more static memory. The patchset LGTM. I propose to send it to Nikita on a second review.
next prev parent reply other threads:[~2020-02-10 22:09 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-30 11:10 [Tarantool-patches] [PATCH] " Chris Sosnin 2020-02-03 22:17 ` Vladislav Shpilevoy 2020-02-04 19:32 ` [Tarantool-patches] [PATCH 4/4] " Chris Sosnin 2020-02-06 22:16 ` Vladislav Shpilevoy 2020-02-07 9:40 ` Chris Sosnin 2020-02-10 22:09 ` Vladislav Shpilevoy [this message] 2020-02-17 11:46 ` Chris Sosnin 2020-02-17 11:56 ` Nikita Pettik 2020-02-17 12:12 [Tarantool-patches] [PATCH 0/4] box: session settings fixes Chris Sosnin 2020-02-17 12:12 ` [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings Chris Sosnin 2020-03-16 17:02 ` Nikita Pettik 2020-03-16 22:53 ` Vladislav Shpilevoy 2020-03-17 17:26 ` Chris Sosnin 2020-03-17 20:12 ` Nikita Pettik 2020-03-17 21:00 ` Chris Sosnin 2020-03-18 10:00 ` Chris Sosnin 2020-03-30 9:13 [Tarantool-patches] [PATCH 0/4] session settings fixes Chris Sosnin 2020-03-30 9:13 ` [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings Chris Sosnin 2020-04-03 15:19 ` Nikita Pettik 2020-04-04 21:56 ` Vladislav Shpilevoy 2020-04-10 15:40 ` Chris Sosnin 2020-04-11 17:18 ` Vladislav Shpilevoy 2020-04-13 7:50 ` Timur Safin
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