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  1. MariaDB Server
  2. MDEV-20837

Add MariaDB_FUNCTION_PLUGIN

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      Description

      Originally, Serg and Bar decided to implement function plugins through MariaDB_FUNCTION_COLLECTION_PLUGIN, so a plugin can export multiple SQL functions at the same type.
      The retionale of this solution was to avoid flooding the output of this query:

      SELECT * FROM INFORMATION_SCHEMA.PLUGINS;
      

      For example, we have 155 GEOMETRY related functions. Exporting all 155 function as individual plugins would add 155 entries to the query output.

      After adding MariaDB_FUNCTION_COLLECTION_PLUGIN, we came up to the following:

      • The hash to lookup functions by name appeared to be redundant. We already have a hash to lookup plugins by name (and type). So this new hash looked really duplicate.
      • It's not possible to maintain ref_count of individual functions. So some more code duplication is needed for dynamic plugins, to maintain reference counters.

      After discussing, Serg and Bar decided that:

      • For now we should go through a new plugin type, MariaDB_FUNCTION_PLUGIN, where each plugin exports a single function. We'll do flood the output of INFORMATION_SCHEMA.PLUGINS queries for now, but this is tolerable. It's more important to avoid code duplication.
      • Eventually we'll add generic collection plugins with these characteristics:
        • A generic collection plugin will be able to join multiple plugins, even of different types (e.g. a number of MariaDB_DATE_TYPE_PLUGINs and MariaDB_FUNCTION_PLUGINs) into a single instance, which will be available in some INFORMATION_SCHEMA table (either PLUGINS, or a new one) as a single record.
        • A generic collection plugin will be able to do atomic initialization: either load all sub-plugins, or load non of them.

      Under terms of this task we do the following:

      • Implement MariaDB_FUNCTION_PLUGIN, to export individual functions.
      • Change the code in /plugins/type_inet/ and /plugins/type_test/ to use MariaDB_FUNCTION_PLUGIN instead of MariaDB_FUNCTION_COLLECTION_PLUGIN.
      • Remove MariaDB_FUNCTION_COLLECTION.

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              Assignee:
              serg Sergei Golubchik
              Reporter:
              bar Alexander Barkov
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