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https://issues.apache.org/jira/browse/IGNITE-23745?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aleksey Plekhanov updated IGNITE-23745:
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Summary: Calcite engine. Add ability to extend SQL engine with new system
functions/operators (was: Calcite engine. Add ability to extent SQL engine
with new system functions/operators)
> Calcite engine. Add ability to extend SQL engine with new system
> functions/operators
> ------------------------------------------------------------------------------------
>
> Key: IGNITE-23745
> URL: https://issues.apache.org/jira/browse/IGNITE-23745
> Project: Ignite
> Issue Type: Improvement
> Reporter: Aleksey Plekhanov
> Assignee: Aleksey Plekhanov
> Priority: Major
> Labels: calcite, ise
>
> Old H2-based SQL engine has a lot of functions and operators, which are
> currently not supported by Calcite-based SQL engine. Some of these
> functions/operators have another syntax and duplicating it just to provide
> compatibility is not a good idea. For example, there is a function
> {{SUBSTR(a, b, c)}}, supported by H2-engine and not supported by
> Calcite-engine. Instead Calcite-engine supports {{SUBSTRING}} function (also
> described by SQL standard). Adding {{SUBSTR}} to the Calcite-engine will lead
> to overloading functions list with duplicates. User defined functions can't
> fully cover all features that Calcite has to implement system functions. So,
> it's proposed to add an ability to implement new system functions by plugins
> or extensions.
> I see several points of extension on different stages of query execution:
> * {{IgniteStdSqlOperatorTable}} - a table of operators which can be used by
> SQL engine. We already have public method {{register}} here.
> * {{IgniteSqlCallRewriteTable}} - a table of rewriters for operators (before
> validation, SqlNode to SqlNode). We already have public methid {{register}}
> here too.
> * IgniteConvertletTable - a table of convertlet (validated SqlNode to
> RexNode). Protected methods {{registerOp}} and {{addAlias}} can be converted
> to public.
> * {{RexImpTable}} - a table of implementors (RexNode to Expression). Here we
> have some private methods (all they just register implementor in {{map}}),
> and a set of predefined implementors, some of them can be converted to public.
> * {{Accumulators}} - a table of aggregate functions. Refactoring required
> here. Currently the list of aggregate functions is hardcoded with switch/case
> block. (Perhaps we can fix {{Accumulators}} by another ticket).
> Also, it will be useful to somehow extend grammer, but I see no simple way
> how to do it right now.
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