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https://issues.apache.org/jira/browse/CALCITE-4979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17473191#comment-17473191
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Julian Bright commented on CALCITE-4979:
----------------------------------------
Thanks, I've added the code block so it should be readable, yes I've added
PREDICT as keyword, and am using SqlKind.Other for now (although potentially it
could be useful to have a new SqlKind.Predict in future to include the GIVEN
keyword too)
> Add support for extending parser to support additional select statements
> ------------------------------------------------------------------------
>
> Key: CALCITE-4979
> URL: https://issues.apache.org/jira/browse/CALCITE-4979
> Project: Calcite
> Issue Type: New Feature
> Components: extensions
> Affects Versions: 1.29.0
> Environment: * mac-arm64
> Reporter: Julian Bright
> Priority: Minor
>
> Calcite currently supports [extending the
> parser]([https://calcite.apache.org/docs/adapter.html#extending-the-parser)]
> with `config.fmpp` that has sections statements including alter and drop.
> I require the ability to introduce a custom `SELECT` like statement which
> requires adding adding an additional clause to the LeafQuery syntax in the
> `Parser.jj` file eg:
> {code}
> /**
> * Parses a leaf in a query expression (SELECT, VALUES or TABLE).
> */
> SqlNode LeafQuery(ExprContext exprContext) :
> {
> SqlNode e;
> }
> {
> {
> // ensure a query is legal in this context
> checkQueryExpression(exprContext);
> }
> e = SqlSelect() { return e; }
> |
> <#-- Add methods to parse additional select statements here -->
> <#list
> (parser.selectStatementParserMethods!default.parser.selectStatementParserMethods)
> as method>
> e = ${method} { return e; }
> |
> </#list>
> e = TableConstructor() { return e; }
> |
> e = ExplicitTable(getPos()) { return e; }
> }
> {code}
> I would like to add a new section `selectStatementParserMethods` to the
> config eg:
> {code}
> # List of methods for parsing custom select statements.
> # Return type of method implementation should be 'SqlNode'.
> # Example: SqlSelect()
> selectStatementParserMethods: [
> ]
> {code}
> Files required to be updated main codegen are:
> * core/src/main/codegen/templates/Parser.jj
> * core/src/main/codegen/default_config.fmpp
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