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https://issues.apache.org/jira/browse/CALCITE-436?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde resolved CALCITE-436.
---------------------------------
Resolution: Fixed
Fix Version/s: 0.9.2-incubating
Fixed in
http://git-wip-us.apache.org/repos/asf/incubator-calcite/commit/263640ff.
> Simpler SPI to query Table
> --------------------------
>
> Key: CALCITE-436
> URL: https://issues.apache.org/jira/browse/CALCITE-436
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Fix For: 0.9.2-incubating
>
>
> Currently, the easiest way for a Table to return results is to implement
> TranslatableTable, and in the toRel method return a RelNode. That RelNode is
> typically a sub-class of TableAccessRelBase and implements itself by
> generating Java code, which must be compiled an executed.
> We propose an interfaces so that a Table can return results directly.
> {code}
> import net.hydromatic.avatica.Cursor;
> import org.eigenbase.util.Pair;
> import net.hydromatic.optiq.Table;
> import org.eigenbase.rex.RexNode;
> import org.eigenbase.reltype.RelDataTypeField;
> interface CursorableTable extends Table {
> /** Returns a cursor over the rows in this Table. */
> Cursor scan();
> }
> interface ProjectableCursorableTable extends Table {
> /** Given a list of filters and a list of fields to project, returns a
> * cursor over the rows in this Table and a list of filters that it
> * could not implement.
> *
> * <p>The cursor must implement the projects and any filters not
> * in the list. */
> Pair<Cursor, List<RexNode>> projectFilterScan(List<RexNode> filters,
> List<RelDataTypeField> projects);
> }
> {code}
> Cursor is a simple API to implement.
> A table that implements the CursorableTable SPI does not need to implement
> TranslatableTable, and so can return its results without doing any code
> generation.
> The ProjectableCursorableTable SPI is also optional and goes further; it
> allows Calcite to push down simple projects and filters without the Table
> implementor writing any rules or code-generation code. If the implementation
> of the SPI cannot handle a particular filter, it just returns it, and Calcite
> will add its own filter to implement it.
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