org.apache.flink.table.sources

Interface FilterableTableSource<T>

All Known Implementing Classes:

FileSystemTableSource, OrcTableSource, ParquetTableSource

public interface FilterableTableSource<T>

Adds support for filtering push-down to a TableSource. A TableSource extending this interface is able to filter records before returning.

Method Summary

Modifier and Type	Method and Description
TableSource<T>	applyPredicate(List<Expression> predicates) Check and pick all predicates this table source can support.
boolean	isFilterPushedDown() Return the flag to indicate whether filter push down has been tried.

Method Detail

applyPredicate

TableSource<T> applyPredicate(List<Expression> predicates)

Check and pick all predicates this table source can support. The passed in predicates have been translated in conjunctive form, and table source can only pick those predicates that it supports.

WARNING: Flink planner will push down PlannerExpressions (which are defined in flink-table-planner module), while Blink planner will push down Expressions. So the implementation for Flink planner and Blink planner should be different and incompatible. PlannerExpression will be removed in the future.

After trying to push predicates down, we should return a new TableSource instance which holds all pushed down predicates. Even if we actually pushed nothing down, it is recommended that we still return a new TableSource instance since we will mark the returned instance as filter push down has been tried.

We also should note to not changing the form of the predicates passed in. It has been organized in CNF conjunctive form, and we should only take or leave each element from the list. Don't try to reorganize the predicates if you are absolutely confident with that.

Parameters:

predicates - A list contains conjunctive predicates, you should pick and remove all expressions that can be pushed down. The remaining elements of this list will further evaluated by framework.

Returns:

A new cloned instance of TableSource with or without any filters been pushed into it.

isFilterPushedDown

boolean isFilterPushedDown()

Return the flag to indicate whether filter push down has been tried. Must return true on the returned instance of applyPredicate(java.util.List<org.apache.flink.table.expressions.Expression>).