org.apache.calcite.materialize.SqlStatisticProvider Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.calcite.materialize;
import org.apache.calcite.plan.RelOptTable;
import java.util.List;
/**
* Estimates row counts for tables and columns, and whether combinations of
* columns form primary/unique and foreign keys.
*
* Unlike {@link LatticeStatisticProvider}, works on raw tables and columns
* and does not need a {@link Lattice}.
*
*
It uses {@link org.apache.calcite.plan.RelOptTable} because that contains
* enough information to generate and execute SQL, while not being tied to a
* lattice.
*
*
The main implementation,
* {@link org.apache.calcite.statistic.QuerySqlStatisticProvider}, executes
* queries on a populated database. Implementations that use database statistics
* (from {@code ANALYZE TABLE}, etc.) and catalog information (e.g. primary and
* foreign key constraints) would also be possible.
*/
public interface SqlStatisticProvider {
/** Returns an estimate of the number of rows in {@code table}. */
double tableCardinality(RelOptTable table);
/** Returns whether a join is a foreign key; that is, whether every row in
* the referencing table is matched by at least one row in the referenced
* table.
*
*
For example, {@code isForeignKey(EMP, [DEPTNO], DEPT, [DEPTNO])}
* returns true.
*
*
To change "at least one" to "exactly one", you also need to call
* {@link #isKey}. */
boolean isForeignKey(RelOptTable fromTable, List fromColumns,
RelOptTable toTable, List toColumns);
/** Returns whether a collection of columns is a unique (or primary) key.
*
* For example, {@code isKey(EMP, [DEPTNO]} returns true;
*
For example, {@code isKey(DEPT, [DEPTNO]} returns false. */
boolean isKey(RelOptTable table, List columns);
}
// End SqlStatisticProvider.java