org.apache.calcite.model.JsonLattice 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.model;
import java.util.ArrayList;
import java.util.List;
/**
* Element that describes a star schema and provides a framework for defining,
* recognizing, and recommending materialized views at various levels of
* aggregation.
*
* Occurs within {@link JsonSchema#lattices}.
*
* @see JsonRoot Description of schema elements
*/
public class JsonLattice {
/** The name of this lattice.
*
*
Required.
*/
public String name;
/** SQL query that defines the lattice.
*
*
Must be a string or a list of strings (which are concatenated into a
* multi-line SQL string, separated by newlines).
*
*
The structure of the SQL statement, and in particular the order of
* items in the FROM clause, defines the fact table, dimension tables, and
* join paths for this lattice.
*/
public Object sql;
/** Whether to materialize tiles on demand as queries are executed.
*
*
Optional; default is true.
*/
public boolean auto = true;
/** Whether to use an optimization algorithm to suggest and populate an
* initial set of tiles.
*
*
Optional; default is false.
*/
public boolean algorithm = false;
/** Maximum time (in milliseconds) to run the algorithm.
*
*
Optional; default is -1, meaning no timeout.
*
*
When the timeout is reached, Calcite uses the best result that has
* been obtained so far.
*/
public long algorithmMaxMillis = -1;
/** Estimated number of rows.
*
*
If null, Calcite will a query to find the real value. */
public Double rowCountEstimate;
/** Name of a class that provides estimates of the number of distinct values
* in each column.
*
*
The class must implement the
* {@link org.apache.calcite.materialize.LatticeStatisticProvider} interface.
*
*
Or, you can use a class name plus a static field, for example
* "org.apache.calcite.materialize.Lattices#CACHING_SQL_STATISTIC_PROVIDER".
*
*
If not set, Calcite will generate and execute a SQL query to find the
* real value, and cache the results. */
public String statisticProvider;
/** List of materialized aggregates to create up front. */
public final List tiles = new ArrayList<>();
/** List of measures that a tile should have by default.
*
* A tile can define its own measures, including measures not in this list.
*
*
Optional. The default list is just "count(*)".
*/
public List defaultMeasures;
public void accept(ModelHandler handler) {
handler.visit(this);
}
@Override public String toString() {
return "JsonLattice(name=" + name + ", sql=" + getSql() + ")";
}
/** Returns the SQL query as a string, concatenating a list of lines if
* necessary. */
public String getSql() {
return toString(sql);
}
/** Converts a string or a list of strings to a string. The list notation
* is a convenient way of writing long multi-line strings in JSON. */
static String toString(Object o) {
return o == null ? null
: o instanceof String ? (String) o
: concatenate((List) o);
}
/** Converts a list of strings into a multi-line string. */
private static String concatenate(List list) {
final StringBuilder buf = new StringBuilder();
for (Object o : list) {
if (!(o instanceof String)) {
throw new RuntimeException(
"each element of a string list must be a string; found: " + o);
}
buf.append((String) o);
buf.append("\n");
}
return buf.toString();
}
public void visitChildren(ModelHandler modelHandler) {
for (JsonMeasure jsonMeasure : defaultMeasures) {
jsonMeasure.accept(modelHandler);
}
for (JsonTile jsonTile : tiles) {
jsonTile.accept(modelHandler);
}
}
}
// End JsonLattice.java