Package org.apache.calcite.model

Class JsonLattice

java.lang.Object

org.apache.calcite.model.JsonLattice

public class JsonLattice
extends Object

Element that describes a star schema and provides a framework for defining, recognizing, and recommending materialized views at various levels of aggregation.

Occurs within JsonSchema.lattices.

See Also:

• Description of schema elements

Field Summary

Fields

Modifier and Type	Field	Description
final boolean	algorithm	Whether to use an optimization algorithm to suggest and populate an initial set of tiles.
final long	algorithmMaxMillis	Maximum time (in milliseconds) to run the algorithm.
final boolean	auto	Whether to materialize tiles on demand as queries are executed.
final List<JsonMeasure>	defaultMeasures	List of measures that a tile should have by default.
final String	name	The name of this lattice.
final @Nullable Double	rowCountEstimate	Estimated number of rows.
final Object	sql	SQL query that defines the lattice.
final @Nullable String	statisticProvider	Name of a class that provides estimates of the number of distinct values in each column.
final List<JsonTile>	tiles	List of materialized aggregates to create up front.

Constructor Summary

Constructors

Constructor	Description
JsonLattice(String name, Object sql, @Nullable Boolean auto, @Nullable Boolean algorithm, @Nullable Long algorithmMaxMillis, @Nullable Double rowCountEstimate, @Nullable String statisticProvider, @Nullable List<JsonMeasure> defaultMeasures)

Method Summary

Modifier and Type	Method	Description
void	accept(ModelHandler handler)
String	getSql()	Returns the SQL query as a string, concatenating a list of lines if necessary.
String	toString()
void	visitChildren(ModelHandler modelHandler)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

name

public final String name

The name of this lattice.

Required.

sql

public final Object sql

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.

auto

public final boolean auto

Whether to materialize tiles on demand as queries are executed.

Optional; default is true.

algorithm

public final boolean algorithm

Whether to use an optimization algorithm to suggest and populate an initial set of tiles.

Optional; default is false.

algorithmMaxMillis

public final long algorithmMaxMillis

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.

rowCountEstimate

public final @Nullable Double rowCountEstimate

Estimated number of rows.

If null, Calcite will a query to find the real value.

statisticProvider

public final @Nullable String statisticProvider

Name of a class that provides estimates of the number of distinct values in each column.

The class must implement the 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.

tiles

public final List<JsonTile> tiles

List of materialized aggregates to create up front.

defaultMeasures

public final List<JsonMeasure> defaultMeasures

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(*)".

Constructor Details

JsonLattice

public JsonLattice(String name,
 Object sql,
 @Nullable Boolean auto,
 @Nullable Boolean algorithm,
 @Nullable Long algorithmMaxMillis,
 @Nullable Double rowCountEstimate,
 @Nullable String statisticProvider,
 @Nullable List<JsonMeasure> defaultMeasures)

Method Details

accept

public void accept(ModelHandler handler)

toString

public String toString()

Overrides:

toString in class Object

getSql

public String getSql()

Returns the SQL query as a string, concatenating a list of lines if necessary.

visitChildren

public void visitChildren(ModelHandler modelHandler)