Package org.apache.druid.query.planning

Class JoinDataSourceAnalysis

java.lang.Object

org.apache.druid.query.planning.JoinDataSourceAnalysis

public class JoinDataSourceAnalysis
extends Object

Analysis of a datasource for purposes of deciding how to execute a particular query. The analysis breaks a datasource down in the following way:

                             Q  invalid input: '<'-- Possible query datasource(s) [may be none, or multiple stacked]
                             |
                             Q  invalid input: '<'-- Base query datasource, returned by 

invalid reference
#getBaseQuery()

 if it exists
                             |
                             J  invalid input: '<'-- Possible join tree, expected to be left-leaning
                            / \
                           J  Dj invalid input: '<'--  Other leaf datasources
   Base datasource        / \         which will be joined
  (bottom-leftmost) -->  Db Dj  invalid input: '<'---- into the base datasource

 

The base datasource (Db) is returned by getBaseDataSource(). The other leaf datasources are returned by getPreJoinableClauses(). The base datasource (Db) will never be a join, but it can be any other type of datasource (table, query, etc). Note that join trees are only flattened if they occur at the top of the overall tree (or underneath an outer query), and that join trees are only flattened to the degree that they are left-leaning. Due to these facts, it is possible for the base or leaf datasources to include additional joins. The base datasource is the one that will be considered by the core Druid query stack for scanning via Segment and CursorFactory. The other leaf datasources must be joinable onto the base data. The idea here is to keep things simple and dumb. So we focus only on identifying left-leaning join trees, which map neatly onto a series of hash table lookups at query time. The user/system generating the queries, e.g. the druid-sql layer (or the end user in the case of native queries), is responsible for containing the smarts to structure the tree in a way that will lead to optimal execution.

Constructor Summary

Constructors

Constructor	Description
JoinDataSourceAnalysis(DataSource baseDataSource, Query<?> baseQuery, DimFilter joinBaseTableFilter, List<PreJoinableClause> preJoinableClauses, QuerySegmentSpec querySegmentSpec)

Method Summary

Modifier and Type	Method	Description
static JoinDataSourceAnalysis	constructAnalysis(JoinDataSource dataSource)
boolean	equals(Object o)
DataSource	getBaseDataSource()	Returns the base (bottom-leftmost) datasource.
Optional<DimFilter>	getJoinBaseTableFilter()	If the original data source is a join data source and there is a DimFilter on the base table data source, that DimFilter is returned here
List<PreJoinableClause>	getPreJoinableClauses()	Returns join clauses corresponding to joinable leaf datasources (every leaf except the bottom-leftmost).
int	hashCode()
boolean	isBaseColumn(String column)	Returns whether "column" on the analyzed datasource refers to a column from the base datasource.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Details

JoinDataSourceAnalysis

public JoinDataSourceAnalysis(DataSource baseDataSource,
 @Nullable
 Query<?> baseQuery,
 @Nullable
 DimFilter joinBaseTableFilter,
 List<PreJoinableClause> preJoinableClauses,
 @Nullable
 QuerySegmentSpec querySegmentSpec)

Method Details

getBaseDataSource

public DataSource getBaseDataSource()

Returns the base (bottom-leftmost) datasource.

getJoinBaseTableFilter

public Optional<DimFilter> getJoinBaseTableFilter()

If the original data source is a join data source and there is a DimFilter on the base table data source, that DimFilter is returned here

getPreJoinableClauses

public List<PreJoinableClause> getPreJoinableClauses()

Returns join clauses corresponding to joinable leaf datasources (every leaf except the bottom-leftmost).

isBaseColumn

public boolean isBaseColumn(String column)

Returns whether "column" on the analyzed datasource refers to a column from the base datasource.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

constructAnalysis

public static JoinDataSourceAnalysis constructAnalysis(JoinDataSource dataSource)