DataSourceAnalysis (druid-processing 0.19.0 API)

java.lang.Object
- org.apache.druid.query.planning.DataSourceAnalysis

```
public class DataSourceAnalysis
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  <-- Possible query datasource(s) [may be none, or multiple stacked]
                             |
                             Q  <-- Base query datasource, returned by getBaseQuery() if it exists
                             |
                             J  <-- Possible join tree, expected to be left-leaning
                            / \
                           J  Dj <--  Other leaf datasources
   Base datasource        / \         which will be joined
  (bottom-leftmost) -->  Db Dj  <---- into the base datasource

 
```
The base datasource (Db) is returned by getBaseDataSource(). The other leaf datasources are returned by getPreJoinableClauses(). The outer query datasources are available as part of getDataSource(), which just returns the original datasource that was provided for analysis. 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 StorageAdapter. 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.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`equals(Object o)`
`static DataSourceAnalysis`	`forDataSource(DataSource dataSource)`
`DataSource`	`getBaseDataSource()` Returns the base (bottom-leftmost) datasource.
`Optional<Query<?>>`	`getBaseQuery()` Returns the bottommost (i.e.
`Optional<QuerySegmentSpec>`	`getBaseQuerySegmentSpec()` Returns the `QuerySegmentSpec` that is associated with the base datasource, if any.
`Optional<TableDataSource>`	`getBaseTableDataSource()` Returns the same datasource as `getBaseDataSource()`, but only if it is a table.
`DataSource`	`getDataSource()` Returns the topmost datasource: the original one passed to `forDataSource(DataSource)`.
`List<PreJoinableClause>`	`getPreJoinableClauses()` Returns join clauses corresponding to joinable leaf datasources (every leaf except the bottom-leftmost).
`int`	`hashCode()`
`boolean`	`isConcreteBased()` Returns true if this datasource can be computed by the core Druid query stack via a scan of a concrete base datasource.
`boolean`	`isConcreteTableBased()` Returns true if this datasource is concrete-based (see `isConcreteBased()`, and the base datasource is a 'table' or union of them.
`boolean`	`isGlobal()` Returns true if all servers have the ability to compute this datasource.
`boolean`	`isQuery()` Returns true if this datasource represents a subquery (that is, whether it is a `QueryDataSource`).
`String`	`toString()`

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Method Detail
  - forDataSource
```
public static DataSourceAnalysis forDataSource(DataSource dataSource)
```
  - getDataSource
```
public DataSource getDataSource()
```
    Returns the topmost datasource: the original one passed to forDataSource(DataSource).
  - getBaseDataSource
```
public DataSource getBaseDataSource()
```
    Returns the base (bottom-leftmost) datasource.
  - getBaseTableDataSource
```
public Optional<TableDataSource> getBaseTableDataSource()
```
    Returns the same datasource as getBaseDataSource(), but only if it is a table. Useful on data servers, since they generally can only handle queries where the base datasource is a table.
  - getBaseQuery
```
public Optional<Query<?>> getBaseQuery()
```
    Returns the bottommost (i.e. innermost) Query from a possible stack of outer queries at the root of the datasource tree. This is the query that will be applied to the base datasource plus any joinables that might be present.
    
    Returns:
    
    the query associated with the base datasource if isQuery() is true, else empty
  - getBaseQuerySegmentSpec
```
public Optional<QuerySegmentSpec> getBaseQuerySegmentSpec()
```
    Returns the QuerySegmentSpec that is associated with the base datasource, if any. This only happens when there is an outer query datasource. In this case, the base querySegmentSpec is the one associated with the innermost subquery. This QuerySegmentSpec is taken from the query returned by getBaseQuery().
    
    Returns:
    
    the query segment spec associated with the base datasource if isQuery() is true, else empty
  - getPreJoinableClauses
```
public List<PreJoinableClause> getPreJoinableClauses()
```
    Returns join clauses corresponding to joinable leaf datasources (every leaf except the bottom-leftmost).
  - isGlobal
```
public boolean isGlobal()
```
    Returns true if all servers have the ability to compute this datasource. These datasources depend only on globally broadcast data, like lookups or inline data or broadcast segments.
  - isConcreteBased
```
public boolean isConcreteBased()
```
    Returns true if this datasource can be computed by the core Druid query stack via a scan of a concrete base datasource. All other datasources involved, if any, must be global.
  - isConcreteTableBased
```
public boolean isConcreteTableBased()
```
    Returns true if this datasource is concrete-based (see isConcreteBased(), and the base datasource is a 'table' or union of them. This is an important property because it corresponds to datasources that can be handled by Druid data servers, like Historicals.
  - isQuery
```
public boolean isQuery()
```
    Returns true if this datasource represents a subquery (that is, whether it is a QueryDataSource).
  - 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

Class DataSourceAnalysis

Method Summary

Methods inherited from class java.lang.Object

Method Detail

forDataSource

getDataSource

getBaseDataSource

getBaseTableDataSource

getBaseQuery

getBaseQuerySegmentSpec

getPreJoinableClauses

isGlobal

isConcreteBased

isConcreteTableBased

isQuery

equals

hashCode

toString