org.apache.drill.exec.ops

Class ViewExpansionContext

java.lang.Object

org.apache.drill.exec.ops.ViewExpansionContext

public class ViewExpansionContext
extends Object

Contains context information about view expansion(s) in a query. Part of .QueryContext. Before expanding a view into its definition, as part of the DrillViewTable.toRel(org.apache.calcite.plan.RelOptTable.ToRelContext, org.apache.calcite.plan.RelOptTable), first a ViewExpansionContext.ViewExpansionToken is requested from ViewExpansionContext through reserveViewExpansionToken(String). Once view expansion is complete, a token is released through ViewExpansionContext.ViewExpansionToken.release(). A view definition itself may contain zero or more views for expanding those nested views also a token is obtained. Ex: Following are the available view tables: { "view_1", "view_2", "view_3", "view_4" }. Corresponding owners are {"view1Owner", "view2Owner", "view3Owner", "view4Owner"}. Definition of "view4" : "SELECT field4 FROM view3" Definition of "view3" : "SELECT field4, field3 FROM view2" Definition of "view2" : "SELECT field4, field3, field2 FROM view1" Definition of "view1" : "SELECT field4, field3, field2, field1 FROM someTable" Query is: "SELECT * FROM view4". Steps: 1. "view4" comes for expanding it into its definition 2. A token "view4Token" is requested through reserveViewExpansionToken(String view4Owner) 3. "view4" is called for expansion. As part of it 3.1 "view3" comes for expansion 3.2 A token "view3Token" is requested through reserveViewExpansionToken(String view3Owner) 3.3 "view3" is called for expansion. As part of it 3.3.1 "view2" comes for expansion 3.3.2 A token "view2Token" is requested through reserveViewExpansionToken(String view2Owner) 3.3.3 "view2" is called for expansion. As part of it 3.3.3.1 "view1" comes for expansion 3.3.3.2 A token "view1Token" is requested through reserveViewExpansionToken(String view1Owner) 3.3.3.3 "view1" is called for expansion 3.3.3.4 "view1" expansion is complete 3.3.3.5 Token "view1Token" is released 3.3.4 "view2" expansion is complete 3.3.5 Token "view2Token" is released 3.4 "view3" expansion is complete 3.5 Token "view3Token" is released 4. "view4" expansion is complete 5. Token "view4Token" is released.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	ViewExpansionContext.ViewExpansionToken Represents token issued to a view owner for expanding the view.

Constructor Summary

Constructors

Constructor and Description
ViewExpansionContext(DrillConfig config, SchemaConfig.SchemaConfigInfoProvider schemaConfigInfoProvider)
ViewExpansionContext(QueryContext queryContext)

Method Summary

Modifier and Type	Method and Description
boolean	isImpersonationEnabled()
ViewExpansionContext.ViewExpansionToken	reserveViewExpansionToken(String viewOwner) Reserve a token for expansion of view owned by given user name.

Methods inherited from class java.lang.Object

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

Constructor Detail

ViewExpansionContext

public ViewExpansionContext(QueryContext queryContext)

ViewExpansionContext

public ViewExpansionContext(DrillConfig config,
                            SchemaConfig.SchemaConfigInfoProvider schemaConfigInfoProvider)

Method Detail

isImpersonationEnabled

public boolean isImpersonationEnabled()

reserveViewExpansionToken

public ViewExpansionContext.ViewExpansionToken reserveViewExpansionToken(String viewOwner)

Reserve a token for expansion of view owned by given user name. If it can't issue any more tokens, throws UserException.

Parameters:

viewOwner - Name of the user who owns the view.

Returns:

An instance of ViewExpansionContext.ViewExpansionToken which must be released when done using the token.