nz.co.gregs.dbvolution.internal.querygraph

Class QueryGraph

java.lang.Object

nz.co.gregs.dbvolution.internal.querygraph.QueryGraph

public class QueryGraph
extends Object

A class to create a network of all the classes used in a query, using foreign keys and other relationships.

A undirected, possibly-cyclic, database-agnostic, graph of DBRow nodes connected by bi-directional edges created from known foreign keys and the expressions used in the query.

This class is used to identify cartesian joins by establishing which tables are included in the join, and which are not. If any node cannot be reached by traversing the graph, a AccidentalCartesianJoinException may be thrown during querying.

Ignored foreign keys are not included as edges.

DBRows returned by DBExpression.getTablesInvolved() will be used to creates edges from expressions in the query.

Support DBvolution at Patreon

Author:

Gregory Graham

Constructor Summary

Constructors

Constructor and Description
QueryGraph(List<DBRow> allQueryTables, List<BooleanExpression> expressions) Create a graph of the tables and connections for all the DBRows and BooleanExpressions provided.

Method Summary

Methods

Modifier and Type	Method and Description
void	addAndConnectToRelevant(List<DBRow> otherTables, List<BooleanExpression> expressions) Add the provided DBRows/tables and expressions to this QueryGraph, generating new nodes and edges as required.
void	addAndConnectToRelevant(List<DBRow> otherTables, List<BooleanExpression> expressions, boolean requiredTables) Add the provided DBRows/tables and expressions to this QueryGraph, generating new nodes and edges as required.
void	addOptionalAndConnectToRelevant(List<DBRow> otherTables, List<BooleanExpression> expressions) Add the provided DBRows/tables and expressions to this QueryGraph, generating new nodes and edges as required.
QueryGraph	clear() Removes all state and prepares the graph for re-initialization.
edu.uci.ics.jung.graph.Graph<QueryGraphNode,DBExpression>	getJungGraph() Create a Jung graph of this QueryGraph for display purposes.
List<DBRow>	toList() Return tables in the QueryGraph as a list.
List<DBRow>	toListIncludingCartesian() Return all tables in the QueryGraph as a list.
List<DBRow>	toListIncludingCartesianReversable(Boolean reverse) Return all tables in the QueryGraph as a list.
List<DBRow>	toListReversable(boolean reversed) Return tables in the QueryGraph as a list.
boolean	willCreateCartesianJoin() Scans the QueryGraph to detect disconnected DBRows/tables and returns TRUE if a disconnection exists.
boolean	willCreateFullOuterJoin() Scans the QueryGraph to detect full outer join.

Methods inherited from class java.lang.Object

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

Constructor Detail

QueryGraph

public QueryGraph(List<DBRow> allQueryTables,
          List<BooleanExpression> expressions)

Create a graph of the tables and connections for all the DBRows and BooleanExpressions provided.

Parameters:

allQueryTables -

expressions -

Method Detail

clear

public QueryGraph clear()

Removes all state and prepares the graph for re-initialization.

Support DBvolution at Patreon

Returns:

this QueryGraph.

addAndConnectToRelevant

public final void addAndConnectToRelevant(List<DBRow> otherTables,
                           List<BooleanExpression> expressions)

Add the provided DBRows/tables and expressions to this QueryGraph, generating new nodes and edges as required.

Parameters:

otherTables -

expressions -

addOptionalAndConnectToRelevant

public final void addOptionalAndConnectToRelevant(List<DBRow> otherTables,
                                   List<BooleanExpression> expressions)

Add the provided DBRows/tables and expressions to this QueryGraph, generating new nodes and edges as required.

The DBrows/tables will be added as optional (that is "outer join" tables) and displayed as such.

Parameters:

otherTables -

expressions -

addAndConnectToRelevant

public final void addAndConnectToRelevant(List<DBRow> otherTables,
                           List<BooleanExpression> expressions,
                           boolean requiredTables)

Add the provided DBRows/tables and expressions to this QueryGraph, generating new nodes and edges as required.

The DBrows/tables will be added as optional (that is "outer join" tables) if requiredTables is FALSE.

Parameters:

otherTables -

expressions -

requiredTables -

willCreateCartesianJoin

public boolean willCreateCartesianJoin()

Scans the QueryGraph to detect disconnected DBRows/tables and returns TRUE if a disconnection exists.

Support DBvolution at Patreon

Returns:

TRUE if the current graph contains a discontinuity which will cause a cartesian join to occur.

willCreateFullOuterJoin

public boolean willCreateFullOuterJoin()

Scans the QueryGraph to detect full outer join.

Support DBvolution at Patreon

Returns:

TRUE contains only optional tables, FALSE otherwise.

toList

public List<DBRow> toList()

Return tables in the QueryGraph as a list.

Starting from a semi-random table (see getStartTable()) traverse the graph and add all nodes found to the list.

This method does not check for discontinuities. If there is a cartesian join/discontinuity present only some of the nodes will be returned. Use toListIncludingCartesian() if you need to span a discontinuity.

Some optimization is attempted, by trying to include all the required/inner tables first before adding the optional/outer tables. This avoids a common problem of a query that spans the intersection of 2 optional/outer tables, creating mid-query cartesian join that could have been avoided by including a related required/inner table first.

Support DBvolution at Patreon

Returns:

a list of all DBRows in this QueryGraph in a smart an order as possible.

toListReversable

public List<DBRow> toListReversable(boolean reversed)

Return tables in the QueryGraph as a list.

Starting from a semi-random table (see getStartTable()) traverse the graph and add all nodes found to the list.

This method does not check for discontinuities. If there is a cartesian join/discontinuity present only some of the nodes will be returned. Use toListIncludingCartesian() if you need to span a discontinuity.

Some optimization is attempted, by trying to include all the required/inner tables first before adding the optional/outer tables. This avoids a common problem of a query that spans the intersection of 2 optional/outer tables, creating mid-query cartesian join that could have been avoided by including a related required/inner table first.

Parameters:

reversed - TRUE if the list should be reversed, FALSE otherwise

Support DBvolution at Patreon

Returns:

a list of all DBRows in this QueryGraph in a smart an order as possible.

toListIncludingCartesian

public List<DBRow> toListIncludingCartesian()

Return all tables in the QueryGraph as a list.

Starting from a semi-random table (see getStartTable()) traverse the graph and add all nodes found to the list.

This method scans across discontinuities. If there is a cartesian join/discontinuity present all of the nodes will be returned. Use toList() if you need to avoid spanning a discontinuity.

Some optimization is attempted, by trying to include all the required/inner tables first before adding the optional/outer tables. This avoids a common problem of a query that spans the intersection of 2 optional/outer tables, creating mid-query cartesian join that could have been avoided by including a related required/inner table first.

Support DBvolution at Patreon

Returns:

a list of all DBRows in this QueryGraph in a smart an order as possible.

toListIncludingCartesianReversable

public List<DBRow> toListIncludingCartesianReversable(Boolean reverse)

Return all tables in the QueryGraph as a list.

Starting from a semi-random table (see getStartTable()) traverse the graph and add all nodes found to the list.

This method scans across discontinuities. If there is a cartesian join/discontinuity present all of the nodes will be returned. Use toList() if you need to avoid spanning a discontinuity.

Some optimization is attempted, by trying to include all the required/inner tables first before adding the optional/outer tables. This avoids a common problem of a query that spans the intersection of 2 optional/outer tables, creating mid-query cartesian join that could have been avoided by including a related required/inner table first.

Parameters:

reverse - TRUE if the list needs to be reversed, FALSE otherwise

Support DBvolution at Patreon

Returns:

a list of all DBRows in this QueryGraph in a smart an order as possible.

getJungGraph

public edu.uci.ics.jung.graph.Graph<QueryGraphNode,DBExpression> getJungGraph()

Create a Jung graph of this QueryGraph for display purposes.

Other graphs are available but we use Graph.

Support DBvolution at Patreon

Returns:

a Jung Graph.