org.h2.command.dml

Class Select

java.lang.Object

org.h2.command.Prepared

org.h2.command.dml.Query

org.h2.command.dml.Select

public class Select
extends Query

This class represents a simple SELECT statement. For each select statement, visibleColumnCount <= distinctColumnCount <= expressionCount. The expression list count could include ORDER BY and GROUP BY expressions that are not in the select list. The call sequence is init(), mapColumns() if it's a subquery, prepare().

Field Summary

Fields inherited from class org.h2.command.Prepared

create, parameters, prepareAlways, session, sqlStatement

Constructor Summary

Constructors

Constructor and Description
Select(Session session, Select parentSelect)

Method Summary

Methods

Modifier and Type	Method and Description
void	addCondition(Expression cond) Add a condition to the list of conditions.
void	addGlobalCondition(Parameter param, int columnId, int comparisonType) Add a condition to the query.
void	addTableFilter(TableFilter filter, boolean isTop) Add a table to the query.
boolean	addWindow(java.lang.String name, Window window) Adds a named window definition.
boolean	allowGlobalConditions() Check whether adding condition to the query is allowed.
void	fireBeforeSelectTriggers() Call the before triggers on all tables.
int	getColumnCount() Get the column count of this query.
Expression	getCondition()
double	getCost() Calculate the cost to execute this query.
java.util.ArrayList<Expression>	getGroupBy()
SelectGroups	getGroupDataIfCurrent(boolean window) Get the group data if there is currently a group-by active.
Expression	getHaving()
JoinBatch	getJoinBatch()
Select	getParentSelect() Returns parent select, or null.
java.lang.String	getPlanSQL() Get the SQL statement with the execution plan.
Expression	getQualify()
SortOrder	getSortOrder()
java.util.HashSet<Table>	getTables() Get all tables that are involved in this query.
java.util.ArrayList<TableFilter>	getTopFilters()
TableFilter	getTopTableFilter()
Window	getWindow(java.lang.String name) Returns a window with specified name, or null.
void	init() Initialize the query.
boolean	isAnyDistinct()
boolean	isCacheable()
boolean	isEverything(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.
boolean	isGroupQuery() Checks if this query is a group query.
boolean	isGroupWindowStage2() Checks if window stage of group window query is performed.
boolean	isQuickAggregateQuery() Check if this is an aggregate query with direct lookup, for example a query of the type SELECT COUNT(*) FROM TEST or SELECT MAX(ID) FROM TEST.
boolean	isReadOnly() Check if this command is read only.
boolean	isUnion() Check if this is a UNION query.
boolean	isWindowQuery() Checks if this query contains window functions.
void	mapColumns(ColumnResolver resolver, int level) Map the columns to the given column resolver.
void	prepare() Prepare this statement.
void	prepareJoinBatch() Prepare join batching.
ResultInterface	queryMeta() Get an empty result set containing the meta data.
protected ResultInterface	queryWithoutCache(int maxRows, ResultTarget target) Execute the query without checking the cache.
void	setDistinct() Set the distinct flag.
void	setDistinct(Expression[] distinctExpressions) Set the DISTINCT ON expressions.
void	setDistinctIfPossible() Set the distinct flag only if it is possible, may be used as a possible optimization only.
void	setEvaluatable(TableFilter tableFilter, boolean b) Change the evaluatable flag.
void	setExpressions(java.util.ArrayList<Expression> expressions)
void	setForUpdate(boolean b) Set the 'for update' flag.
void	setGroupBy(java.util.ArrayList<Expression> group)
void	setGroupQuery() Set when SELECT statement contains (non-window) aggregate functions, GROUP BY clause or HAVING clause.
void	setHaving(Expression having)
void	setQualify(Expression qualify)
void	setWildcard() Sets a wildcard expression as in "SELECT * FROM TEST".
void	setWindowQuery() Called if this query contains window functions.
void	updateAggregate(Session s, int stage) Update all aggregate function values.

Methods inherited from class org.h2.command.dml.Query

disableCache, getCostAsExpression, getExpressions, getLimit, getMaxDataModificationId, getOffset, getType, hasOrder, isFetchPercent, isNeverLazy, isQuery, isRandomAccessResult, isStandardDistinct, isTransactional, isWithTies, prepareOrder, query, query, setFetchPercent, setLimit, setNeverLazy, setOffset, setOrder, setRandomAccessResult, setSampleSize, setWithTies

Methods inherited from class org.h2.command.Prepared

checkCanceled, checkParameters, getCteCleanups, getCurrentRowNumber, getObjectId, getParameters, getPersistedObjectId, getSession, getSQL, getSQL, getSQL, needRecompile, setCommand, setCteCleanups, setCurrentRowNumber, setParameterList, setPersistedObjectId, setPrepareAlways, setRow, setSession, setSQL, toString, update

Methods inherited from class java.lang.Object

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

Constructor Detail

Select

public Select(Session session,
      Select parentSelect)

Method Detail

isUnion

public boolean isUnion()

Description copied from class: Query

Check if this is a UNION query.

Specified by:

isUnion in class Query

Returns:

true if this is a UNION query

addTableFilter

public void addTableFilter(TableFilter filter,
                  boolean isTop)

Add a table to the query.

Parameters:

filter - the table to add

isTop - if the table can be the first table in the query plan

getTopFilters

public java.util.ArrayList<TableFilter> getTopFilters()

setExpressions

public void setExpressions(java.util.ArrayList<Expression> expressions)

setWildcard

public void setWildcard()

Sets a wildcard expression as in "SELECT * FROM TEST".

setGroupQuery

public void setGroupQuery()

Set when SELECT statement contains (non-window) aggregate functions, GROUP BY clause or HAVING clause.

setWindowQuery

public void setWindowQuery()

Called if this query contains window functions.

setGroupBy

public void setGroupBy(java.util.ArrayList<Expression> group)

getGroupBy

public java.util.ArrayList<Expression> getGroupBy()

getGroupDataIfCurrent

public SelectGroups getGroupDataIfCurrent(boolean window)

Get the group data if there is currently a group-by active.

Parameters:

window - is this a window function

Returns:

the grouped data

setDistinct

public void setDistinct()

Description copied from class: Query

Set the distinct flag.

Overrides:

setDistinct in class Query

setDistinct

public void setDistinct(Expression[] distinctExpressions)

Set the DISTINCT ON expressions.

Parameters:

distinctExpressions - array of expressions

setDistinctIfPossible

public void setDistinctIfPossible()

Description copied from class: Query

Set the distinct flag only if it is possible, may be used as a possible optimization only.

Specified by:

setDistinctIfPossible in class Query

isAnyDistinct

public boolean isAnyDistinct()

Overrides:

isAnyDistinct in class Query

Returns:

whether this query is a DISTINCT or DISTINCT ON (...) query

addWindow

public boolean addWindow(java.lang.String name,
                Window window)

Adds a named window definition.

Parameters:

name - name

window - window definition

Returns:

true if a new definition was added, false if old definition was replaced

getWindow

public Window getWindow(java.lang.String name)

Returns a window with specified name, or null.

Parameters:

name - name of the window

Returns:

the window with specified name, or null

addCondition

public void addCondition(Expression cond)

Add a condition to the list of conditions.

Parameters:

cond - the condition to add

getCondition

public Expression getCondition()

queryMeta

public ResultInterface queryMeta()

Description copied from class: Prepared

Get an empty result set containing the meta data.

Specified by:

queryMeta in class Prepared

Returns:

the result set

queryWithoutCache

protected ResultInterface queryWithoutCache(int maxRows,
                                ResultTarget target)

Description copied from class: Query

Execute the query without checking the cache. If a target is specified, the results are written to it, and the method returns null. If no target is specified, a new LocalResult is created and returned.

Specified by:

queryWithoutCache in class Query

Parameters:

maxRows - the limit as specified in the JDBC method call

target - the target to write results to

Returns:

the result

init

public void init()

Description copied from class: Query

Initialize the query.

Specified by:

init in class Query

prepare

public void prepare()

Description copied from class: Prepared

Prepare this statement.

Overrides:

prepare in class Prepared

prepareJoinBatch

public void prepareJoinBatch()

Description copied from class: Query

Prepare join batching.

Specified by:

prepareJoinBatch in class Query

getJoinBatch

public JoinBatch getJoinBatch()

getCost

public double getCost()

Description copied from class: Query

Calculate the cost to execute this query.

Specified by:

getCost in class Query

Returns:

the cost

getTables

public java.util.HashSet<Table> getTables()

Description copied from class: Query

Get all tables that are involved in this query.

Specified by:

getTables in class Query

Returns:

the set of tables

fireBeforeSelectTriggers

public void fireBeforeSelectTriggers()

Description copied from class: Query

Call the before triggers on all tables.

Specified by:

fireBeforeSelectTriggers in class Query

getPlanSQL

public java.lang.String getPlanSQL()

Description copied from class: Prepared

Get the SQL statement with the execution plan.

Overrides:

getPlanSQL in class Prepared

Returns:

the execution plan

setHaving

public void setHaving(Expression having)

getHaving

public Expression getHaving()

setQualify

public void setQualify(Expression qualify)

getQualify

public Expression getQualify()

getColumnCount

public int getColumnCount()

Description copied from class: Query

Get the column count of this query.

Specified by:

getColumnCount in class Query

Returns:

the column count

getTopTableFilter

public TableFilter getTopTableFilter()

setForUpdate

public void setForUpdate(boolean b)

Description copied from class: Query

Set the 'for update' flag.

Specified by:

setForUpdate in class Query

Parameters:

b - the new setting

mapColumns

public void mapColumns(ColumnResolver resolver,
              int level)

Description copied from class: Query

Map the columns to the given column resolver.

Specified by:

mapColumns in class Query

Parameters:

resolver - the resolver

level - the subquery level (0 is the top level query, 1 is the first subquery level)

setEvaluatable

public void setEvaluatable(TableFilter tableFilter,
                  boolean b)

Description copied from class: Query

Change the evaluatable flag. This is used when building the execution plan.

Specified by:

setEvaluatable in class Query

Parameters:

tableFilter - the table filter

b - the new value

isQuickAggregateQuery

public boolean isQuickAggregateQuery()

Check if this is an aggregate query with direct lookup, for example a query of the type SELECT COUNT(*) FROM TEST or SELECT MAX(ID) FROM TEST.

Returns:

true if a direct lookup is possible

isGroupQuery

public boolean isGroupQuery()

Checks if this query is a group query.

Returns:

whether this query is a group query.

isWindowQuery

public boolean isWindowQuery()

Checks if this query contains window functions.

Returns:

whether this query contains window functions

isGroupWindowStage2

public boolean isGroupWindowStage2()

Checks if window stage of group window query is performed. If true, column resolver may not be used.

Returns:

true if window stage of group window query is performed

addGlobalCondition

public void addGlobalCondition(Parameter param,
                      int columnId,
                      int comparisonType)

Description copied from class: Query

Add a condition to the query. This is used for views.

Specified by:

addGlobalCondition in class Query

Parameters:

param - the parameter

columnId - the column index (0 meaning the first column)

comparisonType - the comparison type

updateAggregate

public void updateAggregate(Session s,
                   int stage)

Description copied from class: Query

Update all aggregate function values.

Specified by:

updateAggregate in class Query

Parameters:

s - the session

stage - select stage

isEverything

public boolean isEverything(ExpressionVisitor visitor)

Description copied from class: Query

Check if this expression and all sub-expressions can fulfill a criteria. If any part returns false, the result is false.

Specified by:

isEverything in class Query

Parameters:

visitor - the visitor

Returns:

if the criteria can be fulfilled

isReadOnly

public boolean isReadOnly()

Description copied from class: Prepared

Check if this command is read only.

Overrides:

isReadOnly in class Prepared

Returns:

true if it is

isCacheable

public boolean isCacheable()

Overrides:

isCacheable in class Prepared

allowGlobalConditions

public boolean allowGlobalConditions()

Description copied from class: Query

Check whether adding condition to the query is allowed. This is not allowed for views that have an order by and a limit, as it would affect the returned results.

Specified by:

allowGlobalConditions in class Query

Returns:

true if adding global conditions is allowed

getSortOrder

public SortOrder getSortOrder()

getParentSelect

public Select getParentSelect()

Returns parent select, or null.

Returns:

parent select, or null