Package org.h2.command.query

Class Query

java.lang.Object

org.h2.command.Prepared

org.h2.command.query.Query

Direct Known Subclasses:

Select, SelectUnion, TableValueConstructor

public abstract class Query
extends Prepared

Represents a SELECT statement (simple, or union).

Field Summary

Fields inherited from class org.h2.command.Prepared

create, parameters, prepareAlways, session, sqlStatement, sqlTokens

Method Summary

Modifier and Type	Method	Description
abstract void	addGlobalCondition(Parameter param, int columnId, int comparisonType)	Add a condition to the query.
abstract boolean	allowGlobalConditions()	Check whether adding condition to the query is allowed.
void	collectDependencies(java.util.HashSet<DbObject> dependencies)	Find and collect all DbObjects, this Prepared depends on.
void	disableCache()	Disable caching of result sets.
boolean	exists()	Execute the EXISTS predicate over the query.
abstract void	fireBeforeSelectTriggers()	Call the before triggers on all tables.
int	getColumnCount()	Get the column count of this query.
abstract double	getCost()	Calculate the cost to execute this query.
int	getCostAsExpression()	Calculate the cost when used as a subquery.
java.util.ArrayList<Expression>	getExpressions()	The list of select expressions.
Expression	getFetch()
ForUpdate	getForUpdate()	Returns FOR UPDATE clause, if any.
Expression	getIfSingleRow()	If this query is determined as a single-row query, returns a replacement expression.
long	getMaxDataModificationId()
Expression	getOffset()
QueryScope	getOuterQueryScope()	Returns the scope of the outer query.
TypeInfo	getRowDataType()	Returns data type of rows.
abstract java.util.HashSet<Table>	getTables()	Get all tables that are involved in this query.
int	getType()	Get the command type as defined in CommandInterface
boolean	hasOrder()	Whether the query has an order.
abstract void	init()	Initialize the query.
void	invalidateCachedResult(Table reason)
boolean	isAnyDistinct()
boolean	isConstantQuery()	Check if this query will always return the same value and has no side effects.
abstract boolean	isEverything(ExpressionVisitor visitor)	Check if this expression and all sub-expressions can fulfill a criteria.
boolean	isFetchPercent()
boolean	isInPredicateResult()	Returns whether result is generated for the IN predicate.
boolean	isNeverLazy()
boolean	isQuery()	Check if this object is a query.
boolean	isReadOnly()	Check if this command is read only.
boolean	isRetryable()	Returns is this command can be repeated on locking failure.
boolean	isStandardDistinct()
boolean	isTransactional()	Check if this command is transactional.
abstract boolean	isUnion()	Check if this is a UNION query.
boolean	isWithTies()
abstract void	mapColumns(ColumnResolver resolver, int level, boolean outer)	Map the columns to the given column resolver.
void	prepare()	Prepare this statement.
abstract void	prepareExpressions()
abstract void	preparePlan()
ResultInterface	query(long maxrows)	Execute the query.
ResultInterface	query(long limit, ResultTarget target)	Execute the query, writing the result to the target result.
ResultInterface	queryMeta()	Get an empty result set containing the metadata.
protected abstract ResultInterface	queryWithoutCache(long limit, ResultTarget target)	Execute the query without checking the cache.
void	setDistinctIfPossible()	Set the distinct flag only if it is possible, may be used as a possible optimization only.
abstract void	setEvaluatable(TableFilter tableFilter, boolean b)	Change the evaluatable flag.
void	setFetch(Expression fetch)
void	setFetchPercent(boolean fetchPercent)
abstract void	setForUpdate(ForUpdate forUpdate)	Set the FOR UPDATE clause.
void	setInPredicateResult()	Convert results to compatible with IN predicate.
void	setInPredicateResultSortTypes(int[] inPredicateSortTypes)	Sets sort types for the IN predicate.
void	setNeverLazy(boolean b)
void	setOffset(Expression offset)
void	setOrder(java.util.ArrayList<QueryOrderBy> order)	Set the order by list.
void	setOuterQueryScope(QueryScope outerQueryScope)	Sets the scope of the outer query.
void	setWithClause(java.util.LinkedHashMap<java.lang.String,Table> withClause)	Sets the WITH clause of this query.
void	setWithTies(boolean withTies)
Table	toTable(java.lang.String alias, Column[] columnTemplates, java.util.ArrayList<Parameter> parameters, boolean forCreateView, Query topQuery)	Converts this query to a table or a view.
abstract void	updateAggregate(SessionLocal s, int stage)	Update all aggregate function values.
protected void	writeWithList(java.lang.StringBuilder builder, int sqlFlags)

Methods inherited from class org.h2.command.Prepared

checkCanceled, checkParameters, getCurrentRowNumber, getDatabase, getObjectId, getParameters, getPersistedObjectId, getPlanSQL, getPlanSQL, getSession, getSimpleSQL, getSQL, getSQLTokens, isCacheable, isWithParamValues, needRecompile, setCommand, setCurrentRowNumber, setParameterList, setPersistedObjectId, setPrepareAlways, setRow, setSession, setSQL, setWithParamValues, toString, update

Methods inherited from class java.lang.Object

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

Method Detail

setNeverLazy

public void setNeverLazy(boolean b)

isNeverLazy

public boolean isNeverLazy()

isUnion

public abstract boolean isUnion()

Check if this is a UNION query.

Returns:

true if this is a UNION query

queryMeta

public ResultInterface queryMeta()

Description copied from class: Prepared

Get an empty result set containing the metadata.

Specified by:

queryMeta in class Prepared

Returns:

the result set

queryWithoutCache

protected abstract ResultInterface queryWithoutCache(long limit,
                                                     ResultTarget target)

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.

Parameters:

limit - the limit as specified in the JDBC method call

target - the target to write results to

Returns:

the result

init

public abstract void init()

Initialize the query.

prepare

public final void prepare()

Description copied from class: Prepared

Prepare this statement.

Overrides:

prepare in class Prepared

prepareExpressions

public abstract void prepareExpressions()

preparePlan

public abstract void preparePlan()

getExpressions

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

The list of select expressions. This may include invisible expressions such as order by expressions.

Returns:

the list of expressions

getCost

public abstract double getCost()

Calculate the cost to execute this query.

Returns:

the cost

getCostAsExpression

public int getCostAsExpression()

Calculate the cost when used as a subquery. This method returns a value between 10 and 1000000, to ensure adding other values can't result in an integer overflow.

Returns:

the estimated cost as an integer

getTables

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

Get all tables that are involved in this query.

Returns:

the set of tables

setOrder

public void setOrder(java.util.ArrayList<QueryOrderBy> order)

Set the order by list.

Parameters:

order - the order by list

hasOrder

public boolean hasOrder()

Whether the query has an order.

Returns:

true if it has

getForUpdate

public ForUpdate getForUpdate()

Returns FOR UPDATE clause, if any.

Returns:

FOR UPDATE clause or null

setForUpdate

public abstract void setForUpdate(ForUpdate forUpdate)

Set the FOR UPDATE clause.

Parameters:

forUpdate - the new FOR UPDATE clause

getColumnCount

public int getColumnCount()

Get the column count of this query.

Returns:

the column count

getRowDataType

public TypeInfo getRowDataType()

Returns data type of rows.

Returns:

data type of rows

mapColumns

public abstract void mapColumns(ColumnResolver resolver,
                                int level,
                                boolean outer)

Map the columns to the given column resolver.

Parameters:

resolver - the resolver

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

outer - whether this method was called from the outer query

setEvaluatable

public abstract void setEvaluatable(TableFilter tableFilter,
                                    boolean b)

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

Parameters:

tableFilter - the table filter

b - the new value

addGlobalCondition

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

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

Parameters:

param - the parameter

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

comparisonType - the comparison type

allowGlobalConditions

public abstract boolean allowGlobalConditions()

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.

Returns:

true if adding global conditions is allowed

isEverything

public abstract boolean isEverything(ExpressionVisitor visitor)

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

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

updateAggregate

public abstract void updateAggregate(SessionLocal s,
                                     int stage)

Update all aggregate function values.

Parameters:

s - the session

stage - select stage

fireBeforeSelectTriggers

public abstract void fireBeforeSelectTriggers()

Call the before triggers on all tables.

setDistinctIfPossible

public void setDistinctIfPossible()

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

isStandardDistinct

public boolean isStandardDistinct()

Returns:

whether this query is a plain DISTINCT query

isAnyDistinct

public boolean isAnyDistinct()

Returns:

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

isInPredicateResult

public boolean isInPredicateResult()

Returns whether result is generated for the IN predicate.

Returns:

whether result is generated for the IN predicate

setInPredicateResult

public void setInPredicateResult()

Convert results to compatible with IN predicate.

setInPredicateResultSortTypes

public void setInPredicateResultSortTypes(int[] inPredicateSortTypes)

Sets sort types for the IN predicate.

Parameters:

inPredicateSortTypes - sort types for the IN predicate

isQuery

public boolean isQuery()

Description copied from class: Prepared

Check if this object is a query.

Overrides:

isQuery in class Prepared

Returns:

true if it is

isTransactional

public boolean isTransactional()

Description copied from class: Prepared

Check if this command is transactional. If it is not, then it forces the current transaction to commit.

Specified by:

isTransactional in class Prepared

Returns:

true if it is

disableCache

public void disableCache()

Disable caching of result sets.

query

public final ResultInterface query(long maxrows)

Description copied from class: Prepared

Execute the query.

Overrides:

query in class Prepared

Parameters:

maxrows - the maximum number of rows to return

Returns:

the result set

query

public final ResultInterface query(long limit,
                                   ResultTarget target)

Execute the query, writing the result to the target result.

Parameters:

limit - the maximum number of rows to return

target - the target result (null will return the result)

Returns:

the result set (if the target is not set).

exists

public final boolean exists()

Execute the EXISTS predicate over the query.

Returns:

EXISTS predicate result

getType

public int getType()

Description copied from class: Prepared

Get the command type as defined in CommandInterface

Specified by:

getType in class Prepared

Returns:

the statement type

setOffset

public void setOffset(Expression offset)

getOffset

public Expression getOffset()

setFetch

public void setFetch(Expression fetch)

getFetch

public Expression getFetch()

setFetchPercent

public void setFetchPercent(boolean fetchPercent)

isFetchPercent

public boolean isFetchPercent()

setWithTies

public void setWithTies(boolean withTies)

isWithTies

public boolean isWithTies()

getMaxDataModificationId

public final long getMaxDataModificationId()

getOuterQueryScope

public QueryScope getOuterQueryScope()

Returns the scope of the outer query.

Returns:

the scope of the outer query

setOuterQueryScope

public void setOuterQueryScope(QueryScope outerQueryScope)

Sets the scope of the outer query.

Parameters:

outerQueryScope - the scope of the outer query

setWithClause

public void setWithClause(java.util.LinkedHashMap<java.lang.String,Table> withClause)

Sets the WITH clause of this query.

Parameters:

withClause - the WITH clause of this query

writeWithList

protected void writeWithList(java.lang.StringBuilder builder,
                             int sqlFlags)

toTable

public Table toTable(java.lang.String alias,
                     Column[] columnTemplates,
                     java.util.ArrayList<Parameter> parameters,
                     boolean forCreateView,
                     Query topQuery)

Converts this query to a table or a view.

Parameters:

alias - alias name for the view

columnTemplates - column templates, or null

parameters - the parameters

forCreateView - if true, a system session will be used for the view

topQuery - the top level query

Returns:

the table or the view

collectDependencies

public void collectDependencies(java.util.HashSet<DbObject> dependencies)

Description copied from class: Prepared

Find and collect all DbObjects, this Prepared depends on.

Overrides:

collectDependencies in class Prepared

Parameters:

dependencies - collection of dependencies to populate

isConstantQuery

public boolean isConstantQuery()

Check if this query will always return the same value and has no side effects.

Returns:

if this query will always return the same value and has no side effects.

getIfSingleRow

public Expression getIfSingleRow()

If this query is determined as a single-row query, returns a replacement expression.

Returns:

the expression, or null

isRetryable

public boolean isRetryable()

Description copied from class: Prepared

Returns is this command can be repeated on locking failure.

Overrides:

isRetryable in class Prepared

Returns:

is this command can be repeated on locking failure

invalidateCachedResult

public void invalidateCachedResult(Table reason)

Overrides:

invalidateCachedResult in class Prepared