org.hibernate.dialect.pagination

Class LegacyLimitHandler

java.lang.Object

org.hibernate.dialect.pagination.AbstractLimitHandler

org.hibernate.dialect.pagination.LegacyLimitHandler

All Implemented Interfaces:

LimitHandler

public class LegacyLimitHandler
extends AbstractLimitHandler

Limit handler that delegates all operations to the underlying dialect.

Field Summary

Fields inherited from class org.hibernate.dialect.pagination.AbstractLimitHandler

selection, sql

Constructor Summary

Constructors

Constructor and Description
LegacyLimitHandler(Dialect dialect, String sql, RowSelection selection) Constructs a LegacyLimitHandler

Method Summary

Methods

Modifier and Type	Method and Description
boolean	bindLimitParametersFirst() Does the LIMIT clause come at the start of the SELECT statement, rather than at the end?
boolean	bindLimitParametersInReverseOrder() ANSI SQL defines the LIMIT clause to be in the form LIMIT offset, limit.
int	convertToFirstRowValue(int zeroBasedFirstResult) Hibernate APIs explicitly state that setFirstResult() should be a zero-based offset.
boolean	forceLimitUsage() Generally, if there is no limit applied to a Hibernate query we do not apply any limits to the SQL query.
String	getProcessedSql() Return processed SQL query.
boolean	supportsLimit() Does this handler support some form of limiting query results via a SQL clause?
boolean	supportsLimitOffset() Does this handler's LIMIT support (if any) additionally support specifying an offset?
boolean	supportsVariableLimit() Does this handler support bind variables (i.e., prepared statement parameters) for its limit/offset?
boolean	useMaxForLimit() Does the LIMIT clause take a "maximum" row number instead of a total number of returned rows? This is easiest understood via an example.

Methods inherited from class org.hibernate.dialect.pagination.AbstractLimitHandler

bindLimitParameters, bindLimitParametersAtEndOfQuery, bindLimitParametersAtStartOfQuery, getMaxOrLimit, setMaxRows

Methods inherited from class java.lang.Object

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

Constructor Detail

LegacyLimitHandler

public LegacyLimitHandler(Dialect dialect,
                  String sql,
                  RowSelection selection)

Constructs a LegacyLimitHandler

Parameters:

dialect - The dialect

sql - The sql

selection - The row selection

Method Detail

supportsLimit

public boolean supportsLimit()

Description copied from interface: LimitHandler

Does this handler support some form of limiting query results via a SQL clause?

Specified by:

supportsLimit in interface LimitHandler

Overrides:

supportsLimit in class AbstractLimitHandler

Returns:

True if this handler supports some form of LIMIT.

supportsLimitOffset

public boolean supportsLimitOffset()

Description copied from interface: LimitHandler

Does this handler's LIMIT support (if any) additionally support specifying an offset?

Specified by:

supportsLimitOffset in interface LimitHandler

Overrides:

supportsLimitOffset in class AbstractLimitHandler

Returns:

True if the handler supports an offset within the limit support.

supportsVariableLimit

public boolean supportsVariableLimit()

Description copied from class: AbstractLimitHandler

Does this handler support bind variables (i.e., prepared statement parameters) for its limit/offset?

Overrides:

supportsVariableLimit in class AbstractLimitHandler

Returns:

True if bind variables can be used; false otherwise.

bindLimitParametersInReverseOrder

public boolean bindLimitParametersInReverseOrder()

Description copied from class: AbstractLimitHandler

ANSI SQL defines the LIMIT clause to be in the form LIMIT offset, limit. Does this dialect require us to bind the parameters in reverse order?

Overrides:

bindLimitParametersInReverseOrder in class AbstractLimitHandler

Returns:

true if the correct order is limit, offset

bindLimitParametersFirst

public boolean bindLimitParametersFirst()

Description copied from class: AbstractLimitHandler

Does the LIMIT clause come at the start of the SELECT statement, rather than at the end?

Overrides:

bindLimitParametersFirst in class AbstractLimitHandler

Returns:

true if limit parameters should come before other parameters

useMaxForLimit

public boolean useMaxForLimit()

Description copied from class: AbstractLimitHandler

Does the LIMIT clause take a "maximum" row number instead of a total number of returned rows?

This is easiest understood via an example. Consider you have a table with 20 rows, but you only want to retrieve rows number 11 through 20. Generally, a limit with offset would say that the offset = 11 and the limit = 10 (we only want 10 rows at a time); this is specifying the total number of returned rows. Some dialects require that we instead specify offset = 11 and limit = 20, where 20 is the "last" row we want relative to offset (i.e. total number of rows = 20 - 11 = 9)

So essentially, is limit relative from offset? Or is limit absolute?

Overrides:

useMaxForLimit in class AbstractLimitHandler

Returns:

True if limit is relative from offset; false otherwise.

forceLimitUsage

public boolean forceLimitUsage()

Description copied from class: AbstractLimitHandler

Generally, if there is no limit applied to a Hibernate query we do not apply any limits to the SQL query. This option forces that the limit be written to the SQL query.

Overrides:

forceLimitUsage in class AbstractLimitHandler

Returns:

True to force limit into SQL query even if none specified in Hibernate query; false otherwise.

convertToFirstRowValue

public int convertToFirstRowValue(int zeroBasedFirstResult)

Description copied from class: AbstractLimitHandler

Hibernate APIs explicitly state that setFirstResult() should be a zero-based offset. Here we allow the Dialect a chance to convert that value based on what the underlying db or driver will expect.

NOTE: what gets passed into AbstractLimitHandler.AbstractLimitHandler(String, RowSelection) is the zero-based offset. Dialects which do not AbstractLimitHandler.supportsVariableLimit() should take care to perform any needed first-row-conversion calls prior to injecting the limit values into the SQL string.

Overrides:

convertToFirstRowValue in class AbstractLimitHandler

Parameters:

zeroBasedFirstResult - The user-supplied, zero-based first row offset.

Returns:

The corresponding db/dialect specific offset.

See Also:

Query.setFirstResult(int), Criteria.setFirstResult(int)

getProcessedSql

public String getProcessedSql()

Description copied from interface: LimitHandler

Return processed SQL query.

Specified by:

getProcessedSql in interface LimitHandler

Overrides:

getProcessedSql in class AbstractLimitHandler

Returns:

Query statement with LIMIT clause applied.