public class LegacyLimitHandler extends AbstractLimitHandler
Limit handler that delegates all operations to the underlying dialect.
Constructor and Description |
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LegacyLimitHandler(Dialect dialect)
Constructs a LegacyLimitHandler
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Modifier and Type | Method and Description |
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boolean |
bindLimitParametersFirst()
Does the <tt>LIMIT</tt> clause come at the start of the
<tt>SELECT</tt> statement, rather than at the end?
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boolean |
bindLimitParametersInReverseOrder()
ANSI SQL defines the LIMIT clause to be in the form LIMIT offset, limit.
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int |
convertToFirstRowValue(int zeroBasedFirstResult)
Hibernate APIs explicitly state that setFirstResult() should be a zero-based offset.
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boolean |
forceLimitUsage()
Generally, if there is no limit applied to a Hibernate query we do not apply any limits
to the SQL query.
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String |
processSql(String sql,
RowSelection selection)
Return processed SQL query.
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boolean |
supportsLimit()
Does this handler support some form of limiting query results
via a SQL clause?
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boolean |
supportsLimitOffset()
Does this handler’s LIMIT support (if any) additionally
support specifying an offset?
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boolean |
supportsVariableLimit()
Does this handler support bind variables (i.e., prepared statement
parameters) for its limit/offset?
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boolean |
useMaxForLimit()
Does the <tt>LIMIT</tt> clause take a "maximum" row number instead
of a total number of returned rows?
<p/>
This is easiest understood via an example.
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bindLimitParameters, bindLimitParametersAtEndOfQuery, bindLimitParametersAtStartOfQuery, getMaxOrLimit, setMaxRows
public LegacyLimitHandler(Dialect dialect)
Constructs a LegacyLimitHandler
dialect
- The dialectpublic boolean supportsLimit()
LimitHandler
Does this handler support some form of limiting query results via a SQL clause?
supportsLimit
in interface LimitHandler
supportsLimit
in class AbstractLimitHandler
public boolean supportsLimitOffset()
LimitHandler
Does this handler’s LIMIT support (if any) additionally support specifying an offset?
supportsLimitOffset
in interface LimitHandler
supportsLimitOffset
in class AbstractLimitHandler
public boolean supportsVariableLimit()
AbstractLimitHandler
Does this handler support bind variables (i.e., prepared statement parameters) for its limit/offset?
supportsVariableLimit
in class AbstractLimitHandler
public boolean bindLimitParametersInReverseOrder()
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?
bindLimitParametersInReverseOrder
in class AbstractLimitHandler
public boolean bindLimitParametersFirst()
AbstractLimitHandler
Does the <tt>LIMIT</tt> clause come at the start of the <tt>SELECT</tt> statement, rather than at the end?
bindLimitParametersFirst
in class AbstractLimitHandler
public boolean useMaxForLimit()
AbstractLimitHandler
Does the <tt>LIMIT</tt> clause take a "maximum" row number instead of a total number of returned rows? <p/> 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) <p/> So essentially, is limit relative from offset? Or is limit absolute?
useMaxForLimit
in class AbstractLimitHandler
public boolean forceLimitUsage()
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.
forceLimitUsage
in class AbstractLimitHandler
public int convertToFirstRowValue(int zeroBasedFirstResult)
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.
<p/>
NOTE: what gets passed into AbstractLimitHandler.processSql(String, org.hibernate.engine.spi.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.
convertToFirstRowValue
in class AbstractLimitHandler
zeroBasedFirstResult
- The user-supplied, zero-based first row offset.Query.setFirstResult(int)
,
Criteria.setFirstResult(int)
public String processSql(String sql, RowSelection selection)
LimitHandler
Return processed SQL query.
processSql
in interface LimitHandler
processSql
in class AbstractLimitHandler
sql
- the SQL query to process.selection
- the selection criteria for rows.Copyright © 2001-2018 Red Hat, Inc. All Rights Reserved.