Package org.h2.expression
Class Alias
- java.lang.Object
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- org.h2.expression.Expression
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- org.h2.expression.Alias
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public final class Alias extends Expression
A column alias as in SELECT 'Hello' AS NAME ...
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Field Summary
Fields Modifier and Type Field Description private java.lang.String
alias
private boolean
aliasColumnName
private Expression
expr
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Fields inherited from class org.h2.expression.Expression
AUTO_PARENTHESES, MAP_IN_AGGREGATE, MAP_IN_WINDOW, MAP_INITIAL, WITH_PARENTHESES, WITHOUT_PARENTHESES
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Fields inherited from interface org.h2.util.HasSQL
ADD_PLAN_INFORMATION, DEFAULT_SQL_FLAGS, NO_CASTS, QUOTE_ONLY_WHEN_REQUIRED, REPLACE_LOBS_FOR_TRACE, TRACE_SQL_FLAGS
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Constructor Summary
Constructors Constructor Description Alias(Expression expression, java.lang.String alias, boolean aliasColumnName)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.String
getAlias(SessionLocal session, int columnIndex)
Get the alias name of a column or SQL expression if it is not an aliased expression.java.lang.String
getColumnName(SessionLocal session, int columnIndex)
Get the column name or alias name of this expression.java.lang.String
getColumnNameForView(SessionLocal session, int columnIndex)
Get the column name of this expression for a view.int
getCost()
Estimate the cost to process the expression.Expression
getNonAliasExpression()
Returns the main expression, skipping aliases.int
getNullable()
Check whether this expression is a column and can store NULL.java.lang.String
getSchemaName()
Get the schema name, or nulljava.lang.String
getTableName()
Get the table name, or nullTypeInfo
getType()
Returns the data type.java.lang.StringBuilder
getUnenclosedSQL(java.lang.StringBuilder builder, int sqlFlags)
Get the SQL statement of this expression.Value
getValue(SessionLocal session)
Return the resulting value for the current row.boolean
isEverything(ExpressionVisitor visitor)
Check if this expression and all sub-expressions can fulfill a criteria.boolean
isIdentity()
Check if this is an identity column.void
mapColumns(ColumnResolver resolver, int level, int state)
Map the columns of the resolver to expression columns.Expression
optimize(SessionLocal session)
Try to optimize the expression.void
setEvaluatable(TableFilter tableFilter, boolean b)
Tell the expression columns whether the table filter can return values now.void
updateAggregate(SessionLocal session, int stage)
Update an aggregate value.-
Methods inherited from class org.h2.expression.Expression
addFilterConditions, createIndexConditions, getBooleanValue, getEnclosedSQL, getNotIfPossible, getSQL, getSQL, getSQL, getSQL, getSubexpression, getSubexpressionCount, getTableAlias, getWhenSQL, getWhenValue, isConstant, isNullConstant, isValueSet, isWhenConditionOperand, needParentheses, optimizeCondition, toString, writeExpressions, writeExpressions
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface org.h2.util.HasSQL
getTraceSQL
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Field Detail
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alias
private final java.lang.String alias
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expr
private Expression expr
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aliasColumnName
private final boolean aliasColumnName
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Constructor Detail
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Alias
public Alias(Expression expression, java.lang.String alias, boolean aliasColumnName)
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Method Detail
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getNonAliasExpression
public Expression getNonAliasExpression()
Description copied from class:Expression
Returns the main expression, skipping aliases.- Overrides:
getNonAliasExpression
in classExpression
- Returns:
- the expression
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getValue
public Value getValue(SessionLocal session)
Description copied from class:Expression
Return the resulting value for the current row.- Specified by:
getValue
in classExpression
- Parameters:
session
- the session- Returns:
- the result
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getType
public TypeInfo getType()
Description copied from class:Expression
Returns the data type. The data type may be unknown before the optimization phase.- Specified by:
getType
in interfaceTyped
- Specified by:
getType
in classExpression
- Returns:
- the data type
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mapColumns
public void mapColumns(ColumnResolver resolver, int level, int state)
Description copied from class:Expression
Map the columns of the resolver to expression columns.- Specified by:
mapColumns
in classExpression
- Parameters:
resolver
- the column resolverlevel
- the subquery nesting levelstate
- current state for nesting checks, initial value isExpression.MAP_INITIAL
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optimize
public Expression optimize(SessionLocal session)
Description copied from class:Expression
Try to optimize the expression.- Specified by:
optimize
in classExpression
- Parameters:
session
- the session- Returns:
- the optimized expression
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setEvaluatable
public void setEvaluatable(TableFilter tableFilter, boolean b)
Description copied from class:Expression
Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.- Specified by:
setEvaluatable
in classExpression
- Parameters:
tableFilter
- the table filterb
- true if the table filter can return value
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isIdentity
public boolean isIdentity()
Description copied from class:Expression
Check if this is an identity column.- Overrides:
isIdentity
in classExpression
- Returns:
- true if it is an identity column
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getUnenclosedSQL
public java.lang.StringBuilder getUnenclosedSQL(java.lang.StringBuilder builder, int sqlFlags)
Description copied from class:Expression
Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization. Enclosing '(' and ')' are never appended.- Specified by:
getUnenclosedSQL
in classExpression
- Parameters:
builder
- string buildersqlFlags
- formatting flags- Returns:
- the specified string builder
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updateAggregate
public void updateAggregate(SessionLocal session, int stage)
Description copied from class:Expression
Update an aggregate value. This method is called at statement execution time. It is usually called once for each row, but if the expression is used multiple times (for example in the column list, and as part of the HAVING expression) it is called multiple times - the row counter needs to be used to make sure the internal state is only updated once.- Specified by:
updateAggregate
in classExpression
- Parameters:
session
- the sessionstage
- select stage
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getAlias
public java.lang.String getAlias(SessionLocal session, int columnIndex)
Description copied from class:Expression
Get the alias name of a column or SQL expression if it is not an aliased expression.- Overrides:
getAlias
in classExpression
- Parameters:
session
- the sessioncolumnIndex
- 0-based column index- Returns:
- the alias name
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getColumnNameForView
public java.lang.String getColumnNameForView(SessionLocal session, int columnIndex)
Description copied from class:Expression
Get the column name of this expression for a view.- Overrides:
getColumnNameForView
in classExpression
- Parameters:
session
- the sessioncolumnIndex
- 0-based column index- Returns:
- the column name for a view
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getNullable
public int getNullable()
Description copied from class:Expression
Check whether this expression is a column and can store NULL.- Overrides:
getNullable
in classExpression
- Returns:
- whether NULL is allowed
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isEverything
public boolean isEverything(ExpressionVisitor visitor)
Description copied from class:Expression
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 classExpression
- Parameters:
visitor
- the visitor- Returns:
- if the criteria can be fulfilled
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getCost
public int getCost()
Description copied from class:Expression
Estimate the cost to process the expression. Used when optimizing the query, to calculate the query plan with the lowest estimated cost.- Specified by:
getCost
in classExpression
- Returns:
- the estimated cost
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getSchemaName
public java.lang.String getSchemaName()
Description copied from class:Expression
Get the schema name, or null- Overrides:
getSchemaName
in classExpression
- Returns:
- the schema name
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getTableName
public java.lang.String getTableName()
Description copied from class:Expression
Get the table name, or null- Overrides:
getTableName
in classExpression
- Returns:
- the table name
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getColumnName
public java.lang.String getColumnName(SessionLocal session, int columnIndex)
Description copied from class:Expression
Get the column name or alias name of this expression.- Overrides:
getColumnName
in classExpression
- Parameters:
session
- the sessioncolumnIndex
- 0-based column index- Returns:
- the column name
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