Package org.h2.expression
Class Expression
java.lang.Object
org.h2.expression.Expression
- Direct Known Subclasses:
Alias
,ArrayConstructorByQuery
,Condition
,DataAnalysisOperation
,ExpressionColumn
,ExpressionList
,Function0_1
,JavaFunction
,Operation0
,Operation1
,Operation1_2
,Operation2
,OperationN
,SimpleCase
,Subquery
,Wildcard
An expression is a operation, a value, or a function in a query.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate boolean
static final int
Wrap expression in parentheses only if it can't be safely included into other expressions without them.static final int
State for expressions inside an aggregate formapColumns(ColumnResolver, int, int)
.static final int
State for expressions inside a window function formapColumns(ColumnResolver, int, int)
.static final int
Initial state formapColumns(ColumnResolver, int, int)
.static final int
Wrap expression in parentheses unconditionally.static final int
Do not wrap expression in parentheses.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 -
Method Summary
Modifier and TypeMethodDescriptionvoid
addFilterConditions
(TableFilter filter) Add conditions to a table filter if they can be evaluated.void
createIndexConditions
(SessionLocal session, TableFilter filter) Create index conditions if possible and attach them to the table filter.getAlias
(SessionLocal session, int columnIndex) Get the alias name of a column or SQL expression if it is not an aliased expression.boolean
getBooleanValue
(SessionLocal session) Get the value in form of a boolean expression.getColumnName
(SessionLocal session, int columnIndex) Get the column name or alias name of this expression.getColumnNameForView
(SessionLocal session, int columnIndex) Get the column name of this expression for a view.abstract int
getCost()
Estimate the cost to process the expression.final StringBuilder
getEnclosedSQL
(StringBuilder builder, int sqlFlags) Get the SQL statement of this expression.Returns the main expression, skipping aliases.getNotIfPossible
(SessionLocal session) If it is possible, return the negated expression.int
Check whether this expression is a column and can store NULL.Get the schema name, or nullfinal String
getSQL
(int sqlFlags) Get the SQL statement of this expression.final String
getSQL
(int sqlFlags, int parentheses) Get the SQL statement of this expression.final StringBuilder
getSQL
(StringBuilder builder, int sqlFlags) Appends the SQL statement of this object to the specified builder.final StringBuilder
getSQL
(StringBuilder builder, int sqlFlags, int parentheses) Get the SQL statement of this expression.getSubexpression
(int index) Returns subexpression with specified index.int
Returns count of subexpressions.Get the table alias name or null if this expression does not represent a column.Get the table name, or nullabstract TypeInfo
getType()
Returns the data type.abstract StringBuilder
getUnenclosedSQL
(StringBuilder builder, int sqlFlags) Get the SQL statement of this expression.abstract Value
getValue
(SessionLocal session) Return the resulting value for the current row.getWhenSQL
(StringBuilder builder, int sqlFlags) Appends the SQL statement of this when operand to the specified builder.boolean
getWhenValue
(SessionLocal session, Value left) Return the resulting value of when operand for the current row.boolean
Check if this expression will always return the same value.abstract boolean
isEverything
(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.boolean
Check if this is an identity column.boolean
Check if this expression will always return the NULL value.boolean
Is the value of a parameter set.boolean
Returns whether this expression is a right side of condition in a when operand.abstract void
mapColumns
(ColumnResolver resolver, int level, int state) Map the columns of the resolver to expression columns.boolean
Returns whether this expressions needs to be wrapped in parentheses when it is used as an argument of other expressions.abstract Expression
optimize
(SessionLocal session) Try to optimize the expression.final Expression
optimizeCondition
(SessionLocal session) Try to optimize or remove the condition.abstract void
setEvaluatable
(TableFilter tableFilter, boolean value) Tell the expression columns whether the table filter can return values now.toString()
Convert this expression to a String.abstract void
updateAggregate
(SessionLocal session, int stage) Update an aggregate value.static StringBuilder
writeExpressions
(StringBuilder builder, List<? extends Expression> expressions, int sqlFlags) Get the SQL snippet for a list of expressions.static StringBuilder
writeExpressions
(StringBuilder builder, Expression[] expressions, int sqlFlags) Get the SQL snippet for an array of expressions.Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface org.h2.util.HasSQL
getTraceSQL
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Field Details
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MAP_INITIAL
public static final int MAP_INITIALInitial state formapColumns(ColumnResolver, int, int)
.- See Also:
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MAP_IN_WINDOW
public static final int MAP_IN_WINDOWState for expressions inside a window function formapColumns(ColumnResolver, int, int)
.- See Also:
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MAP_IN_AGGREGATE
public static final int MAP_IN_AGGREGATEState for expressions inside an aggregate formapColumns(ColumnResolver, int, int)
.- See Also:
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AUTO_PARENTHESES
public static final int AUTO_PARENTHESESWrap expression in parentheses only if it can't be safely included into other expressions without them.- See Also:
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WITH_PARENTHESES
public static final int WITH_PARENTHESESWrap expression in parentheses unconditionally.- See Also:
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WITHOUT_PARENTHESES
public static final int WITHOUT_PARENTHESESDo not wrap expression in parentheses.- See Also:
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addedToFilter
private boolean addedToFilter
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Constructor Details
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Expression
public Expression()
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Method Details
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writeExpressions
public static StringBuilder writeExpressions(StringBuilder builder, List<? extends Expression> expressions, int sqlFlags) Get the SQL snippet for a list of expressions.- Parameters:
builder
- the builder to append the SQL toexpressions
- the list of expressionssqlFlags
- formatting flags- Returns:
- the specified string builder
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writeExpressions
public static StringBuilder writeExpressions(StringBuilder builder, Expression[] expressions, int sqlFlags) Get the SQL snippet for an array of expressions.- Parameters:
builder
- the builder to append the SQL toexpressions
- the list of expressionssqlFlags
- formatting flags- Returns:
- the specified string builder
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getValue
Return the resulting value for the current row.- Parameters:
session
- the session- Returns:
- the result
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getType
Returns the data type. The data type may be unknown before the optimization phase. -
mapColumns
Map the columns of the resolver to expression columns.- Parameters:
resolver
- the column resolverlevel
- the subquery nesting levelstate
- current state for nesting checks, initial value isMAP_INITIAL
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optimize
Try to optimize the expression.- Parameters:
session
- the session- Returns:
- the optimized expression
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optimizeCondition
Try to optimize or remove the condition.- Parameters:
session
- the session- Returns:
- the optimized condition, or
null
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setEvaluatable
Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.- Parameters:
tableFilter
- the table filtervalue
- true if the table filter can return value
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getSQL
Description copied from interface:HasSQL
Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization. -
getSQL
Description copied from interface:HasSQL
Appends the SQL statement of this object to the specified builder. -
getSQL
Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization.- Parameters:
sqlFlags
- formatting flagsparentheses
- parentheses mode- Returns:
- the SQL statement
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getSQL
Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization.- Parameters:
builder
- string buildersqlFlags
- formatting flagsparentheses
- parentheses mode- Returns:
- the specified string builder
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needParentheses
public boolean needParentheses()Returns whether this expressions needs to be wrapped in parentheses when it is used as an argument of other expressions.- Returns:
true
if it is
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getEnclosedSQL
Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization. Enclosing '(' and ')' are always appended.- Parameters:
builder
- string buildersqlFlags
- formatting flags- Returns:
- the specified string builder
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getUnenclosedSQL
Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization. Enclosing '(' and ')' are never appended.- Parameters:
builder
- string buildersqlFlags
- formatting flags- Returns:
- the specified string builder
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updateAggregate
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.- Parameters:
session
- the sessionstage
- select stage
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isEverything
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
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getCost
public abstract int getCost()Estimate the cost to process the expression. Used when optimizing the query, to calculate the query plan with the lowest estimated cost.- Returns:
- the estimated cost
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getNotIfPossible
If it is possible, return the negated expression. This is used to optimize NOT expressions: NOT ID>10 can be converted to ID<=10. Returns null if negating is not possible.- Parameters:
session
- the session- Returns:
- the negated expression, or null
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isConstant
public boolean isConstant()Check if this expression will always return the same value.- Returns:
- if the expression is constant
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isNullConstant
public boolean isNullConstant()Check if this expression will always return the NULL value.- Returns:
- if the expression is constant NULL value
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isValueSet
public boolean isValueSet()Is the value of a parameter set.- Returns:
- true if set
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isIdentity
public boolean isIdentity()Check if this is an identity column.- Returns:
- true if it is an identity column
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getBooleanValue
Get the value in form of a boolean expression. Returns true or false. In this database, everything can be a condition.- Parameters:
session
- the session- Returns:
- the result
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createIndexConditions
Create index conditions if possible and attach them to the table filter.- Parameters:
session
- the sessionfilter
- the table filter
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getColumnName
Get the column name or alias name of this expression.- Parameters:
session
- the sessioncolumnIndex
- 0-based column index- Returns:
- the column name
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getSchemaName
Get the schema name, or null- Returns:
- the schema name
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getTableName
Get the table name, or null- Returns:
- the table name
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getNullable
public int getNullable()Check whether this expression is a column and can store NULL.- Returns:
- whether NULL is allowed
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getTableAlias
Get the table alias name or null if this expression does not represent a column.- Returns:
- the table alias name
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getAlias
Get the alias name of a column or SQL expression if it is not an aliased expression.- Parameters:
session
- the sessioncolumnIndex
- 0-based column index- Returns:
- the alias name
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getColumnNameForView
Get the column name of this expression for a view.- Parameters:
session
- the sessioncolumnIndex
- 0-based column index- Returns:
- the column name for a view
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getNonAliasExpression
Returns the main expression, skipping aliases.- Returns:
- the expression
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addFilterConditions
Add conditions to a table filter if they can be evaluated.- Parameters:
filter
- the table filter
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toString
Convert this expression to a String. -
getSubexpressionCount
public int getSubexpressionCount()Returns count of subexpressions.- Returns:
- count of subexpressions
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getSubexpression
Returns subexpression with specified index.- Parameters:
index
- 0-based index- Returns:
- subexpression with specified index, may be null
- Throws:
IndexOutOfBoundsException
- if specified index is not valid
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getWhenValue
Return the resulting value of when operand for the current row.- Parameters:
session
- the sessionleft
- value on the left side- Returns:
- the result
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getWhenSQL
Appends the SQL statement of this when operand to the specified builder.- Parameters:
builder
- string buildersqlFlags
- formatting flags- Returns:
- the specified string builder
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isWhenConditionOperand
public boolean isWhenConditionOperand()Returns whether this expression is a right side of condition in a when operand.- Returns:
true
if it is,false
otherwise
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