Class Expression

    • Constructor Detail

      • Expression

        public Expression()
    • Method Detail

      • writeExpressions

        public static java.lang.StringBuilder writeExpressions​(java.lang.StringBuilder builder,
                                                               java.util.List<? extends Expression> expressions,
                                                               int sqlFlags)
        Get the SQL snippet for a list of expressions.
        Parameters:
        builder - the builder to append the SQL to
        expressions - the list of expressions
        sqlFlags - formatting flags
        Returns:
        the specified string builder
      • writeExpressions

        public static java.lang.StringBuilder writeExpressions​(java.lang.StringBuilder builder,
                                                               Expression[] expressions,
                                                               int sqlFlags)
        Get the SQL snippet for an array of expressions.
        Parameters:
        builder - the builder to append the SQL to
        expressions - the list of expressions
        sqlFlags - formatting flags
        Returns:
        the specified string builder
      • getValue

        public abstract Value getValue​(SessionLocal session)
        Return the resulting value for the current row.
        Parameters:
        session - the session
        Returns:
        the result
      • getType

        public abstract TypeInfo getType()
        Returns the data type. The data type may be unknown before the optimization phase.
        Specified by:
        getType in interface Typed
        Returns:
        the data type
      • mapColumns

        public abstract void mapColumns​(ColumnResolver resolver,
                                        int level,
                                        int state)
        Map the columns of the resolver to expression columns.
        Parameters:
        resolver - the column resolver
        level - the subquery nesting level
        state - current state for nesting checks, initial value is MAP_INITIAL
      • optimize

        public abstract Expression optimize​(SessionLocal session)
        Try to optimize the expression.
        Parameters:
        session - the session
        Returns:
        the optimized expression
      • optimizeCondition

        public final Expression optimizeCondition​(SessionLocal session)
        Try to optimize or remove the condition.
        Parameters:
        session - the session
        Returns:
        the optimized condition, or null
      • setEvaluatable

        public abstract void setEvaluatable​(TableFilter tableFilter,
                                            boolean value)
        Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.
        Parameters:
        tableFilter - the table filter
        value - true if the table filter can return value
      • getSQL

        public final java.lang.String getSQL​(int sqlFlags)
        Description copied from interface: HasSQL
        Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization.
        Specified by:
        getSQL in interface HasSQL
        Parameters:
        sqlFlags - formatting flags
        Returns:
        the SQL statement
      • getSQL

        public final java.lang.StringBuilder getSQL​(java.lang.StringBuilder builder,
                                                    int sqlFlags)
        Description copied from interface: HasSQL
        Appends the SQL statement of this object to the specified builder.
        Specified by:
        getSQL in interface HasSQL
        Parameters:
        builder - string builder
        sqlFlags - formatting flags
        Returns:
        the specified string builder
      • getSQL

        public final java.lang.String getSQL​(int sqlFlags,
                                             int parentheses)
        Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization.
        Parameters:
        sqlFlags - formatting flags
        parentheses - parentheses mode
        Returns:
        the SQL statement
      • getSQL

        public final java.lang.StringBuilder getSQL​(java.lang.StringBuilder builder,
                                                    int sqlFlags,
                                                    int parentheses)
        Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization.
        Parameters:
        builder - string builder
        sqlFlags - formatting flags
        parentheses - parentheses mode
        Returns:
        the specified string builder
      • 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
      • getEnclosedSQL

        public final java.lang.StringBuilder getEnclosedSQL​(java.lang.StringBuilder builder,
                                                            int sqlFlags)
        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 builder
        sqlFlags - formatting flags
        Returns:
        the specified string builder
      • getUnenclosedSQL

        public abstract java.lang.StringBuilder getUnenclosedSQL​(java.lang.StringBuilder builder,
                                                                 int sqlFlags)
        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 builder
        sqlFlags - formatting flags
        Returns:
        the specified string builder
      • updateAggregate

        public abstract void updateAggregate​(SessionLocal session,
                                             int stage)
        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 session
        stage - select stage
      • 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
      • 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
      • getNotIfPossible

        public Expression getNotIfPossible​(SessionLocal session)
        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
      • isConstant

        public boolean isConstant()
        Check if this expression will always return the same value.
        Returns:
        if the expression is constant
      • isNullConstant

        public boolean isNullConstant()
        Check if this expression will always return the NULL value.
        Returns:
        if the expression is constant NULL value
      • isValueSet

        public boolean isValueSet()
        Is the value of a parameter set.
        Returns:
        true if set
      • isIdentity

        public boolean isIdentity()
        Check if this is an identity column.
        Returns:
        true if it is an identity column
      • getBooleanValue

        public boolean getBooleanValue​(SessionLocal session)
        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
      • createIndexConditions

        public void createIndexConditions​(SessionLocal session,
                                          TableFilter filter)
        Create index conditions if possible and attach them to the table filter.
        Parameters:
        session - the session
        filter - the table filter
      • getColumnName

        public java.lang.String getColumnName​(SessionLocal session,
                                              int columnIndex)
        Get the column name or alias name of this expression.
        Parameters:
        session - the session
        columnIndex - 0-based column index
        Returns:
        the column name
      • getSchemaName

        public java.lang.String getSchemaName()
        Get the schema name, or null
        Returns:
        the schema name
      • getTableName

        public java.lang.String getTableName()
        Get the table name, or null
        Returns:
        the table name
      • getNullable

        public int getNullable()
        Check whether this expression is a column and can store NULL.
        Returns:
        whether NULL is allowed
      • getTableAlias

        public java.lang.String getTableAlias()
        Get the table alias name or null if this expression does not represent a column.
        Returns:
        the table alias name
      • getAlias

        public 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.
        Parameters:
        session - the session
        columnIndex - 0-based column index
        Returns:
        the alias name
      • getColumnNameForView

        public java.lang.String getColumnNameForView​(SessionLocal session,
                                                     int columnIndex)
        Get the column name of this expression for a view.
        Parameters:
        session - the session
        columnIndex - 0-based column index
        Returns:
        the column name for a view
      • getNonAliasExpression

        public Expression getNonAliasExpression()
        Returns the main expression, skipping aliases.
        Returns:
        the expression
      • addFilterConditions

        public void addFilterConditions​(TableFilter filter)
        Add conditions to a table filter if they can be evaluated.
        Parameters:
        filter - the table filter
      • toString

        public java.lang.String toString()
        Convert this expression to a String.
        Overrides:
        toString in class java.lang.Object
        Returns:
        the string representation
      • getSubexpressionCount

        public int getSubexpressionCount()
        Returns count of subexpressions.
        Returns:
        count of subexpressions
      • getSubexpression

        public Expression getSubexpression​(int index)
        Returns subexpression with specified index.
        Parameters:
        index - 0-based index
        Returns:
        subexpression with specified index, may be null
        Throws:
        java.lang.IndexOutOfBoundsException - if specified index is not valid
      • getWhenValue

        public boolean getWhenValue​(SessionLocal session,
                                    Value left)
        Return the resulting value of when operand for the current row.
        Parameters:
        session - the session
        left - value on the left side
        Returns:
        the result
      • getWhenSQL

        public java.lang.StringBuilder getWhenSQL​(java.lang.StringBuilder builder,
                                                  int sqlFlags)
        Appends the SQL statement of this when operand to the specified builder.
        Parameters:
        builder - string builder
        sqlFlags - formatting flags
        Returns:
        the specified string builder
      • 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