Package org.h2.expression.condition

Class Comparison

java.lang.Object
org.h2.expression.Expression
org.h2.expression.condition.Condition
org.h2.expression.condition.Comparison
All Implemented Interfaces:
HasSQL, Typed
public final class Comparison extends Condition
Example comparison expressions are ID=1, NAME=NAME, NAME IS NULL.

  • Field Details

    • EQUAL

      public static final int EQUAL
      The comparison type meaning = as in ID=1.
      See Also:

    • NOT_EQUAL

      public static final int NOT_EQUAL
      The comparison type meaning <> as in ID<>1.
      See Also:

    • SMALLER

      public static final int SMALLER
      The comparison type meaning < as in ID<1.
      See Also:

    • BIGGER

      public static final int BIGGER
      The comparison type meaning > as in ID>1.
      See Also:

    • SMALLER_EQUAL

      public static final int SMALLER_EQUAL
      The comparison type meaning <= as in ID<=1.
      See Also:

    • BIGGER_EQUAL

      public static final int BIGGER_EQUAL
      The comparison type meaning >= as in ID>=1.
      See Also:

    • EQUAL_NULL_SAFE

      public static final int EQUAL_NULL_SAFE
      The comparison type meaning ID IS NOT DISTINCT FROM 1.
      See Also:

    • NOT_EQUAL_NULL_SAFE

      public static final int NOT_EQUAL_NULL_SAFE
      The comparison type meaning ID IS DISTINCT FROM 1.
      See Also:

    • SPATIAL_INTERSECTS

      public static final int SPATIAL_INTERSECTS
      This is a comparison type that is only used for spatial index conditions (operator "&&").
      See Also:

    • COMPARE_TYPES

      static final String[] COMPARE_TYPES

    • FALSE

      public static final int FALSE
      This is a pseudo comparison type that is only used for index conditions. It means the comparison will always yield FALSE. Example: 1=0.
      See Also:

    • IN_LIST

      public static final int IN_LIST
      This is a pseudo comparison type that is only used for index conditions. It means equals any value of a list. Example: IN(1, 2, 3).
      See Also:

    • IN_QUERY

      public static final int IN_QUERY
      This is a pseudo comparison type that is only used for index conditions. It means equals any value of a list. Example: IN(SELECT ...).
      See Also:

    • compareType

      private int compareType

    • left

      private Expression left

    • whenOperand

      private final boolean whenOperand

  • Constructor Details

    • Comparison

      public Comparison(int compareType, Expression left, Expression right, boolean whenOperand)

  • Method Details

    • needParentheses

      public boolean needParentheses()
      Description copied from class: Expression
      Returns whether this expressions needs to be wrapped in parentheses when it is used as an argument of other expressions.
      Overrides:
      needParentheses in class Expression
      Returns:
      true if it is

    • getUnenclosedSQL

      public StringBuilder getUnenclosedSQL(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 class Expression
      Parameters:
      builder - string builder
      sqlFlags - formatting flags
      Returns:
      the specified string builder

    • getWhenSQL

      public StringBuilder getWhenSQL(StringBuilder builder, int sqlFlags)
      Description copied from class: Expression
      Appends the SQL statement of this when operand to the specified builder.
      Overrides:
      getWhenSQL in class Expression
      Parameters:
      builder - string builder
      sqlFlags - formatting flags
      Returns:
      the specified string builder

    • optimize

      public Expression optimize(SessionLocal session)
      Description copied from class: Expression
      Try to optimize the expression.
      Specified by:
      optimize in class Expression
      Parameters:
      session - the session
      Returns:
      the optimized expression

    • getValue

      public Value getValue(SessionLocal session)
      Description copied from class: Expression
      Return the resulting value for the current row.
      Specified by:
      getValue in class Expression
      Parameters:
      session - the session
      Returns:
      the result

    • getWhenValue

      public boolean getWhenValue(SessionLocal session, Value left)
      Description copied from class: Expression
      Return the resulting value of when operand for the current row.
      Overrides:
      getWhenValue in class Expression
      Parameters:
      session - the session
      left - value on the left side
      Returns:
      the result

    • compare

      static Value compare(SessionLocal session, Value l, Value r, int compareType)
      Compare two values.
      Parameters:
      session - the session
      l - the first value
      r - the second value
      compareType - the compare type
      Returns:
      result of comparison, either TRUE, FALSE, or NULL

    • isWhenConditionOperand

      public boolean isWhenConditionOperand()
      Description copied from class: Expression
      Returns whether this expression is a right side of condition in a when operand.
      Overrides:
      isWhenConditionOperand in class Expression
      Returns:
      true if it is, false otherwise

    • getReversedCompareType

      private static int getReversedCompareType(int type)

    • getNotIfPossible

      public Expression getNotIfPossible(SessionLocal session)
      Description copied from class: Expression
      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.
      Overrides:
      getNotIfPossible in class Expression
      Parameters:
      session - the session
      Returns:
      the negated expression, or null

    • getNotCompareType

      private int getNotCompareType()

    • createIndexConditions

      public void createIndexConditions(SessionLocal session, TableFilter filter)
      Description copied from class: Expression
      Create index conditions if possible and attach them to the table filter.
      Overrides:
      createIndexConditions in class Expression
      Parameters:
      session - the session
      filter - the table filter

    • createIndexConditions

      static void createIndexConditions(TableFilter filter, Expression left, Expression right, int compareType)

    • 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 class Expression
      Parameters:
      tableFilter - the table filter
      b - true if the table filter can return value

    • 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 class Expression
      Parameters:
      session - the session
      stage - select stage

    • 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 class Expression
      Parameters:
      resolver - the column resolver
      level - the subquery nesting level
      state - current state for nesting checks, initial value is Expression.MAP_INITIAL

    • 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 class Expression
      Parameters:
      visitor - the visitor
      Returns:
      if the criteria can be fulfilled

    • 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 class Expression
      Returns:
      the estimated cost

    • getIfEquals

      Expression getIfEquals(Expression match)
      Get the other expression if this is an equals comparison and the other expression matches.
      Parameters:
      match - the expression that should match
      Returns:
      null if no match, the other expression if there is a match

    • getAdditionalAnd

      Expression getAdditionalAnd(SessionLocal session, Comparison other)
      Get an additional condition if possible. Example: given two conditions A=B AND B=C, the new condition A=C is returned.
      Parameters:
      session - the session
      other - the second condition
      Returns:
      null or the third condition for indexes

    • optimizeOr

      Expression optimizeOr(SessionLocal session, Comparison other)
      Replace the OR condition with IN condition if possible. Example: given the two conditions A=1 OR A=2, the new condition A IN(1, 2) is returned.
      Parameters:
      session - the session
      other - the second condition
      Returns:
      null or the joined IN condition

    • getConditionIn

      private static ConditionIn getConditionIn(Expression left, Expression value1, Expression value2)

    • getSubexpressionCount

      public int getSubexpressionCount()
      Description copied from class: Expression
      Returns count of subexpressions.
      Overrides:
      getSubexpressionCount in class Expression
      Returns:
      count of subexpressions

    • getSubexpression

      public Expression getSubexpression(int index)
      Description copied from class: Expression
      Returns subexpression with specified index.
      Overrides:
      getSubexpression in class Expression
      Parameters:
      index - 0-based index
      Returns:
      subexpression with specified index, may be null