org.apache.calcite.sql.validate.implicit

Class AbstractTypeCoercion

java.lang.Object

org.apache.calcite.sql.validate.implicit.AbstractTypeCoercion

All Implemented Interfaces:

TypeCoercion

Direct Known Subclasses:

TypeCoercionImpl

public abstract class AbstractTypeCoercion
extends Object
implements TypeCoercion

Base class for all the type coercion rules. If you want to have a custom type coercion rules, inheriting this class is not necessary, but would have some convenient tool methods.

We make tool methods: coerceOperandType(org.apache.calcite.sql.validate.SqlValidatorScope, org.apache.calcite.sql.SqlCall, int, org.apache.calcite.rel.type.RelDataType), coerceColumnType(org.apache.calcite.sql.validate.SqlValidatorScope, org.apache.calcite.sql.SqlNodeList, int, org.apache.calcite.rel.type.RelDataType), needToCast(org.apache.calcite.sql.validate.SqlValidatorScope, org.apache.calcite.sql.SqlNode, org.apache.calcite.rel.type.RelDataType), updateInferredType(org.apache.calcite.sql.SqlNode, org.apache.calcite.rel.type.RelDataType), updateInferredColumnType(org.apache.calcite.sql.validate.SqlValidatorScope, org.apache.calcite.sql.SqlNode, int, org.apache.calcite.rel.type.RelDataType) all overridable by derived classes, you can define system specific type coercion logic.

Caution that these methods may modify the SqlNode tree, you should know what the effect is when using these methods to customize your type coercion rules.

This class also defines the default implementation of the type widening strategies, see TypeCoercion doc and methods: getTightestCommonType(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType), getWiderTypeFor(java.util.List<org.apache.calcite.rel.type.RelDataType>, boolean), getWiderTypeForTwo(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType, boolean), getWiderTypeForDecimal(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType), commonTypeForBinaryComparison(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType) for the detail strategies.

Field Summary

Fields

Modifier and Type	Field and Description
protected RelDataTypeFactory	factory
protected SqlValidator	validator

Method Summary

Modifier and Type	Method and Description
protected boolean	coerceColumnType(SqlValidatorScope scope, SqlNodeList nodeList, int index, RelDataType targetType) Cast column at index index to target type.
protected boolean	coerceOperandsType(SqlValidatorScope scope, SqlCall call, RelDataType commonType) Coerce all the operands to commonType.
protected boolean	coerceOperandType(SqlValidatorScope scope, SqlCall call, int index, RelDataType targetType) Cast operand at index index to target type.
RelDataType	commonTypeForBinaryComparison(RelDataType type1, RelDataType type2) Determines common type for a comparison operator when one operand is String type and the other is not.
RelDataType	getTightestCommonType(RelDataType type1, RelDataType type2) Case1: type widening with no precision loss.
RelDataType	getWiderTypeFor(List<RelDataType> typeList, boolean stringPromotion) Similar to getWiderTypeForTwo(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType, boolean), but can handle sequence types.
RelDataType	getWiderTypeForDecimal(RelDataType type1, RelDataType type2) Finds a wider type when one or both types are decimal type.
RelDataType	getWiderTypeForTwo(RelDataType type1, RelDataType type2, boolean stringPromotion) Case2: type widening.
RelDataType	implicitCast(RelDataType in, SqlTypeFamily expected) Type coercion based on the inferred type from passed in operand and the SqlTypeFamily defined in the checkers, e.g. the FamilyOperandTypeChecker.
protected boolean	needToCast(SqlValidatorScope scope, SqlNode node, RelDataType toType) Decide if a SqlNode should be casted to target type, derived class can override this strategy.
protected void	updateInferredColumnType(SqlValidatorScope scope, SqlNode query, int columnIndex, RelDataType desiredType) Update inferred row type for a query, i.e.
protected void	updateInferredType(SqlNode node, RelDataType type) Update inferred type for a SqlNode.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.calcite.sql.validate.implicit.TypeCoercion

binaryArithmeticCoercion, binaryComparisonCoercion, builtinFunctionCoercion, caseWhenCoercion, inOperationCoercion, querySourceCoercion, rowTypeCoercion, userDefinedFunctionCoercion

Field Detail

validator

protected SqlValidator validator

factory

protected RelDataTypeFactory factory

Method Detail

coerceOperandType

protected boolean coerceOperandType(SqlValidatorScope scope,
                                    SqlCall call,
                                    int index,
                                    RelDataType targetType)

Cast operand at index index to target type. we do this base on the fact that validate happens before type coercion.

coerceOperandsType

protected boolean coerceOperandsType(SqlValidatorScope scope,
                                     SqlCall call,
                                     RelDataType commonType)

Coerce all the operands to commonType.

Parameters:

scope - Validator scope

call - the call

commonType - common type to coerce to

coerceColumnType

protected boolean coerceColumnType(SqlValidatorScope scope,
                                   SqlNodeList nodeList,
                                   int index,
                                   RelDataType targetType)

Cast column at index index to target type.

Parameters:

scope - Validator scope for the node list

nodeList - Column node list

index - Index of column

targetType - Target type to cast to

needToCast

protected boolean needToCast(SqlValidatorScope scope,
                             SqlNode node,
                             RelDataType toType)

Decide if a SqlNode should be casted to target type, derived class can override this strategy.

updateInferredType

protected void updateInferredType(SqlNode node,
                                  RelDataType type)

Update inferred type for a SqlNode.

updateInferredColumnType

protected void updateInferredColumnType(SqlValidatorScope scope,
                                        SqlNode query,
                                        int columnIndex,
                                        RelDataType desiredType)

Update inferred row type for a query, i.e. SqlCall that returns struct type or SqlSelect.

Parameters:

scope - Validator scope

query - Node to inferred type

columnIndex - Column index to update

desiredType - Desired column type

getTightestCommonType

public RelDataType getTightestCommonType(RelDataType type1,
                                         RelDataType type2)

Case1: type widening with no precision loss. Find the tightest common type of two types that might be used in binary expression.

Specified by:

getTightestCommonType in interface TypeCoercion

Returns:

tightest common type, i.e. INTEGER + DECIMAL(10, 2) returns DECIMAL(10, 2)

commonTypeForBinaryComparison

public RelDataType commonTypeForBinaryComparison(RelDataType type1,
                                                 RelDataType type2)

Determines common type for a comparison operator when one operand is String type and the other is not. For date + timestamp operands, use timestamp as common type, i.e. Timestamp(2017-01-01 00:00 ...) > Date(2018) evaluates to be false.

Specified by:

commonTypeForBinaryComparison in interface TypeCoercion

getWiderTypeForTwo

public RelDataType getWiderTypeForTwo(RelDataType type1,
                                      RelDataType type2,
                                      boolean stringPromotion)

Case2: type widening. The main difference with getTightestCommonType(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType) is that we allow some precision loss when widening decimal to fractional, or promote fractional to string type.

Specified by:

getWiderTypeForTwo in interface TypeCoercion

getWiderTypeForDecimal

public RelDataType getWiderTypeForDecimal(RelDataType type1,
                                          RelDataType type2)

Finds a wider type when one or both types are decimal type. If the wider decimal type's precision/scale exceeds system limitation, this rule will truncate the decimal type to the max precision/scale. For decimal and fractional types, returns a decimal type which has the higher precision of the two.

The default implementation depends on the max precision/scale of the type system, you can override it based on the specific system requirement in RelDataTypeSystem.

Specified by:

getWiderTypeForDecimal in interface TypeCoercion

getWiderTypeFor

public RelDataType getWiderTypeFor(List<RelDataType> typeList,
                                   boolean stringPromotion)

Similar to getWiderTypeForTwo(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType, boolean), but can handle sequence types. getWiderTypeForTwo(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType, boolean) doesn't satisfy the associative law, i.e. (a op b) op c may not equal to a op (b op c). This is only a problem for STRING type or nested STRING type in collection type like ARRAY. Excluding these types, getWiderTypeForTwo(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.rel.type.RelDataType, boolean) satisfies the associative law. For instance, (DATE, INTEGER, VARCHAR) should have VARCHAR as the wider common type.

Specified by:

getWiderTypeFor in interface TypeCoercion

implicitCast

public RelDataType implicitCast(RelDataType in,
                                SqlTypeFamily expected)

Type coercion based on the inferred type from passed in operand and the SqlTypeFamily defined in the checkers, e.g. the FamilyOperandTypeChecker.

Caution that we do not cast from NUMERIC to NUMERIC. See CalciteImplicitCasts for the details.

Parameters:

in - Inferred operand type

expected - Expected SqlTypeFamily of registered SqlFunction

Returns:

common type of implicit cast, null if we do not find any