org.apache.calcite.sql.type

Class SqlTypeCoercionRule

java.lang.Object

org.apache.calcite.sql.type.SqlTypeCoercionRule

All Implemented Interfaces:

SqlTypeMappingRule

public class SqlTypeCoercionRule
extends Object
implements SqlTypeMappingRule

Rules that determine whether a type is castable from another type.

These rules specify the conversion matrix with explicit CAST.

The implicit type coercion matrix should be a sub-set of this explicit one. We do not define an implicit type coercion matrix, instead we have specific coercion rules for all kinds of SQL contexts which actually define the "matrix".

To add a new implementation to this class, follow these steps:

1. Initialize a SqlTypeMappingRules.Builder instance with default mappings of INSTANCE.
2. Modify the mappings with the Builder.
3. Construct a new SqlTypeCoercionRule instance with method instance(Map).
4. Set the SqlTypeCoercionRule instance into the SqlValidator.

The code snippet below illustrates how to implement a customized instance.

     // Initialize a Builder instance with the default mappings.
     Builder builder = SqlTypeMappingRules.builder();
     builder.addAll(SqlTypeCoercionRules.instance().getTypeMapping());

     // Do the tweak, for example, if we want to add a rule to allow
     // coerce BOOLEAN to TIMESTAMP.
     builder.add(SqlTypeName.TIMESTAMP,
         builder.copyValues(SqlTypeName.TIMESTAMP)
             .add(SqlTypeName.BOOLEAN).build());

     // Initialize a SqlTypeCoercionRules with the new builder mappings.
     SqlTypeCoercionRules typeCoercionRules = SqlTypeCoercionRules.instance(builder.map);

     // Set the SqlTypeCoercionRules instance into the SqlValidator.
     SqlValidator.Config validatorConf ...;
     validatorConf.withTypeCoercionRules(typeCoercionRules);
     // Use this conf to initialize the SqlValidator.
 

Field Summary

Fields

Modifier and Type	Field and Description
static ThreadLocal<SqlTypeCoercionRule>	THREAD_PROVIDERS

Method Summary

Modifier and Type	Method and Description
Map<SqlTypeName,com.google.common.collect.ImmutableSet<SqlTypeName>>	getTypeMapping() Returns the type mappings of this rule instance.
static SqlTypeCoercionRule	instance() Returns an instance.
static SqlTypeCoercionRule	instance(Map<SqlTypeName,com.google.common.collect.ImmutableSet<SqlTypeName>> map) Returns an instance with specified type mappings.

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.type.SqlTypeMappingRule

canApplyFrom

Field Detail

THREAD_PROVIDERS

public static final ThreadLocal<SqlTypeCoercionRule> THREAD_PROVIDERS

Method Detail

instance

public static SqlTypeCoercionRule instance()

Returns an instance.

instance

public static SqlTypeCoercionRule instance(Map<SqlTypeName,com.google.common.collect.ImmutableSet<SqlTypeName>> map)

Returns an instance with specified type mappings.

getTypeMapping

public Map<SqlTypeName,com.google.common.collect.ImmutableSet<SqlTypeName>> getTypeMapping()

Description copied from interface: SqlTypeMappingRule

Returns the type mappings of this rule instance.

The mappings should be immutable.

Specified by:

getTypeMapping in interface SqlTypeMappingRule