com.hazelcast.org.apache.calcite.rel.RelDistribution Maven / Gradle / Ivy
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* the License. You may obtain a copy of the License at
*
* http://www.apache.com.hazelcast.org.licenses/LICENSE-2.0
*
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package com.hazelcast.org.apache.calcite.rel;
import com.hazelcast.org.apache.calcite.plan.RelMultipleTrait;
import com.hazelcast.org.apache.calcite.util.mapping.Mappings;
import java.util.List;
import javax.annotation.Nonnull;
/**
* Description of the physical distribution of a relational expression.
*
* TBD:
*
* - Can we shorten {@link Type#HASH_DISTRIBUTED} to HASH, etc.
* - Do we need {@link RelDistributions}.DEFAULT?
* - {@link RelDistributionTraitDef#convert}
* does not create specific physical operators as it does in Drill. Drill
* will need to create rules; or we could allow "converters" to be
* registered with the planner that are not trait-defs.
*
*/
public interface RelDistribution extends RelMultipleTrait {
/** Returns the type of distribution. */
@Nonnull Type getType();
/**
* Returns the ordinals of the key columns.
*
* Order is important for some types (RANGE); other types (HASH) consider
* it unimportant but impose an arbitrary order; other types (BROADCAST,
* SINGLETON) never have keys.
*/
@Nonnull List getKeys();
/**
* Applies mapping to this distribution trait.
*
* Mapping can change the distribution trait only if it depends on distribution keys.
*
*
For example if relation is HASH distributed by keys [0, 1], after applying
* a mapping (3, 2, 1, 0), the relation will have a distribution HASH(2,3) because
* distribution keys changed their ordinals.
*
*
If mapping eliminates one of the distribution keys, the {@link Type#ANY}
* distribution will be returned.
*
*
If distribution doesn't have keys (BROADCAST or SINGLETON), method will return
* the same distribution.
*
* @param mapping Mapping
* @return distribution with mapping applied
*/
RelDistribution apply(Mappings.TargetMapping mapping);
/** Type of distribution. */
enum Type {
/** There is only one instance of the stream. It sees all records. */
SINGLETON("single"),
/** There are multiple instances of the stream, and each instance contains
* records whose keys hash to a particular hash value. Instances are
* disjoint; a given record appears on exactly one stream. */
HASH_DISTRIBUTED("hash"),
/** There are multiple instances of the stream, and each instance contains
* records whose keys fall into a particular range. Instances are disjoint;
* a given record appears on exactly one stream. */
RANGE_DISTRIBUTED("range"),
/** There are multiple instances of the stream, and each instance contains
* randomly chosen records. Instances are disjoint; a given record appears
* on exactly one stream. */
RANDOM_DISTRIBUTED("random"),
/** There are multiple instances of the stream, and records are assigned
* to instances in turn. Instances are disjoint; a given record appears
* on exactly one stream. */
ROUND_ROBIN_DISTRIBUTED("rr"),
/** There are multiple instances of the stream, and all records appear in
* each instance. */
BROADCAST_DISTRIBUTED("broadcast"),
/** Not a valid distribution, but indicates that a consumer will accept any
* distribution. */
ANY("any");
public final String shortName;
Type(String shortName) {
this.shortName = shortName;
}
}
}