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Cassandra adapter for Calcite
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.calcite.adapter.cassandra;
import org.apache.calcite.adapter.enumerable.EnumerableLimit;
import org.apache.calcite.adapter.java.JavaTypeFactory;
import org.apache.calcite.plan.Convention;
import org.apache.calcite.plan.RelOptRule;
import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.plan.RelOptRuleOperand;
import org.apache.calcite.plan.RelOptUtil;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelCollation;
import org.apache.calcite.rel.RelCollations;
import org.apache.calcite.rel.RelFieldCollation;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.convert.ConverterRule;
import org.apache.calcite.rel.core.RelFactories;
import org.apache.calcite.rel.core.Sort;
import org.apache.calcite.rel.logical.LogicalFilter;
import org.apache.calcite.rel.logical.LogicalProject;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rex.RexCall;
import org.apache.calcite.rex.RexInputRef;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.rex.RexVisitorImpl;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.sql.validate.SqlValidatorUtil;
import org.apache.calcite.util.Pair;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.function.Predicate;
/**
* Rules and relational operators for
* {@link CassandraRel#CONVENTION}
* calling convention.
*/
public class CassandraRules {
private CassandraRules() {}
public static final RelOptRule[] RULES = {
CassandraFilterRule.INSTANCE,
CassandraProjectRule.INSTANCE,
CassandraSortRule.INSTANCE,
CassandraLimitRule.INSTANCE
};
static List cassandraFieldNames(final RelDataType rowType) {
return SqlValidatorUtil.uniquify(rowType.getFieldNames(),
SqlValidatorUtil.EXPR_SUGGESTER, true);
}
/** Translator from {@link RexNode} to strings in Cassandra's expression
* language. */
static class RexToCassandraTranslator extends RexVisitorImpl {
private final JavaTypeFactory typeFactory;
private final List inFields;
protected RexToCassandraTranslator(JavaTypeFactory typeFactory,
List inFields) {
super(true);
this.typeFactory = typeFactory;
this.inFields = inFields;
}
@Override public String visitInputRef(RexInputRef inputRef) {
return inFields.get(inputRef.getIndex());
}
}
/** Base class for planner rules that convert a relational expression to
* Cassandra calling convention. */
abstract static class CassandraConverterRule extends ConverterRule {
protected final Convention out;
CassandraConverterRule(Class clazz,
String description) {
this(clazz, r -> true, description);
}
CassandraConverterRule(Class clazz,
Predicate predicate,
String description) {
super(clazz, predicate, Convention.NONE,
CassandraRel.CONVENTION, RelFactories.LOGICAL_BUILDER, description);
this.out = CassandraRel.CONVENTION;
}
}
/**
* Rule to convert a {@link org.apache.calcite.rel.logical.LogicalFilter} to a
* {@link CassandraFilter}.
*/
private static class CassandraFilterRule extends RelOptRule {
private static final Predicate PREDICATE =
// TODO: Check for an equality predicate on the partition key
// Right now this just checks if we have a single top-level AND
filter -> RelOptUtil.disjunctions(filter.getCondition()).size() == 1;
private static final CassandraFilterRule INSTANCE = new CassandraFilterRule();
private CassandraFilterRule() {
super(operand(LogicalFilter.class, operand(CassandraTableScan.class, none())),
"CassandraFilterRule");
}
@Override public boolean matches(RelOptRuleCall call) {
// Get the condition from the filter operation
LogicalFilter filter = call.rel(0);
RexNode condition = filter.getCondition();
// Get field names from the scan operation
CassandraTableScan scan = call.rel(1);
Pair, List> keyFields = scan.cassandraTable.getKeyFields();
Set partitionKeys = new HashSet<>(keyFields.left);
List fieldNames = CassandraRules.cassandraFieldNames(filter.getInput().getRowType());
List disjunctions = RelOptUtil.disjunctions(condition);
if (disjunctions.size() != 1) {
return false;
} else {
// Check that all conjunctions are primary key equalities
condition = disjunctions.get(0);
for (RexNode predicate : RelOptUtil.conjunctions(condition)) {
if (!isEqualityOnKey(predicate, fieldNames, partitionKeys, keyFields.right)) {
return false;
}
}
}
// Either all of the partition keys must be specified or none
return partitionKeys.size() == keyFields.left.size() || partitionKeys.size() == 0;
}
/** Check if the node is a supported predicate (primary key equality).
*
* @param node Condition node to check
* @param fieldNames Names of all columns in the table
* @param partitionKeys Names of primary key columns
* @param clusteringKeys Names of primary key columns
* @return True if the node represents an equality predicate on a primary key
*/
private boolean isEqualityOnKey(RexNode node, List fieldNames,
Set partitionKeys, List clusteringKeys) {
if (node.getKind() != SqlKind.EQUALS) {
return false;
}
RexCall call = (RexCall) node;
final RexNode left = call.operands.get(0);
final RexNode right = call.operands.get(1);
String key = compareFieldWithLiteral(left, right, fieldNames);
if (key == null) {
key = compareFieldWithLiteral(right, left, fieldNames);
}
if (key != null) {
return partitionKeys.remove(key) || clusteringKeys.contains(key);
} else {
return false;
}
}
/** Check if an equality operation is comparing a primary key column with a literal.
*
* @param left Left operand of the equality
* @param right Right operand of the equality
* @param fieldNames Names of all columns in the table
* @return The field being compared or null if there is no key equality
*/
private String compareFieldWithLiteral(RexNode left, RexNode right, List fieldNames) {
// FIXME Ignore casts for new and assume they aren't really necessary
if (left.isA(SqlKind.CAST)) {
left = ((RexCall) left).getOperands().get(0);
}
if (left.isA(SqlKind.INPUT_REF) && right.isA(SqlKind.LITERAL)) {
final RexInputRef left1 = (RexInputRef) left;
String name = fieldNames.get(left1.getIndex());
return name;
} else {
return null;
}
}
/** @see org.apache.calcite.rel.convert.ConverterRule */
public void onMatch(RelOptRuleCall call) {
LogicalFilter filter = call.rel(0);
CassandraTableScan scan = call.rel(1);
if (filter.getTraitSet().contains(Convention.NONE)) {
final RelNode converted = convert(filter, scan);
if (converted != null) {
call.transformTo(converted);
}
}
}
public RelNode convert(LogicalFilter filter, CassandraTableScan scan) {
final RelTraitSet traitSet = filter.getTraitSet().replace(CassandraRel.CONVENTION);
final Pair, List> keyFields = scan.cassandraTable.getKeyFields();
return new CassandraFilter(
filter.getCluster(),
traitSet,
convert(filter.getInput(), CassandraRel.CONVENTION),
filter.getCondition(),
keyFields.left,
keyFields.right,
scan.cassandraTable.getClusteringOrder());
}
}
/**
* Rule to convert a {@link org.apache.calcite.rel.logical.LogicalProject}
* to a {@link CassandraProject}.
*/
private static class CassandraProjectRule extends CassandraConverterRule {
private static final CassandraProjectRule INSTANCE = new CassandraProjectRule();
private CassandraProjectRule() {
super(LogicalProject.class, "CassandraProjectRule");
}
@Override public boolean matches(RelOptRuleCall call) {
LogicalProject project = call.rel(0);
for (RexNode e : project.getProjects()) {
if (!(e instanceof RexInputRef)) {
return false;
}
}
return true;
}
public RelNode convert(RelNode rel) {
final LogicalProject project = (LogicalProject) rel;
final RelTraitSet traitSet = project.getTraitSet().replace(out);
return new CassandraProject(project.getCluster(), traitSet,
convert(project.getInput(), out), project.getProjects(),
project.getRowType());
}
}
/**
* Rule to convert a {@link org.apache.calcite.rel.core.Sort} to a
* {@link CassandraSort}.
*/
private static class CassandraSortRule extends RelOptRule {
private static final RelOptRuleOperand CASSANDRA_OP =
operand(CassandraToEnumerableConverter.class,
operandJ(CassandraFilter.class, null,
// We can only use implicit sorting within a single partition
CassandraFilter::isSinglePartition, any()));
private static final CassandraSortRule INSTANCE = new CassandraSortRule();
private CassandraSortRule() {
super(
operandJ(Sort.class, null,
// Limits are handled by CassandraLimit
sort -> sort.offset == null && sort.fetch == null, CASSANDRA_OP),
"CassandraSortRule");
}
public RelNode convert(Sort sort, CassandraFilter filter) {
final RelTraitSet traitSet =
sort.getTraitSet().replace(CassandraRel.CONVENTION)
.replace(sort.getCollation());
return new CassandraSort(sort.getCluster(), traitSet,
convert(sort.getInput(), traitSet.replace(RelCollations.EMPTY)),
sort.getCollation());
}
public boolean matches(RelOptRuleCall call) {
final Sort sort = call.rel(0);
final CassandraFilter filter = call.rel(2);
return collationsCompatible(sort.getCollation(), filter.getImplicitCollation());
}
/** Check if it is possible to exploit native CQL sorting for a given collation.
*
* @return True if it is possible to achieve this sort in Cassandra
*/
private boolean collationsCompatible(RelCollation sortCollation,
RelCollation implicitCollation) {
List sortFieldCollations = sortCollation.getFieldCollations();
List implicitFieldCollations = implicitCollation.getFieldCollations();
if (sortFieldCollations.size() > implicitFieldCollations.size()) {
return false;
}
if (sortFieldCollations.size() == 0) {
return true;
}
// Check if we need to reverse the order of the implicit collation
boolean reversed = reverseDirection(sortFieldCollations.get(0).getDirection())
== implicitFieldCollations.get(0).getDirection();
for (int i = 0; i < sortFieldCollations.size(); i++) {
RelFieldCollation sorted = sortFieldCollations.get(i);
RelFieldCollation implied = implicitFieldCollations.get(i);
// Check that the fields being sorted match
if (sorted.getFieldIndex() != implied.getFieldIndex()) {
return false;
}
// Either all fields must be sorted in the same direction
// or the opposite direction based on whether we decided
// if the sort direction should be reversed above
RelFieldCollation.Direction sortDirection = sorted.getDirection();
RelFieldCollation.Direction implicitDirection = implied.getDirection();
if ((!reversed && sortDirection != implicitDirection)
|| (reversed && reverseDirection(sortDirection) != implicitDirection)) {
return false;
}
}
return true;
}
/** Find the reverse of a given collation direction.
*
* @return Reverse of the input direction
*/
private RelFieldCollation.Direction reverseDirection(RelFieldCollation.Direction direction) {
switch (direction) {
case ASCENDING:
case STRICTLY_ASCENDING:
return RelFieldCollation.Direction.DESCENDING;
case DESCENDING:
case STRICTLY_DESCENDING:
return RelFieldCollation.Direction.ASCENDING;
default:
return null;
}
}
/** @see org.apache.calcite.rel.convert.ConverterRule */
public void onMatch(RelOptRuleCall call) {
final Sort sort = call.rel(0);
CassandraFilter filter = call.rel(2);
final RelNode converted = convert(sort, filter);
if (converted != null) {
call.transformTo(converted);
}
}
}
/**
* Rule to convert a {@link org.apache.calcite.adapter.enumerable.EnumerableLimit} to a
* {@link CassandraLimit}.
*/
private static class CassandraLimitRule extends RelOptRule {
private static final CassandraLimitRule INSTANCE = new CassandraLimitRule();
private CassandraLimitRule() {
super(operand(EnumerableLimit.class, operand(CassandraToEnumerableConverter.class, any())),
"CassandraLimitRule");
}
public RelNode convert(EnumerableLimit limit) {
final RelTraitSet traitSet =
limit.getTraitSet().replace(CassandraRel.CONVENTION);
return new CassandraLimit(limit.getCluster(), traitSet,
convert(limit.getInput(), CassandraRel.CONVENTION), limit.offset, limit.fetch);
}
/** @see org.apache.calcite.rel.convert.ConverterRule */
public void onMatch(RelOptRuleCall call) {
final EnumerableLimit limit = call.rel(0);
final RelNode converted = convert(limit);
if (converted != null) {
call.transformTo(converted);
}
}
}
}
// End CassandraRules.java