| /* |
| * 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.drill.exec.store.http.filter; |
| |
| /** |
| * Fixed set of Drill relational operators, using well-defined |
| * names. Distilled from the more general string function names |
| * used in the query plan tree. |
| */ |
| public enum RelOp { |
| // Order of LT, LE, GE, GT is important for |
| // value comparisons |
| EQ, NE, LT, LE, GE, GT, IS_NULL, IS_NOT_NULL; |
| |
| /** |
| * Return the result of flipping the sides of an |
| * expression:</br> |
| * {@code a op b} → {@code b op.invert() a} |
| * |
| * @return a new relop resulting from flipping the sides |
| * of the expression, or this relop if the operation |
| * is symmetric. |
| */ |
| public RelOp invert() { |
| switch(this) { |
| case LT: |
| return GT; |
| case LE: |
| return GE; |
| case GT: |
| return LT; |
| case GE: |
| return LE; |
| default: |
| return this; |
| } |
| } |
| |
| /** |
| * Returns the number of arguments for the relop. |
| * @return 1 for IS (NOT) NULL, 2 otherwise |
| */ |
| public int argCount() { |
| switch (this) { |
| case IS_NULL: |
| case IS_NOT_NULL: |
| return 1; |
| default: |
| return 2; |
| } |
| } |
| |
| /** |
| * Poor-man's guess at selectivity of each operator. |
| * Should match Calcite's built-in defaults. The Calcite estimates |
| * are not great, but we need to match them. |
| * <p> |
| * If a query has access to metadata, then each predicates should |
| * have a computed selectivity based on that metadata. This |
| * mechanism should be extended to include that selectivity as a field, |
| * and pass it back from this method. |
| * |
| * @return crude estimate of operator selectivity |
| * @see {@code package org.apache.calcite.rel.metadata.RelMdUtil} |
| */ |
| public double selectivity() { |
| switch (this) { |
| case EQ: |
| return 0.15; |
| case GE: |
| case GT: |
| case LE: |
| case LT: |
| case NE: // Very bad estimate! |
| return 0.5; |
| case IS_NOT_NULL: |
| case IS_NULL: |
| return 0.9; |
| default: |
| return 0.25; |
| } |
| } |
| } |