wehub-resource-sync
146 lines
4.4 KiB
Go
146 lines
4.4 KiB
Go
// Copyright 2024 Dolthub, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package expression
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import (
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"github.com/cockroachdb/errors"
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"github.com/dolthub/go-mysql-server/sql"
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"github.com/dolthub/go-mysql-server/sql/expression"
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"github.com/dolthub/doltgresql/server/functions/framework"
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)
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// JoinComparator is specifically for handling how GMS implements joins by implementing expression.Comparer over binary
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// operators.
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type JoinComparator struct {
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eq *BinaryOperator
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less *BinaryOperator
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}
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var _ sql.Expression = (*JoinComparator)(nil)
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var _ expression.BinaryExpression = (*JoinComparator)(nil)
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var _ expression.Equality = (*JoinComparator)(nil)
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var _ expression.Comparer = (*JoinComparator)(nil)
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// NewJoinComparator returns a new *JoinComparator.
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func NewJoinComparator(ctx *sql.Context, eq *BinaryOperator) (*JoinComparator, error) {
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if eq.operator != framework.Operator_BinaryEqual {
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return nil, errors.Errorf("join comparator may only be created from equality operators")
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}
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less, err := (&BinaryOperator{operator: framework.Operator_BinaryLessThan}).WithResolvedChildren(ctx, []any{eq.Left(), eq.Right()})
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if err != nil {
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return nil, err
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}
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return &JoinComparator{
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eq: eq,
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less: less.(*BinaryOperator),
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}, nil
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}
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// Children implements the sql.Expression interface.
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func (j *JoinComparator) Children() []sql.Expression {
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return []sql.Expression{j.eq}
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}
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// Compare implements the expression.Comparer interface.
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func (j *JoinComparator) Compare(ctx *sql.Context, row sql.Row) (int, error) {
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// Check equals
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res, err := j.eq.Eval(ctx, row)
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if err != nil {
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return 0, err
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}
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if res.(bool) {
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return 0, nil
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}
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// Check less than
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res, err = j.less.Eval(ctx, row)
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if err != nil {
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return 0, err
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}
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if res.(bool) {
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return -1, nil
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}
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// We'll assume it's greater
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return 1, nil
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}
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// Eval implements the sql.Expression interface.
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func (j *JoinComparator) Eval(ctx *sql.Context, row sql.Row) (any, error) {
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// We only care about less in Compare.
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return j.eq.Eval(ctx, row)
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}
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// IsNullable implements the sql.Expression interface.
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func (j *JoinComparator) IsNullable(ctx *sql.Context) bool {
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return j.eq.IsNullable(ctx)
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}
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// RepresentsEquality implements the expression.Equality interface.
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func (j *JoinComparator) RepresentsEquality() bool {
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return j.eq.RepresentsEquality()
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}
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// Resolved implements the sql.Expression interface.
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func (j *JoinComparator) Resolved() bool {
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return j.eq.Resolved() && j.less.Resolved()
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}
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// String implements the sql.Expression interface.
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func (j *JoinComparator) String() string {
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return j.eq.String()
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}
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// SwapParameters implements the expression.Equality interface.
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func (j *JoinComparator) SwapParameters(ctx *sql.Context) (expression.Equality, error) {
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newOper, err := j.eq.SwapParameters(ctx)
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if err != nil {
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return nil, err
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}
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return NewJoinComparator(ctx, newOper.(*BinaryOperator))
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}
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// ToComparer implements the expression.Equality interface.
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func (j *JoinComparator) ToComparer(ctx *sql.Context) (expression.Comparer, error) {
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return j, nil
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}
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// Type implements the sql.Expression interface.
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func (j *JoinComparator) Type(ctx *sql.Context) sql.Type {
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return j.eq.Type(ctx)
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}
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// WithChildren implements the sql.Expression interface.
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func (j *JoinComparator) WithChildren(ctx *sql.Context, children ...sql.Expression) (sql.Expression, error) {
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if len(children) != 1 {
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return nil, sql.ErrInvalidChildrenNumber.New(j, len(children), 1)
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}
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binaryOper, ok := children[0].(*BinaryOperator)
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if !ok {
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return nil, errors.Errorf("expected join comparator child to be a binary operator but has type `%T`", children[0])
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}
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return NewJoinComparator(ctx, binaryOper)
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}
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// Left implements the expression.BinaryExpression interface.
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func (j *JoinComparator) Left() sql.Expression {
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return j.eq.Left()
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}
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// Right implements the expression.BinaryExpression interface.
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func (j *JoinComparator) Right() sql.Expression {
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return j.eq.Right()
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}
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