wehub-resource-sync
96 lines
2.9 KiB
Go
96 lines
2.9 KiB
Go
// Copyright 2025 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/dolthub/go-mysql-server/sql"
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"github.com/dolthub/go-mysql-server/sql/expression"
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pgtypes "github.com/dolthub/doltgresql/server/types"
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)
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// IsNull is an implementation of sql.Expression for the IS NULL operator and
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// includes Postgres-specific logic for handling records and composites.
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type IsNull struct {
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expression.UnaryExpressionStub
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}
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var _ sql.Expression = (*IsNull)(nil)
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var _ sql.CollationCoercible = (*IsNull)(nil)
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var _ sql.IsNullExpression = (*IsNull)(nil)
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// NewIsNull creates a new IsNull expression.
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func NewIsNull(child sql.Expression) *IsNull {
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return &IsNull{expression.UnaryExpressionStub{Child: child}}
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}
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// IsNullExpression implements the sql.IsNullExpression interface. This function exists primarily
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// to ensure the IsNullExpression interface has a unique signature.
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func (e *IsNull) IsNullExpression() bool {
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return true
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}
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// Type implements the Expression interface.
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func (e *IsNull) Type(ctx *sql.Context) sql.Type {
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return pgtypes.Bool
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}
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// CollationCoercibility implements the interface sql.CollationCoercible.
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func (*IsNull) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
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return sql.Collation_binary, 5
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}
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// IsNullable implements the Expression interface.
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func (e *IsNull) IsNullable(ctx *sql.Context) bool {
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return false
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}
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// Eval implements the Expression interface.
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func (e *IsNull) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
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v, err := e.Child.Eval(ctx, row)
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if err != nil {
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return nil, err
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}
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// Slices of typed values (e.g. Record and Composite types in Postgres) evaluate
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// to NULL if all of their entries are NULL.
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if tupleValue, ok := v.([]pgtypes.RecordValue); ok {
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for _, typedValue := range tupleValue {
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if typedValue.Value != nil {
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return false, nil
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}
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}
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return true, nil
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}
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return v == nil, nil
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}
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func (e *IsNull) String() string {
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return e.Child.String() + " IS NULL"
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}
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func (e *IsNull) DebugString(ctx *sql.Context) string {
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return sql.DebugString(ctx, e.Child) + " IS NULL"
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}
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// WithChildren implements the Expression interface.
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func (e *IsNull) 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(e, len(children), 1)
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}
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return NewIsNull(children[0]), nil
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}
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