119 lines
3.3 KiB
Go
119 lines
3.3 KiB
Go
// Copyright 2014 The ql Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSES/QL-LICENSE file.
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// Copyright 2015 PingCAP, 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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// See the License for the specific language governing permissions and
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// limitations under the License.
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package plans
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import (
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"github.com/juju/errors"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/expression"
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"github.com/pingcap/tidb/field"
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"github.com/pingcap/tidb/plan"
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"github.com/pingcap/tidb/sessionctx/variable"
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"github.com/pingcap/tidb/util/format"
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)
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var (
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_ plan.Plan = (*LimitDefaultPlan)(nil)
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_ plan.Plan = (*OffsetDefaultPlan)(nil)
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)
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// LimitDefaultPlan handles queries like SELECT .. FROM ... LIMIT N, returns at
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// most N results.
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type LimitDefaultPlan struct {
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Count uint64
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cursor uint64
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Src plan.Plan
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Fields []*field.ResultField
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}
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// Explain implements plan.Plan Explain interface.
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func (r *LimitDefaultPlan) Explain(w format.Formatter) {
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r.Src.Explain(w)
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w.Format("┌Limit %d records\n└Output field names %v\n", r.Count, r.Fields)
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}
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// Filter implements plan.Plan Filter interface.
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func (r *LimitDefaultPlan) Filter(ctx context.Context, expr expression.Expression) (plan.Plan, bool, error) {
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return r, false, nil
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}
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// GetFields implements plan.Plan GetFields interface.
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func (r *LimitDefaultPlan) GetFields() []*field.ResultField {
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return r.Fields
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}
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// Next implements plan.Plan Next interface.
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func (r *LimitDefaultPlan) Next(ctx context.Context) (row *plan.Row, err error) {
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if r.cursor == r.Count {
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return
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}
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r.cursor++
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// TODO: This is a temp solution for pass wordpress
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variable.GetSessionVars(ctx).AddFoundRows(1)
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row, err = r.Src.Next(ctx)
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return
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}
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// Close implements plan.Plan Close interface.
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func (r *LimitDefaultPlan) Close() error {
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r.cursor = 0
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return r.Src.Close()
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}
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// OffsetDefaultPlan handles SELECT ... FROM ... OFFSET N, skips N records.
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type OffsetDefaultPlan struct {
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Count uint64
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cursor uint64
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Src plan.Plan
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Fields []*field.ResultField
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}
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// Explain implements plan.Plan Explain interface.
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func (r *OffsetDefaultPlan) Explain(w format.Formatter) {
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r.Src.Explain(w)
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w.Format("┌Skip first %d records\n└Output field names %v\n", r.Count, field.RFQNames(r.Fields))
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}
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// Filter implements plan.Plan Filter interface.
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func (r *OffsetDefaultPlan) Filter(ctx context.Context, expr expression.Expression) (plan.Plan, bool, error) {
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return r, false, nil
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}
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// GetFields implements plan.Plan GetFields interface.
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func (r *OffsetDefaultPlan) GetFields() []*field.ResultField {
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return r.Fields
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}
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// Next implements plan.Plan Next interface.
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func (r *OffsetDefaultPlan) Next(ctx context.Context) (row *plan.Row, err error) {
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for r.cursor < r.Count {
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_, err = r.Src.Next(ctx)
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if err != nil {
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return nil, errors.Trace(err)
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}
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r.cursor++
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}
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return r.Src.Next(ctx)
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}
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// Close implements plan.Plan Close interface.
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func (r *OffsetDefaultPlan) Close() error {
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r.cursor = 0
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return r.Src.Close()
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}
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