tidb/pkg/bindinfo/session_handle.go

// Copyright 2019 PingCAP, Inc.
//
// Licensed 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 bindinfo

import (
	"context"
	"encoding/json"
	"strings"
	"time"

	"github.com/pingcap/errors"
	"github.com/pingcap/tidb/pkg/bindinfo/norm"
	"github.com/pingcap/tidb/pkg/metrics"
	"github.com/pingcap/tidb/pkg/parser"
	"github.com/pingcap/tidb/pkg/parser/ast"
	"github.com/pingcap/tidb/pkg/parser/mysql"
	"github.com/pingcap/tidb/pkg/sessionctx"
	"github.com/pingcap/tidb/pkg/sessionctx/sessionstates"
	"github.com/pingcap/tidb/pkg/types"
	"github.com/pingcap/tidb/pkg/util/hack"
	"github.com/pingcap/tidb/pkg/util/logutil"
	"go.uber.org/zap"
)

// SessionBindingHandle is used to handle all session sql bind operations.
type SessionBindingHandle interface {
	// CreateSessionBinding creates a binding to the cache.
	CreateSessionBinding(sctx sessionctx.Context, binding Binding) (err error)

	// DropSessionBinding drops a binding by the sql digest.
	DropSessionBinding(sqlDigest string) error

	// MatchSessionBinding returns the matched binding for this statement.
	MatchSessionBinding(sctx sessionctx.Context, fuzzyDigest string, tableNames []*ast.TableName) (matchedBinding Binding, isMatched bool)

	// GetAllSessionBindings return all bindings.
	GetAllSessionBindings() (bindings Bindings)

	// Close closes the SessionBindingHandle.
	Close()

	sessionctx.SessionStatesHandler
}

// sessionBindingHandle is used to handle all session sql bind operations.
type sessionBindingHandle struct {
	ch BindingCache
}

// NewSessionBindingHandle creates a new SessionBindingHandle.
func NewSessionBindingHandle() SessionBindingHandle {
	sessionHandle := &sessionBindingHandle{}
	sessionHandle.ch = newBindCache()
	return sessionHandle
}

// appendSessionBinding adds the Bindings to the cache, all the stale bindMetas are
// removed from the cache after this operation.
func (h *sessionBindingHandle) appendSessionBinding(sqlDigest string, meta Bindings) {
	oldBindings := h.ch.GetBinding(sqlDigest)
	err := h.ch.SetBinding(sqlDigest, meta)
	if err != nil {
		logutil.BgLogger().Warn("SessionHandle.appendSessionBinding", zap.String("category", "sql-bind"), zap.Error(err))
	}
	updateMetrics(metrics.ScopeSession, oldBindings, meta, false)
}

// CreateSessionBinding creates a Bindings to the cache.
// It replaces all the exists bindings for the same normalized SQL.
func (h *sessionBindingHandle) CreateSessionBinding(sctx sessionctx.Context, binding Binding) (err error) {
	if err := prepareHints(sctx, &binding); err != nil {
		return err
	}
	binding.Db = strings.ToLower(binding.Db)
	now := types.NewTime(types.FromGoTime(time.Now().In(sctx.GetSessionVars().StmtCtx.TimeZone())), mysql.TypeTimestamp, 3)
	binding.CreateTime = now
	binding.UpdateTime = now

	// update the BindMeta to the cache.
	h.appendSessionBinding(parser.DigestNormalized(binding.OriginalSQL).String(), []Binding{binding})
	return nil
}

// DropSessionBinding drop Bindings in the cache.
func (h *sessionBindingHandle) DropSessionBinding(sqlDigest string) error {
	if sqlDigest == "" {
		return errors.New("sql digest is empty")
	}
	h.ch.RemoveBinding(sqlDigest)
	return nil
}

// MatchSessionBinding returns the matched binding for this statement.
func (h *sessionBindingHandle) MatchSessionBinding(sctx sessionctx.Context, fuzzyDigest string, tableNames []*ast.TableName) (matchedBinding Binding, isMatched bool) {
	// The current implementation is simplistic, but session binding is only for test purpose, so
	// there shouldn't be many session bindings, and to keep it simple, this implementation is acceptable.
	leastWildcards := len(tableNames) + 1
	bindings := h.ch.GetAllBindings()
	enableFuzzyBinding := sctx.GetSessionVars().EnableFuzzyBinding
	for _, binding := range bindings {
		bindingStmt, err := parser.New().ParseOneStmt(binding.BindSQL, binding.Charset, binding.Collation)
		if err != nil {
			return
		}
		_, bindingFuzzyDigest := norm.NormalizeStmtForBinding(bindingStmt, norm.WithFuzz(true))
		if bindingFuzzyDigest != fuzzyDigest {
			continue
		}
		bindingTableNames := CollectTableNames(bindingStmt)

		numWildcards, matched := fuzzyMatchBindingTableName(sctx.GetSessionVars().CurrentDB, tableNames, bindingTableNames)
		if matched && numWildcards > 0 && sctx != nil && !enableFuzzyBinding {
			continue // fuzzy binding is disabled, skip this binding
		}
		if matched && numWildcards < leastWildcards {
			matchedBinding = binding
			isMatched = true
			leastWildcards = numWildcards
		}
	}
	return
}

// GetAllSessionBindings return all session bind info.
func (h *sessionBindingHandle) GetAllSessionBindings() (bindings Bindings) {
	return h.ch.GetAllBindings()
}

// EncodeSessionStates implements SessionStatesHandler.EncodeSessionStates interface.
func (h *sessionBindingHandle) EncodeSessionStates(_ context.Context, _ sessionctx.Context, sessionStates *sessionstates.SessionStates) error {
	bindings := h.ch.GetAllBindings()
	if len(bindings) == 0 {
		return nil
	}
	bytes, err := json.Marshal([]Binding(bindings))
	if err != nil {
		return err
	}
	sessionStates.Bindings = string(hack.String(bytes))
	return nil
}

// DecodeSessionStates implements SessionStatesHandler.DecodeSessionStates interface.
func (h *sessionBindingHandle) DecodeSessionStates(_ context.Context, sctx sessionctx.Context, sessionStates *sessionstates.SessionStates) error {
	if len(sessionStates.Bindings) == 0 {
		return nil
	}
	var records []Binding
	if err := json.Unmarshal(hack.Slice(sessionStates.Bindings), &records); err != nil {
		return err
	}
	for _, record := range records {
		// Restore hints and ID because hints are hard to encode.
		if err := prepareHints(sctx, &record); err != nil {
			return err
		}
		h.appendSessionBinding(parser.DigestNormalized(record.OriginalSQL).String(), []Binding{record})
	}

	return nil
}

// Close closes the session handle.
func (h *sessionBindingHandle) Close() {
	updateMetrics(metrics.ScopeSession, h.ch.GetAllBindings(), nil, false)
}

// sessionBindInfoKeyType is a dummy type to avoid naming collision in context.
type sessionBindInfoKeyType int

// String defines a Stringer function for debugging and pretty printing.
func (sessionBindInfoKeyType) String() string {
	return "session_bindinfo"
}

// SessionBindInfoKeyType is a variable key for store session bind info.
const SessionBindInfoKeyType sessionBindInfoKeyType = 0