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201 lines
6.4 KiB
201 lines
6.4 KiB
// Copyright 2017 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 distsql
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import (
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"context"
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"unsafe"
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"github.com/opentracing/opentracing-go"
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"github.com/pingcap/errors"
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"github.com/pingcap/tidb/kv"
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"github.com/pingcap/tidb/metrics"
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"github.com/pingcap/tidb/sessionctx"
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"github.com/pingcap/tidb/statistics"
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"github.com/pingcap/tidb/types"
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"github.com/pingcap/tidb/util/memory"
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"github.com/pingcap/tipb/go-tipb"
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)
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// Select sends a DAG request, returns SelectResult.
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// In kvReq, KeyRanges is required, Concurrency/KeepOrder/Desc/IsolationLevel/Priority are optional.
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func Select(ctx context.Context, sctx sessionctx.Context, kvReq *kv.Request, fieldTypes []*types.FieldType, fb *statistics.QueryFeedback) (SelectResult, error) {
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if span := opentracing.SpanFromContext(ctx); span != nil && span.Tracer() != nil {
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span1 := span.Tracer().StartSpan("distsql.Select", opentracing.ChildOf(span.Context()))
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defer span1.Finish()
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ctx = opentracing.ContextWithSpan(ctx, span1)
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}
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// For testing purpose.
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if hook := ctx.Value("CheckSelectRequestHook"); hook != nil {
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hook.(func(*kv.Request))(kvReq)
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}
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if !sctx.GetSessionVars().EnableStreaming {
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kvReq.Streaming = false
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}
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enabledRateLimitAction := sctx.GetSessionVars().EnabledRateLimitAction
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resp := sctx.GetClient().Send(ctx, kvReq, sctx.GetSessionVars().KVVars, sctx.GetSessionVars().StmtCtx.MemTracker, enabledRateLimitAction)
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if resp == nil {
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err := errors.New("client returns nil response")
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return nil, err
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}
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label := metrics.LblGeneral
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if sctx.GetSessionVars().InRestrictedSQL {
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label = metrics.LblInternal
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}
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// kvReq.MemTracker is used to trace and control memory usage in DistSQL layer;
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// for streamResult, since it is a pipeline which has no buffer, it's not necessary to trace it;
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// for selectResult, we just use the kvReq.MemTracker prepared for co-processor
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// instead of creating a new one for simplification.
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if kvReq.Streaming {
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return &streamResult{
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label: "dag-stream",
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sqlType: label,
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resp: resp,
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rowLen: len(fieldTypes),
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fieldTypes: fieldTypes,
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ctx: sctx,
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feedback: fb,
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}, nil
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}
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encodetype := tipb.EncodeType_TypeDefault
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if canUseChunkRPC(sctx) {
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encodetype = tipb.EncodeType_TypeChunk
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}
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return &selectResult{
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label: "dag",
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resp: resp,
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rowLen: len(fieldTypes),
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fieldTypes: fieldTypes,
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ctx: sctx,
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feedback: fb,
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sqlType: label,
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memTracker: kvReq.MemTracker,
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encodeType: encodetype,
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}, nil
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}
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// SelectWithRuntimeStats sends a DAG request, returns SelectResult.
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// The difference from Select is that SelectWithRuntimeStats will set copPlanIDs into selectResult,
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// which can help selectResult to collect runtime stats.
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func SelectWithRuntimeStats(ctx context.Context, sctx sessionctx.Context, kvReq *kv.Request,
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fieldTypes []*types.FieldType, fb *statistics.QueryFeedback, copPlanIDs []int, rootPlanID int) (SelectResult, error) {
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sr, err := Select(ctx, sctx, kvReq, fieldTypes, fb)
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if err == nil {
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if selectResult, ok := sr.(*selectResult); ok {
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selectResult.copPlanIDs = copPlanIDs
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selectResult.rootPlanID = rootPlanID
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}
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}
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return sr, err
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}
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// Analyze do a analyze request.
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func Analyze(ctx context.Context, client kv.Client, kvReq *kv.Request, vars *kv.Variables,
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isRestrict bool, sessionMemTracker *memory.Tracker) (SelectResult, error) {
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resp := client.Send(ctx, kvReq, vars, sessionMemTracker, false)
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if resp == nil {
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return nil, errors.New("client returns nil response")
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}
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label := metrics.LblGeneral
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if isRestrict {
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label = metrics.LblInternal
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}
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result := &selectResult{
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label: "analyze",
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resp: resp,
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feedback: statistics.NewQueryFeedback(0, nil, 0, false),
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sqlType: label,
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encodeType: tipb.EncodeType_TypeDefault,
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}
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return result, nil
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}
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// Checksum sends a checksum request.
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func Checksum(ctx context.Context, client kv.Client, kvReq *kv.Request, vars *kv.Variables) (SelectResult, error) {
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// FIXME: As BR have dependency of `Checksum` and TiDB also introduced BR as dependency, Currently we can't edit
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// Checksum function signature. The two-way dependence should be removed in future.
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resp := client.Send(ctx, kvReq, vars, nil, false)
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if resp == nil {
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return nil, errors.New("client returns nil response")
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}
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result := &selectResult{
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label: "checksum",
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resp: resp,
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feedback: statistics.NewQueryFeedback(0, nil, 0, false),
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sqlType: metrics.LblGeneral,
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encodeType: tipb.EncodeType_TypeDefault,
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}
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return result, nil
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}
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// SetEncodeType sets the encoding method for the DAGRequest. The supported encoding
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// methods are:
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// 1. TypeChunk: the result is encoded using the Chunk format, refer util/chunk/chunk.go
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// 2. TypeDefault: the result is encoded row by row
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func SetEncodeType(ctx sessionctx.Context, dagReq *tipb.DAGRequest) {
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if canUseChunkRPC(ctx) {
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dagReq.EncodeType = tipb.EncodeType_TypeChunk
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setChunkMemoryLayout(dagReq)
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} else {
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dagReq.EncodeType = tipb.EncodeType_TypeDefault
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}
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}
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func canUseChunkRPC(ctx sessionctx.Context) bool {
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if !ctx.GetSessionVars().EnableChunkRPC {
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return false
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}
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if ctx.GetSessionVars().EnableStreaming {
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return false
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}
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if !checkAlignment() {
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return false
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}
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return true
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}
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var supportedAlignment = unsafe.Sizeof(types.MyDecimal{}) == 40
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// checkAlignment checks the alignment in current system environment.
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// The alignment is influenced by system, machine and Golang version.
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// Using this function can guarantee the alignment is we want.
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func checkAlignment() bool {
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return supportedAlignment
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}
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var systemEndian tipb.Endian
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// setChunkMemoryLayout sets the chunk memory layout for the DAGRequest.
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func setChunkMemoryLayout(dagReq *tipb.DAGRequest) {
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dagReq.ChunkMemoryLayout = &tipb.ChunkMemoryLayout{Endian: GetSystemEndian()}
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}
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// GetSystemEndian gets the system endian.
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func GetSystemEndian() tipb.Endian {
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return systemEndian
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}
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func init() {
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var i int = 0x0100
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ptr := unsafe.Pointer(&i)
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if 0x01 == *(*byte)(ptr) {
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systemEndian = tipb.Endian_BigEndian
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} else {
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systemEndian = tipb.Endian_LittleEndian
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}
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}
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