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