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add hints
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@foreyes
foreyes committed Sep 8, 2019
1 parent 096b4bd commit 3431942
Showing 1 changed file with 134 additions and 0 deletions.
134 changes: 134 additions & 0 deletions session/session.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1045,6 +1045,128 @@ func (s *session) Execute(ctx context.Context, sql string) (recordSets []sqlexec
return
}

type sessionVarsRevertInfo struct {
varName string
datum types.Datum
}

func getHintDatumFromBool(flag bool) types.Datum {
if flag {
return types.NewStringDatum("on")
}
return types.NewStringDatum("off")
}

func (s *session) setSessionVarsByHints(stmtNode ast.StmtNode) (revertInfos []sessionVarsRevertInfo, warns []error) {
var hints []*ast.TableOptimizerHint
switch x := stmtNode.(type) {
case *ast.SelectStmt:
hints = x.TableHints
case *ast.UpdateStmt:
hints = x.TableHints
case *ast.DeleteStmt:
hints = x.TableHints
// TODO: support hint for InsertStmt
default:
return
}
var memoryQuotaHintList, noIndexMergeHintList, useToJAHintList, readReplicaHintList []*ast.TableOptimizerHint
for _, hint := range hints {
switch hint.HintName.L {
case "memory_quota":
memoryQuotaHintList = append(memoryQuotaHintList, hint)
case "no_index_merge":
noIndexMergeHintList = append(noIndexMergeHintList, hint)
case "use_toja":
useToJAHintList = append(useToJAHintList, hint)
case "read_consistent_replica":
readReplicaHintList = append(readReplicaHintList, hint)
}
}
// Handle MEMORY_QUOTA
if len(memoryQuotaHintList) > 1 {
warn := errors.New("There are multiple MEMORY_QUOTA hints, only the last one will take effect")
warns = append(warns, warn)
}
if len(memoryQuotaHintList) != 0 {
hint := memoryQuotaHintList[len(memoryQuotaHintList)-1]
// Executor use MemoryQuota < 0 to indicate no memory limit, here use it to handle hint syntax error.
if hint.MemoryQuota < 0 {
warn := errors.New("There are some syntax error in MEMORY_QUOTA hint, correct usage: MEMORY_QUOTA(10 M) or MEMORY_QUOTA(10 G)")
warns = append(warns, warn)
} else {
revertInfos = append(revertInfos, sessionVarsRevertInfo{
varName: variable.TIDBMemQuotaQuery,
datum: types.NewIntDatum(s.sessionVars.MemQuotaQuery),
})
err := variable.SetSessionSystemVar(s.sessionVars, variable.TIDBMemQuotaQuery, types.NewIntDatum(int64(hint.MemoryQuota)))
if err != nil {
// SQL hints should not trigger error.
warns = append(warns, err)
}
}
}
// Handle USE_TOJA
if len(useToJAHintList) > 1 {
warn := errors.New("There are multiple USE_TOJA hints, only the last one will take effect")
warns = append(warns, warn)
}
if len(useToJAHintList) != 0 {
revertInfos = append(revertInfos, sessionVarsRevertInfo{
varName: variable.TiDBOptInSubqToJoinAndAgg,
datum: getHintDatumFromBool(s.sessionVars.AllowInSubqToJoinAndAgg),
})
hint := useToJAHintList[len(useToJAHintList)-1]
err := variable.SetSessionSystemVar(s.sessionVars, variable.TiDBOptInSubqToJoinAndAgg, getHintDatumFromBool(hint.HintFlag))
if err != nil {
// SQL hints should not trigger error.
warns = append(warns, err)
}
}
// Handle NO_INDEX_MERGE
if len(noIndexMergeHintList) > 1 {
warn := errors.New("There are multiple NO_INDEX_MERGE hints, only the last one will take effect")
warns = append(warns, warn)
}
if len(noIndexMergeHintList) != 0 {
revertInfos = append(revertInfos, sessionVarsRevertInfo{
varName: variable.TiDBEnableIndexMerge,
datum: getHintDatumFromBool(s.sessionVars.EnableIndexMerge),
})
err := variable.SetSessionSystemVar(s.sessionVars, variable.TiDBEnableIndexMerge, getHintDatumFromBool(false))
if err != nil {
// SQL hints should not trigger error.
warns = append(warns, err)
}
}
// Handle READ_CONSISTENT_REPLICA
if len(readReplicaHintList) > 1 {
warn := errors.New("There are multiple READ_CONSISTENT_REPLICA hints, only the last one will take effect")
warns = append(warns, warn)
}
if len(readReplicaHintList) != 0 {
var datum types.Datum
switch s.sessionVars.ReplicaRead {
case kv.ReplicaReadLeader:
datum := types.NewStringDatum("leader")
case kv.ReplicaReadFollower:
datum := types.NewStringDatum("follower")
default:
// Read from learner not implement yet
}
revertInfos = append(revertInfos, sessionVarsRevertInfo{
varName: variable.TiDBReplicaRead,
datum: datum,
})
err := variable.SetSessionSystemVar(s.sessionVars, variable.TiDBReplicaRead, types.NewStringDatum("follower"))
if err != nil {
// SQL hints should not trigger error.
warns = append(warns, err)
}
}
return
}

func (s *session) execute(ctx context.Context, sql string) (recordSets []sqlexec.RecordSet, err error) {
s.PrepareTxnCtx(ctx)
connID := s.sessionVars.ConnectionID
Expand Down Expand Up @@ -1080,13 +1202,17 @@ func (s *session) execute(ctx context.Context, sql string) (recordSets []sqlexec
multiQuery := len(stmtNodes) > 1
for idx, stmtNode := range stmtNodes {
s.PrepareTxnCtx(ctx)
revertInfos, hintWarns := s.setSessionVarsByHints(stmtNode)

// Step2: Transform abstract syntax tree to a physical plan(stored in executor.ExecStmt).
startTS = time.Now()
// Some executions are done in compile stage, so we reset them before compile.
if err := executor.ResetContextOfStmt(s, stmtNode); err != nil {
return nil, err
}
for _, warn := range hintWarns {
s.sessionVars.StmtCtx.AppendWarning(warn)
}
stmt, err := compiler.Compile(ctx, stmtNode)
if err != nil {
if tempStmtNodes == nil {
Expand Down Expand Up @@ -1119,6 +1245,14 @@ func (s *session) execute(ctx context.Context, sql string) (recordSets []sqlexec
if recordSets, err = s.executeStatement(ctx, connID, stmtNode, stmt, recordSets, multiQuery); err != nil {
return nil, err
}

for _, revertInfo := range revertInfos {
err := variable.SetSessionSystemVar(s.sessionVars, revertInfo.varName, revertInfo.datum)
if err != nil {
// SQL hints should not trigger error.
s.sessionVars.StmtCtx.AppendWarning(err)
}
}
}

if s.sessionVars.ClientCapability&mysql.ClientMultiResults == 0 && len(recordSets) > 1 {
Expand Down

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