From 98002db46651485e62c839b458cb0f8281869043 Mon Sep 17 00:00:00 2001
From: foreyes <foreyes_1002@163.com>
Date: Wed, 18 Sep 2019 11:27:41 +0800
Subject: [PATCH 1/2] improve code

---
 executor/executor.go | 44 ++++++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

diff --git a/executor/executor.go b/executor/executor.go
index 992d2dae7a20e..4a6bf0c7e4b44 100644
--- a/executor/executor.go
+++ b/executor/executor.go
@@ -1385,52 +1385,56 @@ func extractStmtHintsFromStmtNode(stmtNode ast.StmtNode) []*ast.TableOptimizerHi
 }
 
 func handleStmtHints(hints []*ast.TableOptimizerHint) (stmtHints stmtctx.StmtHints, warns []error) {
-	var memoryQuotaHintList, noIndexMergeHintList, useToJAHintList, readReplicaHintList []*ast.TableOptimizerHint
+	if hints == nil {
+		return
+	}
+	var memoryQuotaHint, useToJAHint *ast.TableOptimizerHint
+	var memoryQuotaHintCnt, useToJAHintCnt, noIndexMergeHintCnt, readReplicaHintCnt int
 	for _, hint := range hints {
 		switch hint.HintName.L {
 		case "memory_quota":
-			memoryQuotaHintList = append(memoryQuotaHintList, hint)
-		case "no_index_merge":
-			noIndexMergeHintList = append(noIndexMergeHintList, hint)
+			memoryQuotaHint = hint
+			memoryQuotaHintCnt++
 		case "use_toja":
-			useToJAHintList = append(useToJAHintList, hint)
+			useToJAHint = hint
+			useToJAHintCnt++
+		case "no_index_merge":
+			noIndexMergeHintCnt++
 		case "read_consistent_replica":
-			readReplicaHintList = append(readReplicaHintList, hint)
+			readReplicaHintCnt++
 		}
 	}
 	// Handle MEMORY_QUOTA
-	if len(memoryQuotaHintList) != 0 {
-		if len(memoryQuotaHintList) > 1 {
+	if memoryQuotaHintCnt != 0 {
+		if memoryQuotaHintCnt > 1 {
 			warn := errors.New("There are multiple MEMORY_QUOTA hints, only the last one will take effect")
 			warns = append(warns, warn)
 		}
-		hint := memoryQuotaHintList[len(memoryQuotaHintList)-1]
 		// Executor use MemoryQuota <= 0 to indicate no memory limit, here use < 0 to handle hint syntax error.
-		if hint.MemoryQuota < 0 {
+		if memoryQuotaHint.MemoryQuota < 0 {
 			warn := errors.New("The use of MEMORY_QUOTA hint is invalid, valid usage: MEMORY_QUOTA(10 MB) or MEMORY_QUOTA(10 GB)")
 			warns = append(warns, warn)
 		} else {
 			stmtHints.HasMemQuotaHint = true
-			stmtHints.MemQuotaQuery = hint.MemoryQuota
-			if hint.MemoryQuota == 0 {
+			stmtHints.MemQuotaQuery = memoryQuotaHint.MemoryQuota
+			if memoryQuotaHint.MemoryQuota == 0 {
 				warn := errors.New("Setting the MEMORY_QUOTA to 0 means no memory limit")
 				warns = append(warns, warn)
 			}
 		}
 	}
 	// Handle USE_TOJA
-	if len(useToJAHintList) != 0 {
-		if len(useToJAHintList) > 1 {
+	if useToJAHintCnt != 0 {
+		if useToJAHintCnt > 1 {
 			warn := errors.New("There are multiple USE_TOJA hints, only the last one will take effect")
 			warns = append(warns, warn)
 		}
-		hint := useToJAHintList[len(useToJAHintList)-1]
 		stmtHints.HasAllowInSubqToJoinAndAggHint = true
-		stmtHints.AllowInSubqToJoinAndAgg = hint.HintFlag
+		stmtHints.AllowInSubqToJoinAndAgg = useToJAHint.HintFlag
 	}
 	// Handle NO_INDEX_MERGE
-	if len(noIndexMergeHintList) != 0 {
-		if len(noIndexMergeHintList) > 1 {
+	if noIndexMergeHintCnt != 0 {
+		if noIndexMergeHintCnt > 1 {
 			warn := errors.New("There are multiple NO_INDEX_MERGE hints, only the last one will take effect")
 			warns = append(warns, warn)
 		}
@@ -1438,8 +1442,8 @@ func handleStmtHints(hints []*ast.TableOptimizerHint) (stmtHints stmtctx.StmtHin
 		stmtHints.EnableIndexMerge = false
 	}
 	// Handle READ_CONSISTENT_REPLICA
-	if len(readReplicaHintList) != 0 {
-		if len(readReplicaHintList) > 1 {
+	if readReplicaHintCnt != 0 {
+		if readReplicaHintCnt > 1 {
 			warn := errors.New("There are multiple READ_CONSISTENT_REPLICA hints, only the last one will take effect")
 			warns = append(warns, warn)
 		}

From a27600a4f824b8155533a0def8af1d6d79e2113b Mon Sep 17 00:00:00 2001
From: foreyes <foreyes_1002@163.com>
Date: Wed, 18 Sep 2019 22:22:43 +0800
Subject: [PATCH 2/2] improve code

---
 executor/executor.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/executor/executor.go b/executor/executor.go
index 4a6bf0c7e4b44..7aa3037300f6a 100644
--- a/executor/executor.go
+++ b/executor/executor.go
@@ -1385,7 +1385,7 @@ func extractStmtHintsFromStmtNode(stmtNode ast.StmtNode) []*ast.TableOptimizerHi
 }
 
 func handleStmtHints(hints []*ast.TableOptimizerHint) (stmtHints stmtctx.StmtHints, warns []error) {
-	if hints == nil {
+	if len(hints) == 0 {
 		return
 	}
 	var memoryQuotaHint, useToJAHint *ast.TableOptimizerHint