[td-98] optimize put performance by comparing the minimum key of skip list...

[td-98] optimize put performance by comparing the minimum key of skip list before starting to find the appropriated position in the list.

src/util/inc/tskiplist.h

@@ -50,6 +50,8 @@ typedef struct SSkipListNode {
 #define SL_GET_NODE_DATA(n) ((char *)(n) + SL_NODE_HEADER_SIZE((n)->level))
 #define SL_GET_NODE_KEY(s, n) ((s)->keyFn(SL_GET_NODE_DATA(n)))
 
+#define SL_GET_SL_MIN_KEY(s) (SL_GET_NODE_KEY((s), SL_GET_FORWARD_POINTER((s)->pHead, 0)))
+
 #define SL_GET_NODE_LEVEL(n) *(uint8_t *)((n))
 
 /*

src/util/src/tskiplist.c

@@ -71,7 +71,8 @@ memset(pNode, 0, SL_NODE_HEADER_SIZE(_l));\
 } while(0)
 
 static void tSkipListDoInsert(SSkipList *pSkipList, SSkipListNode **forward, SSkipListNode *pNode);
-static SSkipListNode* tSkipListDoAppend(SSkipList *pSkipList, SSkipListNode *pNode);
+static SSkipListNode* tSkipListPushBack(SSkipList *pSkipList, SSkipListNode *pNode);
+static SSkipListNode* tSkipListPushFront(SSkipList* pSkipList, SSkipListNode *pNode);
 static SSkipListIterator* doCreateSkipListIterator(SSkipList *pSkipList, int32_t order);
 
 static bool initForwardBackwardPtr(SSkipList* pSkipList) {
@@ -207,10 +208,17 @@ SSkipListNode *tSkipListPut(SSkipList *pSkipList, SSkipListNode *pNode) {
     pthread_rwlock_wrlock(pSkipList->lock);
   }
   
-  // the new key is greater than the last key of skiplist append it at last position
+  // if the new key is greater than the maximum key of skip list, push back this node at the end of skip list
   char *newDatakey = SL_GET_NODE_KEY(pSkipList, pNode);
   if (pSkipList->size == 0 || pSkipList->comparFn(pSkipList->lastKey, newDatakey) < 0) {
-    return tSkipListDoAppend(pSkipList, pNode);
+    return tSkipListPushBack(pSkipList, pNode);
+  }
+  
+  // if the new key is less than the minimum key of skip list, push front this node at the front of skip list
+  assert(pSkipList->size > 0);
+  char* minKey = SL_GET_SL_MIN_KEY(pSkipList);
+  if (pSkipList->comparFn(newDatakey, minKey) < 0) {
+    return tSkipListPushFront(pSkipList, pNode);
   }
   
   // find the appropriated position to insert data
@@ -269,7 +277,17 @@ void tSkipListDoInsert(SSkipList *pSkipList, SSkipListNode **forward, SSkipListN
   }
 }
 
-SSkipListNode* tSkipListDoAppend(SSkipList *pSkipList, SSkipListNode *pNode) {
+SSkipListNode* tSkipListPushFront(SSkipList* pSkipList, SSkipListNode *pNode) {
+  SSkipListNode* forward[MAX_SKIP_LIST_LEVEL] = {0};
+  for(int32_t i = 0; i < pSkipList->level; ++i) {
+    forward[i] = pSkipList->pHead;
+  }
+  
+  tSkipListDoInsert(pSkipList, forward, pNode);
+  return pNode;
+}
+
+SSkipListNode* tSkipListPushBack(SSkipList *pSkipList, SSkipListNode *pNode) {
   // do clear pointer area
   DO_MEMSET_PTR_AREA(pNode);