add iterator for skiplist

src/util/inc/sskiplist.h

-/*
- * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
- *
- * This program is free software: you can use, redistribute, and/or modify
- * it under the terms of the GNU Affero General Public License, version 3
- * or later ("AGPL"), as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-#if 0
-
-#ifndef TBASE_TSKIPLIST_H
-#define TBASE_TSKIPLIST_H
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#define MAX_SKIP_LIST_LEVEL 20
-
-#include <pthread.h>
-#include <stdint.h>
-#include <stdlib.h>
-
-#include "os.h"
-#include "taosdef.h"
-
-/*
- * key of each node
- * todo move to as the global structure in all search codes...
- */
-
-const static size_t SKIP_LIST_STR_KEY_LENGTH_THRESHOLD = 15;
-typedef tVariant    tSkipListKey;
-
-typedef enum tSkipListPointQueryType {
-  INCLUDE_POINT_QUERY,
-  EXCLUDE_POINT_QUERY,
-} tSkipListPointQueryType;
-
-typedef struct tSkipListNode {
-  uint16_t nLevel;
-  char *   pData;
-
-  struct tSkipListNode **pForward;
-  struct tSkipListNode **pBackward;
-
-  tSkipListKey key;
-} tSkipListNode;
-
-/*
- * @version 0.2
- * @date   2017/11/12
- * the simple version of SkipList.
- * for multi-thread safe purpose, we employ pthread_rwlock_t to guarantee to generate
- * deterministic result. Later, we will remove the lock in SkipList to further
- * enhance the performance. In this case, one should use the concurrent skip list (by
- * using michael-scott algorithm) instead of this simple version in a multi-thread
- * environment, to achieve higher performance of read/write operations.
- *
- * Note: Duplicated primary key situation.
- * In case of duplicated primary key, two ways can be employed to handle this situation:
- * 1. add as normal insertion with out special process.
- * 2. add an overflow pointer at each list node, all nodes with the same key will be added
- *    in the overflow pointer. In this case, the total steps of each search will be reduced significantly.
- *    Currently, we implement the skip list in a line with the first means, maybe refactor it soon.
- *
- *    Memory consumption: the memory alignment causes many memory wasted. So, employ a memory
- *    pool will significantly reduce the total memory consumption, as well as the calloc/malloc operation costs.
- *
- * 3. use the iterator pattern to refactor all routines to make it more clean
- */
-
-// state struct, record following information:
-// number of links in each level.
-// avg search steps, for latest 1000 queries
-// avg search rsp time, for latest 1000 queries
-// total memory size
-typedef struct tSkipListState {
-  // in bytes, sizeof(tSkipList)+sizeof(tSkipListNode)*tSkipList->nSize
-  uint64_t nTotalMemSize;
-  uint64_t nLevelNodeCnt[MAX_SKIP_LIST_LEVEL];
-  uint64_t queryCount;  // total query count
-
-  /*
-   * only record latest 1000 queries
-   * when the value==1000, = 0,
-   * nTotalStepsForQueries = 0,
-   * nTotalElapsedTimeForQueries = 0
-   */
-  uint64_t nRecQueries;
-  uint16_t nTotalStepsForQueries;
-  uint64_t nTotalElapsedTimeForQueries;
-
-  uint16_t nInsertObjs;
-  uint16_t nTotalStepsForInsert;
-  uint64_t nTotalElapsedTimeForInsert;
-} tSkipListState;
-
-typedef struct tSkipList {
-  tSkipListNode pHead;
-  uint64_t      nSize;
-  uint16_t      nMaxLevel;
-  uint16_t      nLevel;
-  uint16_t      keyType;
-  uint16_t      nMaxKeyLen;
-
-  __compar_fn_t    comparator;
-  pthread_rwlock_t lock;   // will be removed soon
-  tSkipListState   state;  // skiplist state
-} tSkipList;
-
-/*
- * iterate the skiplist
- * this will cause the multi-thread problem, when the skiplist is destroyed, the iterate may
- * continue iterating the skiplist, so add the reference count for skiplist
- * TODO add the ref for skiplist when one iterator is created
- */
-typedef struct SSkipListIterator {
-  tSkipList *    pSkipList;
-  tSkipListNode *cur;
-  int64_t        num;
-} SSkipListIterator;
-
-/*
- * query condition structure to denote the range query
- * todo merge the point query cond with range query condition
- */
-typedef struct tSKipListQueryCond {
-  // when the upper bounding == lower bounding, it is a point query
-  tSkipListKey lowerBnd;
-  tSkipListKey upperBnd;
-  int32_t      lowerBndRelOptr;  // relation operator to denote if lower bound is
-  int32_t      upperBndRelOptr;  // included or not
-} tSKipListQueryCond;
-
-tSkipList *SSkipListCreate(int16_t nMaxLevel, int16_t keyType, int16_t nMaxKeyLen);
-
-void *SSkipListDestroy(tSkipList *pSkipList);
-
-// create skip list key
-tSkipListKey SSkipListCreateKey(int32_t type, char *val, size_t keyLength);
-
-// destroy skip list key
-void tSkipListDestroyKey(tSkipListKey *pKey);
-
-// put data into skiplist
-tSkipListNode *SSkipListPut(tSkipList *pSkipList, void *pData, tSkipListKey *pKey, int32_t insertIdenticalKey);
-
-/*
- * get only *one* node of which key is equalled to pKey, even there are more
- * than one nodes are of the same key
- */
-tSkipListNode *tSkipListGetOne(tSkipList *pSkipList, tSkipListKey *pKey);
-
-/*
- * get all data with the same keys
- */
-int32_t tSkipListGets(tSkipList *pSkipList, tSkipListKey *pKey, tSkipListNode ***pRes);
-
-int32_t tSkipListIterateList(tSkipList *pSkipList, tSkipListNode ***pRes, bool (*fp)(tSkipListNode *, void *),
-                             void *param);
-
-/*
- * remove only one node of the pKey value.
- * If more than one node has the same value, any one will be removed
- *
- * @Return
- * true: one node has been removed
- * false: no node has been removed
- */
-bool tSkipListRemove(tSkipList *pSkipList, tSkipListKey *pKey);
-
-/*
- * remove the specified node in parameters
- */
-void tSkipListRemoveNode(tSkipList *pSkipList, tSkipListNode *pNode);
-
-// for debug purpose only
-void SSkipListPrint(tSkipList *pSkipList, int16_t nlevel);
-
-/*
- * range query & single point query function
- */
-int32_t tSkipListQuery(tSkipList *pSkipList, tSKipListQueryCond *pQueryCond, tSkipListNode ***pResult);
-
-/*
- * include/exclude point query
- */
-int32_t tSkipListPointQuery(tSkipList *pSkipList, tSkipListKey *pKey, int32_t numOfKey, tSkipListPointQueryType type,
-                            tSkipListNode ***pResult);
-
-int32_t tSkipListIteratorReset(tSkipList *pSkipList, SSkipListIterator *iter);
-bool tSkipListIteratorNext(SSkipListIterator *iter);
-tSkipListNode *tSkipListIteratorGet(SSkipListIterator *iter);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif  // TBASE_TSKIPLIST_H
-#endif
\ No newline at end of file

src/util/inc/tskiplist.h

@@ -185,15 +185,39 @@ SSkipListNode *tSkipListPut(SSkipList *pSkipList, SSkipListNode *pNode);
 SArray* tSkipListGet(SSkipList *pSkipList, SSkipListKey pKey, int16_t keyType);
 
 /**
- *
+ * get the size of skip list
  * @param pSkipList
- * @param pRes
- * @param fp
- * @param param
  * @return
  */
-int32_t tSkipListIterateList(SSkipList *pSkipList, SSkipListNode ***pRes, bool (*fp)(SSkipListNode *, void *),
-                             void *param);
+size_t tSkipListGetSize(const SSkipList* pSkipList);
+
+/**
+ * create skiplist iterator
+ * @param pSkipList
+ * @return
+ */
+SSkipListIterator* tSkipListCreateIter(SSkipList *pSkipList);
+
+/**
+ * forward the skip list iterator
+ * @param iter
+ * @return
+ */
+bool tSkipListIterNext(SSkipListIterator *iter);
+
+/**
+ * get the element of skip list node
+ * @param iter
+ * @return
+ */
+SSkipListNode *tSkipListIterGet(SSkipListIterator *iter);
+
+/**
+ * destroy the skip list node
+ * @param iter
+ * @return
+ */
+void* tSkipListDestroyIter(SSkipListIterator* iter);
 
 /*
  * remove only one node of the pKey value.
@@ -210,9 +234,6 @@ bool tSkipListRemove(SSkipList *pSkipList, SSkipListKey *pKey);
  */
 void tSkipListRemoveNode(SSkipList *pSkipList, SSkipListNode *pNode);
 
-int32_t        tSkipListIteratorReset(SSkipList *pSkipList, SSkipListIterator *iter);
-bool           tSkipListIteratorNext(SSkipListIterator *iter);
-SSkipListNode *tSkipListIteratorGet(SSkipListIterator *iter);
 
 #ifdef __cplusplus
 }

src/util/src/sskiplist.c

-/*
- * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
- *
- * This program is free software: you can use, redistribute, and/or modify
- * it under the terms of the GNU Affero General Public License, version 3
- * or later ("AGPL"), as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-
-#if 0
-#include "os.h"
-
-#include "tlog.h"
-#include "taosdef.h"
-#include "sskiplist.h"
-#include "tutil.h"
-
-static FORCE_INLINE void recordNodeEachLevel(tSkipList *pSkipList, int32_t nLevel) {  // record link count in each level
-  for (int32_t i = 0; i < nLevel; ++i) {
-    pSkipList->state.nLevelNodeCnt[i]++;
-  }
-}
-
-static FORCE_INLINE void removeNodeEachLevel(tSkipList *pSkipList, int32_t nLevel) {
-  for (int32_t i = 0; i < nLevel; ++i) {
-    pSkipList->state.nLevelNodeCnt[i]--;
-  }
-}
-
-static FORCE_INLINE int32_t getSkipListNodeRandomHeight(tSkipList *pSkipList) {
-  const uint32_t factor = 4;
-
-  int32_t n = 1;
-  while ((rand() % factor) == 0 && n <= pSkipList->nMaxLevel) {
-    n++;
-  }
-
-  return n;
-}
-
-static FORCE_INLINE int32_t getSkipListNodeLevel(tSkipList *pSkipList) {
-  int32_t nLevel = getSkipListNodeRandomHeight(pSkipList);
-  if (pSkipList->nSize == 0) {
-    nLevel = 1;
-    pSkipList->nLevel = 1;
-  } else {
-    if (nLevel > pSkipList->nLevel && pSkipList->nLevel < pSkipList->nMaxLevel) {
-      nLevel = (++pSkipList->nLevel);
-    }
-  }
-  return nLevel;
-}
-
-void tSkipListDoInsert(tSkipList *pSkipList, tSkipListNode **forward, int32_t nLevel, tSkipListNode *pNode);
-
-void SSkipListDoRecordPut(tSkipList *pSkipList) {
-  const int32_t MAX_RECORD_NUM = 1000;
-
-  if (pSkipList->state.nInsertObjs == MAX_RECORD_NUM) {
-    pSkipList->state.nInsertObjs = 1;
-    pSkipList->state.nTotalStepsForInsert = 0;
-    pSkipList->state.nTotalElapsedTimeForInsert = 0;
-  } else {
-    pSkipList->state.nInsertObjs++;
-  }
-}
-
-int32_t compareIntVal(const void *pLeft, const void *pRight) {
-  int64_t lhs = ((tSkipListKey *)pLeft)->i64Key;
-  int64_t rhs = ((tSkipListKey *)pRight)->i64Key;
-
-  DEFAULT_COMP(lhs, rhs);
-}
-
-int32_t scompareIntDoubleVal(const void *pLeft, const void *pRight) {
-  int64_t lhs = ((tSkipListKey *)pLeft)->i64Key;
-  double  rhs = ((tSkipListKey *)pRight)->dKey;
-  if (fabs(lhs - rhs) < FLT_EPSILON) {
-    return 0;
-  } else {
-    return (lhs > rhs) ? 1 : -1;
-  }
-}
-
-int32_t scompareDoubleIntVal(const void *pLeft, const void *pRight) {
-  double  lhs = ((tSkipListKey *)pLeft)->dKey;
-  int64_t rhs = ((tSkipListKey *)pRight)->i64Key;
-  if (fabs(lhs - rhs) < FLT_EPSILON) {
-    return 0;
-  } else {
-    return (lhs > rhs) ? 1 : -1;
-  }
-}
-
-int32_t scompareDoubleVal(const void *pLeft, const void *pRight) {
-  double ret = (((tSkipListKey *)pLeft)->dKey - ((tSkipListKey *)pRight)->dKey);
-  if (fabs(ret) < FLT_EPSILON) {
-    return 0;
-  } else {
-    return ret > 0 ? 1 : -1;
-  }
-}
-
-int32_t scompareStrVal(const void *pLeft, const void *pRight) {
-  tSkipListKey *pL = (tSkipListKey *)pLeft;
-  tSkipListKey *pR = (tSkipListKey *)pRight;
-
-  if (pL->nLen == 0 && pR->nLen == 0) {
-    return 0;
-  }
-
-  //handle only one-side bound compare situation, there is only lower bound or only upper bound
-  if (pL->nLen == -1) {
-    return 1;  // no lower bound, lower bound is minimum, always return -1;
-  } else if (pR->nLen == -1) {
-    return -1;  // no upper bound, upper bound is maximum situation, always return 1;
-  }
-
-  int32_t ret = strcmp(((tSkipListKey *)pLeft)->pz, ((tSkipListKey *)pRight)->pz);
-
-  if (ret == 0) {
-    return 0;
-  } else {
-    return ret > 0 ? 1 : -1;
-  }
-}
-
-int32_t scompareWStrVal(const void *pLeft, const void *pRight) {
-  tSkipListKey *pL = (tSkipListKey *)pLeft;
-  tSkipListKey *pR = (tSkipListKey *)pRight;
-
-  if (pL->nLen == 0 && pR->nLen == 0) {
-    return 0;
-  }
-
-  //handle only one-side bound compare situation, there is only lower bound or only upper bound
-  if (pL->nLen == -1) {
-    return 1;  // no lower bound, lower bound is minimum, always return -1;
-  } else if (pR->nLen == -1) {
-    return -1;  // no upper bound, upper bound is maximum situation, always return 1;
-  }
-
-  int32_t ret = wcscmp(((tSkipListKey *)pLeft)->wpz, ((tSkipListKey *)pRight)->wpz);
-
-  if (ret == 0) {
-    return 0;
-  } else {
-    return ret > 0 ? 1 : -1;
-  }
-}
-
-static __compar_fn_t getKeyFilterComparator(tSkipList *pSkipList, int32_t filterDataType) {
-  __compar_fn_t comparator = NULL;
-
-  switch (pSkipList->keyType) {
-    case TSDB_DATA_TYPE_TINYINT:
-    case TSDB_DATA_TYPE_SMALLINT:
-    case TSDB_DATA_TYPE_INT:
-    case TSDB_DATA_TYPE_BIGINT:
-    case TSDB_DATA_TYPE_BOOL: {
-      if (filterDataType >= TSDB_DATA_TYPE_BOOL && filterDataType <= TSDB_DATA_TYPE_BIGINT) {
-        comparator = compareIntVal;
-      } else if (filterDataType >= TSDB_DATA_TYPE_FLOAT && filterDataType <= TSDB_DATA_TYPE_DOUBLE) {
-        comparator = scompareIntDoubleVal;
-      }
-      break;
-    }
-    case TSDB_DATA_TYPE_FLOAT:
-    case TSDB_DATA_TYPE_DOUBLE: {
-      if (filterDataType >= TSDB_DATA_TYPE_BOOL && filterDataType <= TSDB_DATA_TYPE_BIGINT) {
-        comparator = scompareDoubleIntVal;
-      } else if (filterDataType >= TSDB_DATA_TYPE_FLOAT && filterDataType <= TSDB_DATA_TYPE_DOUBLE) {
-        comparator = scompareDoubleVal;
-      }
-      break;
-    }
-    case TSDB_DATA_TYPE_BINARY:
-      comparator = scompareStrVal;
-      break;
-    case TSDB_DATA_TYPE_NCHAR:
-      comparator = scompareWStrVal;
-      break;
-    default:
-      comparator = compareIntVal;
-      break;
-  }
-
-  return comparator;
-}
-
-static __compar_fn_t getKeyComparator(int32_t keyType) {
-  __compar_fn_t comparator = NULL;
-
-  switch (keyType) {
-    case TSDB_DATA_TYPE_TINYINT:
-    case TSDB_DATA_TYPE_SMALLINT:
-    case TSDB_DATA_TYPE_INT:
-    case TSDB_DATA_TYPE_BIGINT:
-    case TSDB_DATA_TYPE_BOOL:
-      comparator = compareIntVal;
-      break;
-
-    case TSDB_DATA_TYPE_FLOAT:
-    case TSDB_DATA_TYPE_DOUBLE:
-      comparator = scompareDoubleVal;
-      break;
-
-    case TSDB_DATA_TYPE_BINARY:
-      comparator = scompareStrVal;
-      break;
-
-    case TSDB_DATA_TYPE_NCHAR:
-      comparator = scompareWStrVal;
-      break;
-
-    default:
-      comparator = compareIntVal;
-      break;
-  }
-
-  return comparator;
-}
-
-tSkipList* SSkipListCreate(int16_t nMaxLevel, int16_t keyType, int16_t nMaxKeyLen) {
-  tSkipList *pSkipList = (tSkipList *)calloc(1, sizeof(tSkipList));
-  if (pSkipList == NULL) {
-    return NULL;
-  }
-
-  pSkipList->keyType = keyType;
-
-  pSkipList->comparator = getKeyComparator(keyType);
-  pSkipList->pHead.pForward = (tSkipListNode **)calloc(1, POINTER_BYTES * MAX_SKIP_LIST_LEVEL);
-
-  pSkipList->nMaxLevel = MAX_SKIP_LIST_LEVEL;
-  pSkipList->nLevel = 1;
-
-  pSkipList->nMaxKeyLen = nMaxKeyLen;
-  pSkipList->nMaxLevel = nMaxLevel;
-
-  if (pthread_rwlock_init(&pSkipList->lock, NULL) != 0) {
-    tfree(pSkipList->pHead.pForward);
-    tfree(pSkipList);
-    return NULL;
-  }
-
-  srand(time(NULL));
-  pSkipList->state.nTotalMemSize += sizeof(tSkipList);
-  return pSkipList;
-}
-
-static void doRemove(tSkipList *pSkipList, tSkipListNode *pNode, tSkipListNode *forward[]) {
-  int32_t level = pNode->nLevel;
-  for (int32_t j = level - 1; j >= 0; --j) {
-    if ((forward[j]->pForward[j] != NULL) && (forward[j]->pForward[j]->pForward[j])) {
-      forward[j]->pForward[j]->pForward[j]->pBackward[j] = forward[j];
-    }
-
-    if (forward[j]->pForward[j] != NULL) {
-      forward[j]->pForward[j] = forward[j]->pForward[j]->pForward[j];
-    }
-  }
-
-  pSkipList->state.nTotalMemSize -= (sizeof(tSkipListNode) + POINTER_BYTES * pNode->nLevel * 2);
-  removeNodeEachLevel(pSkipList, pNode->nLevel);
-
-  tfree(pNode);
-  --pSkipList->nSize;
-}
-
-static size_t getOneNodeSize(const tSkipListKey *pKey, int32_t nLevel) {
-  size_t size = sizeof(tSkipListNode) + sizeof(intptr_t) * (nLevel << 1);
-  if (pKey->nType == TSDB_DATA_TYPE_BINARY) {
-    size += pKey->nLen + 1;
-  } else if (pKey->nType == TSDB_DATA_TYPE_NCHAR) {
-    size += (pKey->nLen + 1) * TSDB_NCHAR_SIZE;
-  }
-
-  return size;
-}
-
-static tSkipListNode *SSkipListCreateNode(void *pData, const tSkipListKey *pKey, int32_t nLevel) {
-  size_t         nodeSize = getOneNodeSize(pKey, nLevel);
-  tSkipListNode *pNode = (tSkipListNode *)calloc(1, nodeSize);
-
-  pNode->pForward = (tSkipListNode **)(&pNode[1]);
-  pNode->pBackward = (pNode->pForward + nLevel);
-
-  pNode->pData = pData;
-
-  pNode->key = *pKey;
-  if (pKey->nType == TSDB_DATA_TYPE_BINARY) {
-    pNode->key.pz = (char *)(pNode->pBackward + nLevel);
-
-    strcpy(pNode->key.pz, pKey->pz);
-    pNode->key.pz[pKey->nLen] = 0;
-  } else if (pKey->nType == TSDB_DATA_TYPE_NCHAR) {
-    pNode->key.wpz = (wchar_t *)(pNode->pBackward + nLevel);
-    wcsncpy(pNode->key.wpz, pKey->wpz, pKey->nLen);
-    pNode->key.wpz[pKey->nLen] = 0;
-  }
-
-  pNode->nLevel = nLevel;
-  return pNode;
-}
-
-tSkipListKey SSkipListCreateKey(int32_t type, char *val, size_t keyLength) {
-  tSkipListKey k = {0};
-  tVariantCreateFromBinary(&k, val, (uint32_t) keyLength, (uint32_t) type);
-  return k;
-}
-
-void tSkipListDestroyKey(tSkipListKey *pKey) { tVariantDestroy(pKey); }
-
-void* SSkipListDestroy(tSkipList *pSkipList) {
-  if (pSkipList == NULL) {
-    return NULL;
-  }
-
-  pthread_rwlock_wrlock(&pSkipList->lock);
-  tSkipListNode *pNode = pSkipList->pHead.pForward[0];
-  while (pNode) {
-    tSkipListNode *pTemp = pNode;
-    pNode = pNode->pForward[0];
-    tfree(pTemp);
-  }
-
-  tfree(pSkipList->pHead.pForward);
-  pthread_rwlock_unlock(&pSkipList->lock);
-
-  pthread_rwlock_destroy(&pSkipList->lock);
-  tfree(pSkipList);
-
-  return NULL;
-}
-
-tSkipListNode *SSkipListPut(tSkipList *pSkipList, void *pData, tSkipListKey *pKey, int32_t insertIdenticalKey) {
-  if (pSkipList == NULL) {
-    return NULL;
-  }
-
-  pthread_rwlock_wrlock(&pSkipList->lock);
-
-  // record one node is put into skiplist
-  SSkipListDoRecordPut(pSkipList);
-
-  tSkipListNode *px = &pSkipList->pHead;
-
-  tSkipListNode *forward[MAX_SKIP_LIST_LEVEL] = {0};
-  for (int32_t i = pSkipList->nLevel - 1; i >= 0; --i) {
-    while (px->pForward[i] != NULL && (pSkipList->comparator(&px->pForward[i]->key, pKey) < 0)) {
-      px = px->pForward[i];
-    }
-
-    pSkipList->state.nTotalStepsForInsert++;
-    forward[i] = px;
-  }
-
-  // if the skiplist does not allowed identical key inserted, the new data will be discarded.
-  if ((insertIdenticalKey == 0) && forward[0] != &pSkipList->pHead &&
-      (pSkipList->comparator(&forward[0]->key, pKey) == 0)) {
-    pthread_rwlock_unlock(&pSkipList->lock);
-    return forward[0];
-  }
-
-  int32_t nLevel = getSkipListNodeLevel(pSkipList);
-  recordNodeEachLevel(pSkipList, nLevel);
-
-  tSkipListNode *pNode = SSkipListCreateNode(pData, pKey, nLevel);
-  tSkipListDoInsert(pSkipList, forward, nLevel, pNode);
-
-  pSkipList->nSize += 1;
-
-  //    char tmpstr[512] = {0};
-  //    tVariantToString(&pNode->key, tmpstr);
-  //    pTrace("skiplist:%p, node added, key:%s, total list len:%d", pSkipList,
-  //    tmpstr, pSkipList->nSize);
-
-  pSkipList->state.nTotalMemSize += getOneNodeSize(pKey, nLevel);
-  pthread_rwlock_unlock(&pSkipList->lock);
-
-  return pNode;
-}
-
-void tSkipListDoInsert(tSkipList *pSkipList, tSkipListNode **forward, int32_t nLevel, tSkipListNode *pNode) {
-  for (int32_t i = 0; i < nLevel; ++i) {
-    tSkipListNode *x = forward[i];
-    if (x != NULL) {
-      pNode->pBackward[i] = x;
-      if (x->pForward[i]) x->pForward[i]->pBackward[i] = pNode;
-
-      pNode->pForward[i] = x->pForward[i];
-      x->pForward[i] = pNode;
-    } else {
-      pSkipList->pHead.pForward[i] = pNode;
-      pNode->pBackward[i] = &(pSkipList->pHead);
-    }
-  }
-}
-
-tSkipListNode *tSkipListGetOne(tSkipList *pSkipList, tSkipListKey *pKey) {
-  int32_t sLevel = pSkipList->nLevel - 1;
-  int32_t ret = -1;
-
-  tSkipListNode *x = &pSkipList->pHead;
-
-  pthread_rwlock_rdlock(&pSkipList->lock);
-  pSkipList->state.queryCount++;
-
-  __compar_fn_t filterComparator = getKeyFilterComparator(pSkipList, pKey->nType);
-
-  for (int32_t i = sLevel; i >= 0; --i) {
-    while (x->pForward[i] != NULL && (ret = filterComparator(&x->pForward[i]->key, pKey)) < 0) {
-      x = x->pForward[i];
-    }
-
-    if (ret == 0) {
-      pthread_rwlock_unlock(&pSkipList->lock);
-      return x->pForward[i];
-    }
-  }
-
-  pthread_rwlock_unlock(&pSkipList->lock);
-  return NULL;
-}
-
-static int32_t tSkipListEndParQuery(tSkipList *pSkipList, tSkipListNode *pStartNode, tSkipListKey *pEndKey,
-                                    int32_t cond, tSkipListNode ***pRes) {
-  pthread_rwlock_rdlock(&pSkipList->lock);
-  tSkipListNode *p = pStartNode;
-  int32_t        numOfRes = 0;
-
-  __compar_fn_t filterComparator = getKeyFilterComparator(pSkipList, pEndKey->nType);
-  while (p != NULL) {
-    int32_t ret = filterComparator(&p->key, pEndKey);
-    if (ret > 0) {
-      break;
-    }
-
-    if (ret < 0) {
-      numOfRes++;
-      p = p->pForward[0];
-    } else if (ret == 0) {
-      if (cond == TSDB_RELATION_LESS_EQUAL) {
-        numOfRes++;
-        p = p->pForward[0];
-      } else {
-        break;
-      }
-    }
-  }
-
-  (*pRes) = (tSkipListNode **)malloc(POINTER_BYTES * numOfRes);
-  for (int32_t i = 0; i < numOfRes; ++i) {
-    (*pRes)[i] = pStartNode;
-    pStartNode = pStartNode->pForward[0];
-  }
-  pthread_rwlock_unlock(&pSkipList->lock);
-
-  return numOfRes;
-}
-
-/*
- * maybe return the copy of tSkipListNode would be better
- */
-int32_t tSkipListGets(tSkipList *pSkipList, tSkipListKey *pKey, tSkipListNode ***pRes) {
-  (*pRes) = NULL;
-
-  tSkipListNode *pNode = tSkipListGetOne(pSkipList, pKey);
-  if (pNode == NULL) {
-    return 0;
-  }
-
-  __compar_fn_t filterComparator = getKeyFilterComparator(pSkipList, pKey->nType);
-
-  // backward check if previous nodes are with the same value.
-  tSkipListNode *pPrev = pNode->pBackward[0];
-  while ((pPrev != &pSkipList->pHead) && filterComparator(&pPrev->key, pKey) == 0) {
-    pPrev = pPrev->pBackward[0];
-  }
-
-  return tSkipListEndParQuery(pSkipList, pPrev->pForward[0], &pNode->key, TSDB_RELATION_LESS_EQUAL, pRes);
-}
-
-static tSkipListNode *tSkipListParQuery(tSkipList *pSkipList, tSkipListKey *pKey, int32_t cond) {
-  int32_t sLevel = pSkipList->nLevel - 1;
-  int32_t ret = -1;
-
-  tSkipListNode *x = &pSkipList->pHead;
-  __compar_fn_t  filterComparator = getKeyFilterComparator(pSkipList, pKey->nType);
-
-  pthread_rwlock_rdlock(&pSkipList->lock);
-
-  if (cond == TSDB_RELATION_LARGE_EQUAL || cond == TSDB_RELATION_LARGE) {
-    for (int32_t i = sLevel; i >= 0; --i) {
-      while (x->pForward[i] != NULL && (ret = filterComparator(&x->pForward[i]->key, pKey)) < 0) {
-        x = x->pForward[i];
-      }
-    }
-
-    // backward check if previous nodes are with the same value.
-    if (cond == TSDB_RELATION_LARGE_EQUAL && ret == 0) {
-      tSkipListNode *pNode = x->pForward[0];
-      while ((pNode->pBackward[0] != &pSkipList->pHead) && (filterComparator(&pNode->pBackward[0]->key, pKey) == 0)) {
-        pNode = pNode->pBackward[0];
-      }
-      pthread_rwlock_unlock(&pSkipList->lock);
-      return pNode;
-    }
-
-    if (ret > 0 || cond == TSDB_RELATION_LARGE_EQUAL) {
-      pthread_rwlock_unlock(&pSkipList->lock);
-      return x->pForward[0];
-    } else {  // cond == TSDB_RELATION_LARGE && ret == 0
-      tSkipListNode *pn = x->pForward[0];
-      while (pn != NULL && filterComparator(&pn->key, pKey) == 0) {
-        pn = pn->pForward[0];
-      }
-      pthread_rwlock_unlock(&pSkipList->lock);
-      return pn;
-    }
-  }
-
-  pthread_rwlock_unlock(&pSkipList->lock);
-  return NULL;
-}
-
-int32_t tSkipListIterateList(tSkipList *pSkipList, tSkipListNode ***pRes, bool (*fp)(tSkipListNode *, void *),
-                             void *param) {
-  (*pRes) = (tSkipListNode **)calloc(1, POINTER_BYTES * pSkipList->nSize);
-  if (NULL == *pRes) {
-    pError("error skiplist %p, malloc failed", pSkipList);
-    return -1;
-  }
-  
-  pthread_rwlock_rdlock(&pSkipList->lock);
-  tSkipListNode *pStartNode = pSkipList->pHead.pForward[0];
-  int32_t        num = 0;
-
-  for (int32_t i = 0; i < pSkipList->nSize; ++i) {
-    if (pStartNode == NULL) {
-      pError("error skiplist %p, required length:%d, actual length:%d", pSkipList, pSkipList->nSize, i - 1);
-#ifdef _DEBUG_VIEW
-      SSkipListPrint(pSkipList, 1);
-#endif
-      break;
-    }
-
-    if (fp == NULL || (fp != NULL && fp(pStartNode, param) == true)) {
-      (*pRes)[num++] = pStartNode;
-    }
-
-    pStartNode = pStartNode->pForward[0];
-  }
-
-  pthread_rwlock_unlock(&pSkipList->lock);
-
-  if (num == 0) {
-    free(*pRes);
-    *pRes = NULL;
-  } else if (num < pSkipList->nSize) { // free unused memory
-    char* tmp = realloc((*pRes), num * POINTER_BYTES);
-    assert(tmp != NULL);
-
-    *pRes = (tSkipListNode**)tmp;
-  }
-
-  return num;
-}
-
-int32_t tSkipListIteratorReset(tSkipList *pSkipList, SSkipListIterator* iter) {
-  if (pSkipList == NULL) {
-    return -1;
-  }
-
-  iter->pSkipList = pSkipList;
-
-  pthread_rwlock_rdlock(&pSkipList->lock);
-  iter->cur = NULL;//pSkipList->pHead.pForward[0];
-  iter->num = pSkipList->nSize;
-  pthread_rwlock_unlock(&pSkipList->lock);
-
-  return 0;
-}
-
-bool tSkipListIteratorNext(SSkipListIterator* iter) {
-  if (iter->num == 0 || iter->pSkipList == NULL) {
-    return false;
-  }
-
-  tSkipList* pSkipList = iter->pSkipList;
-
-  pthread_rwlock_rdlock(&pSkipList->lock);
-  if (iter->cur == NULL) {
-    iter->cur = pSkipList->pHead.pForward[0];
-  } else {
-    iter->cur = iter->cur->pForward[0];
-  }
-
-  pthread_rwlock_unlock(&pSkipList->lock);
-
-  return iter->cur != NULL;
-}
-
-tSkipListNode* tSkipListIteratorGet(SSkipListIterator* iter) {
-  return iter->cur;
-}
-
-int32_t tSkipListRangeQuery(tSkipList *pSkipList, tSKipListQueryCond *pCond, tSkipListNode ***pRes) {
-  pSkipList->state.queryCount++;
-  tSkipListNode *pStart = tSkipListParQuery(pSkipList, &pCond->lowerBnd, pCond->lowerBndRelOptr);
-  if (pStart == 0) {
-    *pRes = NULL;
-    return 0;
-  }
-
-  return tSkipListEndParQuery(pSkipList, pStart, &pCond->upperBnd, pCond->upperBndRelOptr, pRes);
-}
-
-static bool removeSupport(tSkipList *pSkipList, tSkipListNode **forward, tSkipListKey *pKey) {
-  __compar_fn_t filterComparator = getKeyFilterComparator(pSkipList, pKey->nType);
-
-  if (filterComparator(&forward[0]->pForward[0]->key, pKey) == 0) {
-    tSkipListNode *p = forward[0]->pForward[0];
-    doRemove(pSkipList, p, forward);
-  } else {  // failed to find the node of specified value,abort
-    return false;
-  }
-
-  // compress the minimum level of skip list
-  while (pSkipList->nLevel > 0 && pSkipList->pHead.pForward[pSkipList->nLevel - 1] == NULL) {
-    pSkipList->nLevel -= 1;
-  }
-
-  return true;
-}
-
-void tSkipListRemoveNode(tSkipList *pSkipList, tSkipListNode *pNode) {
-  tSkipListNode *forward[MAX_SKIP_LIST_LEVEL] = {0};
-
-  pthread_rwlock_rdlock(&pSkipList->lock);
-  for (int32_t i = 0; i < pNode->nLevel; ++i) {
-    forward[i] = pNode->pBackward[i];
-  }
-
-  removeSupport(pSkipList, forward, &pNode->key);
-  pthread_rwlock_unlock(&pSkipList->lock);
-}
-
-bool tSkipListRemove(tSkipList *pSkipList, tSkipListKey *pKey) {
-  tSkipListNode *forward[MAX_SKIP_LIST_LEVEL] = {0};
-  __compar_fn_t  filterComparator = getKeyFilterComparator(pSkipList, pKey->nType);
-
-  pthread_rwlock_rdlock(&pSkipList->lock);
-
-  tSkipListNode *x = &pSkipList->pHead;
-  for (int32_t i = pSkipList->nLevel - 1; i >= 0; --i) {
-    while (x->pForward[i] != NULL && (filterComparator(&x->pForward[i]->key, pKey) < 0)) {
-      x = x->pForward[i];
-    }
-    forward[i] = x;
-  }
-
-  bool ret = removeSupport(pSkipList, forward, pKey);
-  pthread_rwlock_unlock(&pSkipList->lock);
-
-  return ret;
-}
-
-void SSkipListPrint(tSkipList *pSkipList, int16_t nlevel) {
-  if (pSkipList == NULL || pSkipList->nLevel < nlevel || nlevel <= 0) {
-    return;
-  }
-
-  tSkipListNode *p = pSkipList->pHead.pForward[nlevel - 1];
-  int32_t        id = 1;
-  while (p) {
-    switch (pSkipList->keyType) {
-      case TSDB_DATA_TYPE_INT:
-      case TSDB_DATA_TYPE_SMALLINT:
-      case TSDB_DATA_TYPE_TINYINT:
-      case TSDB_DATA_TYPE_BIGINT:
-        fprintf(stdout, "%d: %" PRId64 " \n", id++, p->key.i64Key);
-        break;
-      case TSDB_DATA_TYPE_BINARY:
-        fprintf(stdout, "%d: %s \n", id++, p->key.pz);
-        break;
-      case TSDB_DATA_TYPE_DOUBLE:
-        fprintf(stdout, "%d: %lf \n", id++, p->key.dKey);
-        break;
-      default:
-        fprintf(stdout, "\n");
-    }
-    p = p->pForward[nlevel - 1];
-  }
-}
-
-/*
- * query processor based on query condition
- */
-int32_t tSkipListQuery(tSkipList *pSkipList, tSKipListQueryCond *pQueryCond, tSkipListNode ***pResult) {
-  // query condition check
-  int32_t       rel = 0;
-  __compar_fn_t comparator = getKeyComparator(pQueryCond->lowerBnd.nType);
-
-  if (pSkipList == NULL || pQueryCond == NULL || pSkipList->nSize == 0 ||
-      (((rel = comparator(&pQueryCond->lowerBnd, &pQueryCond->upperBnd)) > 0 &&
-        pQueryCond->lowerBnd.nType != TSDB_DATA_TYPE_NCHAR && pQueryCond->lowerBnd.nType != TSDB_DATA_TYPE_BINARY))) {
-    (*pResult) = NULL;
-    return 0;
-  }
-
-  if (rel == 0) {
-    /*
-     * 0 means: pQueryCond->lowerBnd == pQueryCond->upperBnd
-     * point query
-     */
-    if (pQueryCond->lowerBndRelOptr == TSDB_RELATION_LARGE_EQUAL &&
-        pQueryCond->upperBndRelOptr == TSDB_RELATION_LESS_EQUAL) {  // point query
-      return tSkipListGets(pSkipList, &pQueryCond->lowerBnd, pResult);
-    } else {
-      (*pResult) = NULL;
-      return 0;
-    }
-  } else {
-    /* range query, query operation code check */
-    return tSkipListRangeQuery(pSkipList, pQueryCond, pResult);
-  }
-}
-
-typedef struct MultipleQueryResult {
-  int32_t         len;
-  tSkipListNode **pData;
-} MultipleQueryResult;
-
-static int32_t mergeQueryResult(MultipleQueryResult *pResults, int32_t numOfResSet, tSkipListNode ***pRes) {
-  int32_t total = 0;
-  for (int32_t i = 0; i < numOfResSet; ++i) {
-    total += pResults[i].len;
-  }
-
-  (*pRes) = malloc(POINTER_BYTES * total);
-  int32_t idx = 0;
-
-  for (int32_t i = 0; i < numOfResSet; ++i) {
-    MultipleQueryResult *pOneResult = &pResults[i];
-    for (int32_t j = 0; j < pOneResult->len; ++j) {
-      (*pRes)[idx++] = pOneResult->pData[j];
-    }
-  }
-
-  return total;
-}
-
-static void removeDuplicateKey(tSkipListKey *pKey, int32_t *numOfKey, __compar_fn_t comparator) {
-  if (*numOfKey == 1) {
-    return;
-  }
-
-  qsort(pKey, *numOfKey, sizeof(pKey[0]), comparator);
-  int32_t i = 0, j = 1;
-
-  while (i < (*numOfKey) && j < (*numOfKey)) {
-    int32_t ret = comparator(&pKey[i], &pKey[j]);
-    if (ret == 0) {
-      j++;
-    } else {
-      pKey[i + 1] = pKey[j];
-      i++;
-      j++;
-    }
-  }
-
-  (*numOfKey) = i + 1;
-}
-
-int32_t mergeResult(const tSkipListKey *pKey, int32_t numOfKey, tSkipListNode ***pRes, __compar_fn_t comparator,
-                    tSkipListNode *pNode) {
-  int32_t i = 0, j = 0;
-  // merge two sorted arrays in O(n) time
-  while (i < numOfKey && pNode != NULL) {
-    int32_t ret = comparator(&pNode->key, &pKey[i]);
-    if (ret < 0) {
-      (*pRes)[j++] = pNode;
-      pNode = pNode->pForward[0];
-    } else if (ret == 0) {
-      pNode = pNode->pForward[0];
-    } else {  // pNode->key > pkey[i]
-      i++;
-    }
-  }
-
-  while (pNode != NULL) {
-    (*pRes)[j++] = pNode;
-    pNode = pNode->pForward[0];
-  }
-  return j;
-}
-
-int32_t tSkipListPointQuery(tSkipList *pSkipList, tSkipListKey *pKey, int32_t numOfKey, tSkipListPointQueryType type,
-                            tSkipListNode ***pRes) {
-  if (numOfKey == 0 || pKey == NULL || pSkipList == NULL || pSkipList->nSize == 0 ||
-      (type != INCLUDE_POINT_QUERY && type != EXCLUDE_POINT_QUERY)) {
-    (*pRes) = NULL;
-    return 0;
-  }
-
-  __compar_fn_t comparator = getKeyComparator(pKey->nType);
-  removeDuplicateKey(pKey, &numOfKey, comparator);
-
-  if (type == INCLUDE_POINT_QUERY) {
-    if (numOfKey == 1) {
-      return tSkipListGets(pSkipList, &pKey[0], pRes);
-    } else {
-      MultipleQueryResult *pTempResult = (MultipleQueryResult *)malloc(sizeof(MultipleQueryResult) * numOfKey);
-      for (int32_t i = 0; i < numOfKey; ++i) {
-        pTempResult[i].len = tSkipListGets(pSkipList, &pKey[i], &pTempResult[i].pData);
-      }
-      int32_t num = mergeQueryResult(pTempResult, numOfKey, pRes);
-
-      for (int32_t i = 0; i < numOfKey; ++i) {
-        free(pTempResult[i].pData);
-      }
-      free(pTempResult);
-      return num;
-    }
-  } else {  // exclude query
-    *pRes = malloc(POINTER_BYTES * pSkipList->nSize);
-
-    __compar_fn_t filterComparator = getKeyFilterComparator(pSkipList, pKey->nType);
-
-    tSkipListNode *pNode = pSkipList->pHead.pForward[0];
-    int32_t        retLen = mergeResult(pKey, numOfKey, pRes, filterComparator, pNode);
-
-    if (retLen < pSkipList->nSize) {
-      (*pRes) = realloc(*pRes, POINTER_BYTES * retLen);
-    }
-    return retLen;
-  }
-}
-
-#endif
\ No newline at end of file

src/util/src/tskiplist.c

@@ -524,6 +524,71 @@ SArray* tSkipListGet(SSkipList *pSkipList, SSkipListKey pKey, int16_t keyType) {
   return sa;
 }
 
+size_t tSkipListGetSize(const SSkipList* pSkipList) {
+  if (pSkipList == NULL) {
+    return 0;
+  }
+  
+  return pSkipList->size;
+}
+
+SSkipListIterator* tSkipListCreateIter(SSkipList *pSkipList) {
+  if (pSkipList == NULL) {
+    return NULL;
+  }
+  
+  SSkipListIterator* iter = calloc(1, sizeof(SSkipListIterator));
+  
+  iter->pSkipList = pSkipList;
+  if (pSkipList->lock) {
+    pthread_rwlock_rdlock(pSkipList->lock);
+  }
+  
+  iter->cur = NULL;
+  iter->num = pSkipList->size;
+  
+  if (pSkipList->lock) {
+    pthread_rwlock_unlock(pSkipList->lock);
+  }
+  
+  return iter;
+}
+
+bool tSkipListIterNext(SSkipListIterator *iter) {
+  if (iter->num == 0 || iter->pSkipList == NULL) {
+    return false;
+  }
+  
+  SSkipList *pSkipList = iter->pSkipList;
+  
+  if (pSkipList->lock) {
+    pthread_rwlock_rdlock(pSkipList->lock);
+  }
+  
+  if (iter->cur == NULL) {
+    iter->cur = SL_GET_FORWARD_POINTER(pSkipList->pHead, 0);
+  } else {
+    iter->cur = SL_GET_FORWARD_POINTER(iter->cur, 0);
+  }
+  
+  if (pSkipList->lock) {
+    pthread_rwlock_unlock(pSkipList->lock);
+  }
+  
+  return iter->cur != NULL;
+}
+
+SSkipListNode *tSkipListIterGet(SSkipListIterator *iter) { return (iter == NULL)? NULL:iter->cur; }
+
+void* tSkipListDestroyIter(SSkipListIterator* iter) {
+  if (iter == NULL) {
+    return NULL;
+  }
+  
+  tfree(iter);
+  return NULL;
+}
+
 // static int32_t tSkipListEndParQuery(SSkipList *pSkipList, SSkipListNode *pStartNode, SSkipListKey *pEndKey,
 //                                    int32_t cond, SSkipListNode ***pRes) {
 //  pthread_rwlock_rdlock(&pSkipList->lock);