diff --git a/source/libs/index/inc/index_cache.h b/source/libs/index/inc/indexCache.h
similarity index 96%
rename from source/libs/index/inc/index_cache.h
rename to source/libs/index/inc/indexCache.h
index 086e75d99f..3ea986ad48 100644
--- a/source/libs/index/inc/index_cache.h
+++ b/source/libs/index/inc/indexCache.h
@@ -1,6 +1,5 @@
 /*
- * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
- *
+ * 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.
@@ -16,7 +15,7 @@
 #define __INDEX_CACHE_H__
 
 #include "indexInt.h"
-#include "index_util.h"
+#include "indexUtil.h"
 #include "tskiplist.h"
 
 // ----------------- key structure in skiplist ---------------------
diff --git a/source/libs/index/inc/index_comm.h b/source/libs/index/inc/indexComm.h
similarity index 100%
rename from source/libs/index/inc/index_comm.h
rename to source/libs/index/inc/indexComm.h
diff --git a/source/libs/index/inc/index_fst.h b/source/libs/index/inc/indexFst.h
similarity index 98%
rename from source/libs/index/inc/index_fst.h
rename to source/libs/index/inc/indexFst.h
index b131aa0d9d..39ad5ffa8c 100644
--- a/source/libs/index/inc/index_fst.h
+++ b/source/libs/index/inc/indexFst.h
@@ -20,12 +20,12 @@
 extern "C" {
 #endif
 
+#include "indexFstAutomation.h"
+#include "indexFstCountingWriter.h"
+#include "indexFstNode.h"
+#include "indexFstRegistry.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_fst_automation.h"
-#include "index_fst_counting_writer.h"
-#include "index_fst_node.h"
-#include "index_fst_registry.h"
-#include "index_fst_util.h"
 
 #define OUTPUT_PREFIX(a, b) ((a) > (b) ? (b) : (a)
 
diff --git a/source/libs/index/inc/index_fst_automation.h b/source/libs/index/inc/indexFstAutomation.h
similarity index 98%
rename from source/libs/index/inc/index_fst_automation.h
rename to source/libs/index/inc/indexFstAutomation.h
index 786d3eb7d2..3a0f74ee76 100644
--- a/source/libs/index/inc/index_fst_automation.h
+++ b/source/libs/index/inc/indexFstAutomation.h
@@ -19,8 +19,8 @@
 extern "C" {
 #endif
 
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_fst_util.h"
 
 typedef struct AutomationCtx AutomationCtx;
 
diff --git a/source/libs/index/inc/index_fst_common.h b/source/libs/index/inc/indexFstCommon.h
similarity index 100%
rename from source/libs/index/inc/index_fst_common.h
rename to source/libs/index/inc/indexFstCommon.h
diff --git a/source/libs/index/inc/index_fst_counting_writer.h b/source/libs/index/inc/indexFstCountingWriter.h
similarity index 100%
rename from source/libs/index/inc/index_fst_counting_writer.h
rename to source/libs/index/inc/indexFstCountingWriter.h
diff --git a/source/libs/index/inc/index_fst_node.h b/source/libs/index/inc/indexFstNode.h
similarity index 96%
rename from source/libs/index/inc/index_fst_node.h
rename to source/libs/index/inc/indexFstNode.h
index 4dbf4cea04..4bbc739c73 100644
--- a/source/libs/index/inc/index_fst_node.h
+++ b/source/libs/index/inc/indexFstNode.h
@@ -20,9 +20,9 @@
 extern "C" {
 #endif
 
+#include "indexFstCountingWriter.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_fst_counting_writer.h"
-#include "index_fst_util.h"
 
 #define FST_BUILDER_NODE_IS_FINAL(bn) (bn->isFinal)
 #define FST_BUILDER_NODE_TRANS_ISEMPTY(bn) (taosArrayGetSize(bn->trans) == 0)
diff --git a/source/libs/index/inc/index_fst_registry.h b/source/libs/index/inc/indexFstRegistry.h
similarity index 97%
rename from source/libs/index/inc/index_fst_registry.h
rename to source/libs/index/inc/indexFstRegistry.h
index 20b70e2866..09cde6c131 100644
--- a/source/libs/index/inc/index_fst_registry.h
+++ b/source/libs/index/inc/indexFstRegistry.h
@@ -19,9 +19,9 @@
 extern "C" {
 #endif
 
+#include "indexFstNode.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_fst_node.h"
-#include "index_fst_util.h"
 
 typedef struct FstRegistryCell {
   CompiledAddr    addr;
diff --git a/source/libs/index/inc/index_fst_util.h b/source/libs/index/inc/indexFstUtil.h
similarity index 99%
rename from source/libs/index/inc/index_fst_util.h
rename to source/libs/index/inc/indexFstUtil.h
index f173dd9a15..d0bbc923d1 100644
--- a/source/libs/index/inc/index_fst_util.h
+++ b/source/libs/index/inc/indexFstUtil.h
@@ -20,8 +20,8 @@
 extern "C" {
 #endif
 
+#include "indexFstCommon.h"
 #include "indexInt.h"
-#include "index_fst_common.h"
 
 typedef uint64_t FstType;
 typedef uint64_t CompiledAddr;
diff --git a/source/libs/index/inc/indexSparse.h b/source/libs/index/inc/indexSparse.h
new file mode 100644
index 0000000000..8035f6e08d
--- /dev/null
+++ b/source/libs/index/inc/indexSparse.h
@@ -0,0 +1,43 @@
+/*
+ * 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/>.
+ */
+
+#ifndef _TD_INDEX_SPARSE_H_
+#define _TD_INDEX_SPARSE_H_
+
+#include "tarray.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct FstSparseSet {
+  SArray *dense;
+  SArray *sparse;
+  int32_t size;
+} FstSparseSet;
+
+FstSparseSet *sparSetCreate(int32_t sz);
+void          sparSetDestroy(FstSparseSet *s);
+uint32_t      sparSetLen(FstSparseSet *ss);
+uint32_t      sparSetAdd(FstSparseSet *ss, uint32_t ip);
+uint32_t      sparSetGet(FstSparseSet *ss, uint32_t i);
+bool          sparSetContains(FstSparseSet *ss, uint32_t ip);
+void          sparSetClear(FstSparseSet *ss);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/source/libs/index/inc/index_tfile.h b/source/libs/index/inc/indexTfile.h
similarity index 97%
rename from source/libs/index/inc/index_tfile.h
rename to source/libs/index/inc/indexTfile.h
index 3794898d3a..9712e4b30f 100644
--- a/source/libs/index/inc/index_tfile.h
+++ b/source/libs/index/inc/indexTfile.h
@@ -15,11 +15,11 @@
 #ifndef __INDEX_TFILE_H__
 #define __INDEX_TFILE_H__
 
+#include "indexFst.h"
+#include "indexFstCountingWriter.h"
 #include "indexInt.h"
-#include "index_fst.h"
-#include "index_fst_counting_writer.h"
-#include "index_tfile.h"
-#include "index_util.h"
+#include "indexTfile.h"
+#include "indexUtil.h"
 #include "tlockfree.h"
 
 #ifdef __cplusplus
diff --git a/source/libs/index/inc/index_util.h b/source/libs/index/inc/indexUtil.h
similarity index 100%
rename from source/libs/index/inc/index_util.h
rename to source/libs/index/inc/indexUtil.h
diff --git a/source/libs/index/src/index.c b/source/libs/index/src/index.c
index 61dd952381..d3ca3a1acf 100644
--- a/source/libs/index/src/index.c
+++ b/source/libs/index/src/index.c
@@ -14,11 +14,11 @@
  */
 
 #include "index.h"
+#include "indexCache.h"
+#include "indexComm.h"
 #include "indexInt.h"
-#include "index_cache.h"
-#include "index_comm.h"
-#include "index_tfile.h"
-#include "index_util.h"
+#include "indexTfile.h"
+#include "indexUtil.h"
 #include "tdef.h"
 #include "tsched.h"
 
@@ -236,11 +236,11 @@ int indexDelete(SIndex* index, SIndexMultiTermQuery* query) {
 
   return 1;
 }
-int indexRebuild(SIndex* index, SIndexOpts* opts){
+int indexRebuild(SIndex* index, SIndexOpts* opts) {
 #ifdef USE_INVERTED_INDEX
 #endif
 
-    return 0;
+  return 0;
 }
 
 SIndexOpts* indexOptsCreate() {
diff --git a/source/libs/index/src/index_cache.c b/source/libs/index/src/indexCache.c
similarity index 99%
rename from source/libs/index/src/index_cache.c
rename to source/libs/index/src/indexCache.c
index bf907726bc..ca26cf38e5 100644
--- a/source/libs/index/src/index_cache.c
+++ b/source/libs/index/src/indexCache.c
@@ -13,9 +13,9 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "index_cache.h"
-#include "index_comm.h"
-#include "index_util.h"
+#include "indexCache.h"
+#include "indexComm.h"
+#include "indexUtil.h"
 #include "tcompare.h"
 #include "tsched.h"
 
diff --git a/source/libs/index/src/index_comm.c b/source/libs/index/src/indexComm.c
similarity index 100%
rename from source/libs/index/src/index_comm.c
rename to source/libs/index/src/indexComm.c
diff --git a/source/libs/index/src/index_fst.c b/source/libs/index/src/indexFst.c
similarity index 99%
rename from source/libs/index/src/index_fst.c
rename to source/libs/index/src/indexFst.c
index eaefaca887..24bc7a93a2 100644
--- a/source/libs/index/src/index_fst.c
+++ b/source/libs/index/src/indexFst.c
@@ -13,9 +13,9 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "index_fst.h"
+#include "indexFst.h"
+#include "indexFstAutomation.h"
 #include "indexInt.h"
-#include "index_fst_automation.h"
 #include "tchecksum.h"
 #include "tcoding.h"
 
diff --git a/source/libs/index/src/index_fst_automation.c b/source/libs/index/src/indexFstAutomation.c
similarity index 99%
rename from source/libs/index/src/index_fst_automation.c
rename to source/libs/index/src/indexFstAutomation.c
index 20e981559d..0702e3b94e 100644
--- a/source/libs/index/src/index_fst_automation.c
+++ b/source/libs/index/src/indexFstAutomation.c
@@ -13,7 +13,7 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "index_fst_automation.h"
+#include "indexFstAutomation.h"
 
 StartWithStateValue* startWithStateValueCreate(StartWithStateKind kind, ValueType ty, void* val) {
   StartWithStateValue* sv = taosMemoryCalloc(1, sizeof(StartWithStateValue));
diff --git a/source/libs/index/src/index_fst_common.c b/source/libs/index/src/indexFstCommon.c
similarity index 74%
rename from source/libs/index/src/index_fst_common.c
rename to source/libs/index/src/indexFstCommon.c
index 2d7586e8d9..e2544c7ac3 100644
--- a/source/libs/index/src/index_fst_common.c
+++ b/source/libs/index/src/indexFstCommon.c
@@ -12,7 +12,7 @@
  * 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/>.
  */
-#include "index_fst_common.h"
+#include "indexFstCommon.h"
 
 const uint8_t COMMON_INPUTS[] = {
     84,   // '\x00'
@@ -274,20 +274,23 @@ const uint8_t COMMON_INPUTS[] = {
 };
 
 const char COMMON_INPUTS_INV[] = {
-    't',    'e',    '/',    'o',    'a',    's',    'r',    'i',    'p',    'c',    'n',    'w',    '.',    'h',    'l',    'm',
-    '-',    'd',    'u',    '0',    '1',    '2',    'g',    '=',    ':',    'b',    'f',    '3',    'y',    '5',    '&',    '_',
-    '4',    'v',    '9',    '6',    '7',    '8',    'k',    '%',    '?',    'x',    'C',    'D',    'A',    'S',    'F',    'I',
-    'B',    'E',    'j',    'P',    'T',    'z',    'R',    'N',    'M',    '+',    'L',    'O',    'q',    'H',    'G',    'W',
-    'U',    'V',    ',',    'Y',    'K',    'J',    'Z',    'X',    'Q',    ';',    ')',    '(',    '~',    '[',    ']',    '$',
-    '!',    '\'',   '*',    '@',    '\x00', '\x01', '\x02', '\x03', '\x04', '\x05', '\x06', '\x07', '\x08', '\t',   '\n',   '\x0b',
-    '\x0c', '\r',   '\x0e', '\x0f', '\x10', '\x11', '\x12', '\x13', '\x14', '\x15', '\x16', '\x17', '\x18', '\x19', '\x1a', '\x1b',
-    '\x1c', '\x1d', '\x1e', '\x1f', ' ',    '"',    '#',    '<',    '>',    '\\',   '^',    '`',    '{',    '|',    '}',    '\x7f',
-    '\x80', '\x81', '\x82', '\x83', '\x84', '\x85', '\x86', '\x87', '\x88', '\x89', '\x8a', '\x8b', '\x8c', '\x8d', '\x8e', '\x8f',
-    '\x90', '\x91', '\x92', '\x93', '\x94', '\x95', '\x96', '\x97', '\x98', '\x99', '\x9a', '\x9b', '\x9c', '\x9d', '\x9e', '\x9f',
-    '\xa0', '\xa1', '\xa2', '\xa3', '\xa4', '\xa5', '\xa6', '\xa7', '\xa8', '\xa9', '\xaa', '\xab', '\xac', '\xad', '\xae', '\xaf',
-    '\xb0', '\xb1', '\xb2', '\xb3', '\xb4', '\xb5', '\xb6', '\xb7', '\xb8', '\xb9', '\xba', '\xbb', '\xbc', '\xbd', '\xbe', '\xbf',
-    '\xc0', '\xc1', '\xc2', '\xc3', '\xc4', '\xc5', '\xc6', '\xc7', '\xc8', '\xc9', '\xca', '\xcb', '\xcc', '\xcd', '\xce', '\xcf',
-    '\xd0', '\xd1', '\xd2', '\xd3', '\xd4', '\xd5', '\xd6', '\xd7', '\xd8', '\xd9', '\xda', '\xdb', '\xdc', '\xdd', '\xde', '\xdf',
-    '\xe0', '\xe1', '\xe2', '\xe3', '\xe4', '\xe5', '\xe6', '\xe7', '\xe8', '\xe9', '\xea', '\xeb', '\xec', '\xed', '\xee', '\xef',
-    '\xf0', '\xf1', '\xf2', '\xf3', '\xf4', '\xf5', '\xf6', '\xf7', '\xf8', '\xf9', '\xfa', '\xfb', '\xfc', '\xfd', '\xfe', '\xff',
+    't',    'e',    '/',    'o',    'a',    's',    'r',    'i',    'p',    'c',    'n',    'w',    '.',    'h',
+    'l',    'm',    '-',    'd',    'u',    '0',    '1',    '2',    'g',    '=',    ':',    'b',    'f',    '3',
+    'y',    '5',    '&',    '_',    '4',    'v',    '9',    '6',    '7',    '8',    'k',    '%',    '?',    'x',
+    'C',    'D',    'A',    'S',    'F',    'I',    'B',    'E',    'j',    'P',    'T',    'z',    'R',    'N',
+    'M',    '+',    'L',    'O',    'q',    'H',    'G',    'W',    'U',    'V',    ',',    'Y',    'K',    'J',
+    'Z',    'X',    'Q',    ';',    ')',    '(',    '~',    '[',    ']',    '$',    '!',    '\'',   '*',    '@',
+    '\x00', '\x01', '\x02', '\x03', '\x04', '\x05', '\x06', '\x07', '\x08', '\t',   '\n',   '\x0b', '\x0c', '\r',
+    '\x0e', '\x0f', '\x10', '\x11', '\x12', '\x13', '\x14', '\x15', '\x16', '\x17', '\x18', '\x19', '\x1a', '\x1b',
+    '\x1c', '\x1d', '\x1e', '\x1f', ' ',    '"',    '#',    '<',    '>',    '\\',   '^',    '`',    '{',    '|',
+    '}',    '\x7f', '\x80', '\x81', '\x82', '\x83', '\x84', '\x85', '\x86', '\x87', '\x88', '\x89', '\x8a', '\x8b',
+    '\x8c', '\x8d', '\x8e', '\x8f', '\x90', '\x91', '\x92', '\x93', '\x94', '\x95', '\x96', '\x97', '\x98', '\x99',
+    '\x9a', '\x9b', '\x9c', '\x9d', '\x9e', '\x9f', '\xa0', '\xa1', '\xa2', '\xa3', '\xa4', '\xa5', '\xa6', '\xa7',
+    '\xa8', '\xa9', '\xaa', '\xab', '\xac', '\xad', '\xae', '\xaf', '\xb0', '\xb1', '\xb2', '\xb3', '\xb4', '\xb5',
+    '\xb6', '\xb7', '\xb8', '\xb9', '\xba', '\xbb', '\xbc', '\xbd', '\xbe', '\xbf', '\xc0', '\xc1', '\xc2', '\xc3',
+    '\xc4', '\xc5', '\xc6', '\xc7', '\xc8', '\xc9', '\xca', '\xcb', '\xcc', '\xcd', '\xce', '\xcf', '\xd0', '\xd1',
+    '\xd2', '\xd3', '\xd4', '\xd5', '\xd6', '\xd7', '\xd8', '\xd9', '\xda', '\xdb', '\xdc', '\xdd', '\xde', '\xdf',
+    '\xe0', '\xe1', '\xe2', '\xe3', '\xe4', '\xe5', '\xe6', '\xe7', '\xe8', '\xe9', '\xea', '\xeb', '\xec', '\xed',
+    '\xee', '\xef', '\xf0', '\xf1', '\xf2', '\xf3', '\xf4', '\xf5', '\xf6', '\xf7', '\xf8', '\xf9', '\xfa', '\xfb',
+    '\xfc', '\xfd', '\xfe', '\xff',
 };
diff --git a/source/libs/index/src/index_fst_counting_writer.c b/source/libs/index/src/indexFstCountingWriter.c
similarity index 94%
rename from source/libs/index/src/index_fst_counting_writer.c
rename to source/libs/index/src/indexFstCountingWriter.c
index 6a161ba7e9..76ff4309b5 100644
--- a/source/libs/index/src/index_fst_counting_writer.c
+++ b/source/libs/index/src/indexFstCountingWriter.c
@@ -13,10 +13,10 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "os.h"
-#include "index_fst_counting_writer.h"
+#include "indexFstCountingWriter.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_fst_util.h"
+#include "os.h"
 #include "tutil.h"
 
 static int writeCtxDoWrite(WriterCtx* ctx, uint8_t* buf, int len) {
@@ -82,7 +82,9 @@ static int writeCtxDoFlush(WriterCtx* ctx) {
 
 WriterCtx* writerCtxCreate(WriterType type, const char* path, bool readOnly, int32_t capacity) {
   WriterCtx* ctx = taosMemoryCalloc(1, sizeof(WriterCtx));
-  if (ctx == NULL) { return NULL; }
+  if (ctx == NULL) {
+    return NULL;
+  }
 
   ctx->type = type;
   if (ctx->type == TFile) {
@@ -126,7 +128,9 @@ WriterCtx* writerCtxCreate(WriterType type, const char* path, bool readOnly, int
 
   return ctx;
 END:
-  if (ctx->type == TMemory) { taosMemoryFree(ctx->mem.buf); }
+  if (ctx->type == TMemory) {
+    taosMemoryFree(ctx->mem.buf);
+  }
   taosMemoryFree(ctx);
   return NULL;
 }
@@ -148,14 +152,18 @@ void writerCtxDestroy(WriterCtx* ctx, bool remove) {
       // stat(ctx->file.buf, &fstat);
       // indexError("write file size: %d", (int)(fstat.st_size));
     }
-    if (remove) { unlink(ctx->file.buf); }
+    if (remove) {
+      unlink(ctx->file.buf);
+    }
   }
   taosMemoryFree(ctx);
 }
 
 FstCountingWriter* fstCountingWriterCreate(void* wrt) {
   FstCountingWriter* cw = taosMemoryCalloc(1, sizeof(FstCountingWriter));
-  if (cw == NULL) { return NULL; }
+  if (cw == NULL) {
+    return NULL;
+  }
 
   cw->wrt = wrt;
   //(void *)(writerCtxCreate(TFile, readOnly));
@@ -169,7 +177,9 @@ void fstCountingWriterDestroy(FstCountingWriter* cw) {
 }
 
 int fstCountingWriterWrite(FstCountingWriter* write, uint8_t* buf, uint32_t len) {
-  if (write == NULL) { return 0; }
+  if (write == NULL) {
+    return 0;
+  }
   // update checksum
   // write data to file/socket or mem
   WriterCtx* ctx = write->wrt;
@@ -182,7 +192,9 @@ int fstCountingWriterWrite(FstCountingWriter* write, uint8_t* buf, uint32_t len)
   return len;
 }
 int fstCountingWriterRead(FstCountingWriter* write, uint8_t* buf, uint32_t len) {
-  if (write == NULL) { return 0; }
+  if (write == NULL) {
+    return 0;
+  }
   WriterCtx* ctx = write->wrt;
   int        nRead = ctx->read(ctx, buf, len);
   // assert(nRead == len);
diff --git a/source/libs/index/src/index_fst_node.c b/source/libs/index/src/indexFstNode.c
similarity index 89%
rename from source/libs/index/src/index_fst_node.c
rename to source/libs/index/src/indexFstNode.c
index a0d59150d7..e11f9dd37d 100644
--- a/source/libs/index/src/index_fst_node.c
+++ b/source/libs/index/src/indexFstNode.c
@@ -12,7 +12,7 @@
  * 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/>.
  */
-#include "index_fst_node.h"
+#include "indexFstNode.h"
 
 FstBuilderNode* fstBuilderNodeDefault() {
   FstBuilderNode* bn = taosMemoryMalloc(sizeof(FstBuilderNode));
@@ -22,31 +22,45 @@ FstBuilderNode* fstBuilderNodeDefault() {
   return bn;
 }
 void fstBuilderNodeDestroy(FstBuilderNode* node) {
-  if (node == NULL) { return; }
+  if (node == NULL) {
+    return;
+  }
 
   taosArrayDestroy(node->trans);
   taosMemoryFree(node);
 }
 
 bool fstBuilderNodeEqual(FstBuilderNode* n1, FstBuilderNode* n2) {
-  if (n1 == n2) { return true; }
-  if (n1 == NULL || n2 == NULL) { return false; }
+  if (n1 == n2) {
+    return true;
+  }
+  if (n1 == NULL || n2 == NULL) {
+    return false;
+  }
 
-  if (n1->isFinal != n2->isFinal || n1->finalOutput != n2->finalOutput) { return false; }
+  if (n1->isFinal != n2->isFinal || n1->finalOutput != n2->finalOutput) {
+    return false;
+  }
   size_t s1 = n1->trans ? taosArrayGetSize(n1->trans) : 0;
   size_t s2 = n2->trans ? taosArrayGetSize(n2->trans) : 0;
-  if (s1 != s2) { return false; }
+  if (s1 != s2) {
+    return false;
+  }
   for (size_t i = 0; i < s1; i++) {
     FstTransition* t1 = taosArrayGet(n1->trans, i);
     FstTransition* t2 = taosArrayGet(n2->trans, i);
-    if (t1->inp != t2->inp || t1->out != t2->out || t1->addr != t2->addr) { return false; }
+    if (t1->inp != t2->inp || t1->out != t2->out || t1->addr != t2->addr) {
+      return false;
+    }
   }
 
   return true;
 }
 FstBuilderNode* fstBuilderNodeClone(FstBuilderNode* src) {
   FstBuilderNode* node = taosMemoryMalloc(sizeof(FstBuilderNode));
-  if (node == NULL) { return NULL; }
+  if (node == NULL) {
+    return NULL;
+  }
 
   //
   size_t  sz = taosArrayGetSize(src->trans);
@@ -64,7 +78,9 @@ FstBuilderNode* fstBuilderNodeClone(FstBuilderNode* src) {
 }
 // not destroy src, User's bussiness
 void fstBuilderNodeCloneFrom(FstBuilderNode* dst, FstBuilderNode* src) {
-  if (dst == NULL || src == NULL) { return; }
+  if (dst == NULL || src == NULL) {
+    return;
+  }
 
   dst->isFinal = src->isFinal;
   dst->finalOutput = src->finalOutput;
diff --git a/source/libs/index/src/index_fst_registry.c b/source/libs/index/src/indexFstRegister.c
similarity index 93%
rename from source/libs/index/src/index_fst_registry.c
rename to source/libs/index/src/indexFstRegister.c
index 7b6b8df25f..34efee0d0d 100644
--- a/source/libs/index/src/index_fst_registry.c
+++ b/source/libs/index/src/indexFstRegister.c
@@ -13,8 +13,8 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "indexFstRegistry.h"
 #include "os.h"
-#include "index_fst_registry.h"
 
 uint64_t fstRegistryHash(FstRegistry* registry, FstBuilderNode* bNode) {
   // TODO(yihaoDeng): refactor later
@@ -35,7 +35,9 @@ uint64_t fstRegistryHash(FstRegistry* registry, FstBuilderNode* bNode) {
 }
 static void fstRegistryCellSwap(SArray* arr, uint32_t a, uint32_t b) {
   size_t sz = taosArrayGetSize(arr);
-  if (a >= sz || b >= sz) { return; }
+  if (a >= sz || b >= sz) {
+    return;
+  }
 
   FstRegistryCell* cell1 = (FstRegistryCell*)taosArrayGet(arr, a);
   FstRegistryCell* cell2 = (FstRegistryCell*)taosArrayGet(arr, b);
@@ -52,7 +54,9 @@ static void fstRegistryCellSwap(SArray* arr, uint32_t a, uint32_t b) {
 
 static void fstRegistryCellPromote(SArray* arr, uint32_t start, uint32_t end) {
   size_t sz = taosArrayGetSize(arr);
-  if (start >= sz && end >= sz) { return; }
+  if (start >= sz && end >= sz) {
+    return;
+  }
 
   assert(start >= end);
 
@@ -66,7 +70,9 @@ static void fstRegistryCellPromote(SArray* arr, uint32_t start, uint32_t end) {
 
 FstRegistry* fstRegistryCreate(uint64_t tableSize, uint64_t mruSize) {
   FstRegistry* registry = taosMemoryMalloc(sizeof(FstRegistry));
-  if (registry == NULL) { return NULL; }
+  if (registry == NULL) {
+    return NULL;
+  }
 
   uint64_t nCells = tableSize * mruSize;
   SArray*  tb = (SArray*)taosArrayInit(nCells, sizeof(FstRegistryCell));
@@ -87,7 +93,9 @@ FstRegistry* fstRegistryCreate(uint64_t tableSize, uint64_t mruSize) {
 }
 
 void fstRegistryDestroy(FstRegistry* registry) {
-  if (registry == NULL) { return; }
+  if (registry == NULL) {
+    return;
+  }
 
   SArray* tb = registry->table;
   size_t  sz = taosArrayGetSize(tb);
@@ -100,7 +108,9 @@ void fstRegistryDestroy(FstRegistry* registry) {
 }
 
 FstRegistryEntry* fstRegistryGetEntry(FstRegistry* registry, FstBuilderNode* bNode) {
-  if (taosArrayGetSize(registry->table) <= 0) { return NULL; }
+  if (taosArrayGetSize(registry->table) <= 0) {
+    return NULL;
+  }
   uint64_t bucket = fstRegistryHash(registry, bNode);
   uint64_t start = registry->mruSize * bucket;
   uint64_t end = start + registry->mruSize;
@@ -165,6 +175,4 @@ FstRegistryEntry* fstRegistryGetEntry(FstRegistry* registry, FstBuilderNode* bNo
   }
   return entry;
 }
-void fstRegistryEntryDestroy(FstRegistryEntry* entry) {
-  taosMemoryFree(entry);
-}
+void fstRegistryEntryDestroy(FstRegistryEntry* entry) { taosMemoryFree(entry); }
diff --git a/source/libs/index/src/index_fst_util.c b/source/libs/index/src/indexFstUtil.c
similarity index 98%
rename from source/libs/index/src/index_fst_util.c
rename to source/libs/index/src/indexFstUtil.c
index f9581f7202..ec9a6943dc 100644
--- a/source/libs/index/src/index_fst_util.c
+++ b/source/libs/index/src/indexFstUtil.c
@@ -12,8 +12,8 @@
  * 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/>.
  */
-#include "index_fst_util.h"
-#include "index_fst_common.h"
+#include "indexFstUtil.h"
+#include "indexFstCommon.h"
 
 // A sentinel value used to indicate an empty final state
 const CompiledAddr EMPTY_ADDRESS = 0;
diff --git a/source/libs/index/src/index_json.c b/source/libs/index/src/indexJson.c
similarity index 100%
rename from source/libs/index/src/index_json.c
rename to source/libs/index/src/indexJson.c
diff --git a/source/libs/index/src/indexSparse.c b/source/libs/index/src/indexSparse.c
new file mode 100644
index 0000000000..8bcf04602f
--- /dev/null
+++ b/source/libs/index/src/indexSparse.c
@@ -0,0 +1,71 @@
+/*
+ * 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/>.
+ */
+
+#include "indexSparse.h"
+
+FstSparseSet *sparSetCreate(int32_t sz) {
+  FstSparseSet *ss = taosMemoryCalloc(1, sizeof(FstSparseSet));
+  if (ss = NULL) {
+    return NULL;
+  }
+
+  ss->dense = taosArrayInit(sz, sizeof(uint32_t));
+  ss->sparse = taosArrayInit(sz, sizeof(uint32_t));
+  ss->size = sz;
+  return ss;
+}
+void sparSetDestroy(FstSparseSet *ss) {
+  if (ss == NULL) {
+    return;
+  }
+  taosArrayDestroy(ss->dense);
+  taosArrayDestroy(ss->sparse);
+  taosMemoryFree(ss);
+}
+uint32_t sparSetLen(FstSparseSet *ss) { return ss == NULL ? 0 : ss->size; }
+uint32_t sparSetAdd(FstSparseSet *ss, uint32_t ip) {
+  if (ss == NULL) {
+    return 0;
+  }
+  uint32_t i = ss->size;
+  taosArraySet(ss->dense, i, &ip);
+  taosArraySet(ss->sparse, ip, &i);
+  ss->size += 1;
+  return i;
+}
+uint32_t sparSetGet(FstSparseSet *ss, uint32_t i) {
+  if (i >= taosArrayGetSize(ss->dense)) {
+    return 0;
+  }
+  uint32_t *v = taosArrayGet(ss->dense, i);
+  return *v;
+}
+bool sparSetContains(FstSparseSet *ss, uint32_t ip) {
+  if (ip >= taosArrayGetSize(ss->sparse)) {
+    return false;
+  }
+  uint32_t i = *(uint32_t *)taosArrayGet(ss->sparse, ip);
+  if (i >= taosArrayGetSize(ss->dense)) {
+    return false;
+  }
+  uint32_t v = *(uint32_t *)taosArrayGet(ss->dense, i);
+  return v == ip;
+}
+void sparSetClear(FstSparseSet *ss) {
+  if (ss == NULL) {
+    return;
+  }
+  ss->size = 0;
+}
diff --git a/source/libs/index/src/index_tfile.c b/source/libs/index/src/indexTfile.c
similarity index 99%
rename from source/libs/index/src/index_tfile.c
rename to source/libs/index/src/indexTfile.c
index 53813e13e6..058c33b725 100644
--- a/source/libs/index/src/index_tfile.c
+++ b/source/libs/index/src/indexTfile.c
@@ -13,12 +13,12 @@ p *
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "index_tfile.h"
+#include "indexTfile.h"
 #include "index.h"
-#include "index_comm.h"
-#include "index_fst.h"
-#include "index_fst_counting_writer.h"
-#include "index_util.h"
+#include "indexComm.h"
+#include "indexFst.h"
+#include "indexFstCountingWriter.h"
+#include "indexUtil.h"
 #include "taosdef.h"
 #include "tcoding.h"
 #include "tcompare.h"
diff --git a/source/libs/index/src/index_util.c b/source/libs/index/src/indexUtil.c
similarity index 99%
rename from source/libs/index/src/index_util.c
rename to source/libs/index/src/indexUtil.c
index 65c16ca65b..7b83cf465d 100644
--- a/source/libs/index/src/index_util.c
+++ b/source/libs/index/src/indexUtil.c
@@ -12,7 +12,7 @@
  * 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/>.
  */
-#include "index_util.h"
+#include "indexUtil.h"
 #include "index.h"
 #include "tcompare.h"
 
diff --git a/source/libs/index/test/fstTest.cc b/source/libs/index/test/fstTest.cc
index e0b12a6f33..eff53108cd 100644
--- a/source/libs/index/test/fstTest.cc
+++ b/source/libs/index/test/fstTest.cc
@@ -5,12 +5,12 @@
 #include <thread>
 #include <vector>
 #include "index.h"
+#include "indexCache.h"
+#include "indexFst.h"
+#include "indexFstCountingWriter.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_cache.h"
-#include "index_fst.h"
-#include "index_fst_counting_writer.h"
-#include "index_fst_util.h"
-#include "index_tfile.h"
+#include "indexTfile.h"
 #include "tskiplist.h"
 #include "tutil.h"
 void* callback(void* s) { return s; }
diff --git a/source/libs/index/test/fstUT.cc b/source/libs/index/test/fstUT.cc
index e7efbaf21f..ab6c1a4704 100644
--- a/source/libs/index/test/fstUT.cc
+++ b/source/libs/index/test/fstUT.cc
@@ -6,12 +6,12 @@
 #include <thread>
 #include <vector>
 #include "index.h"
+#include "indexCache.h"
+#include "indexFst.h"
+#include "indexFstCountingWriter.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_cache.h"
-#include "index_fst.h"
-#include "index_fst_counting_writer.h"
-#include "index_fst_util.h"
-#include "index_tfile.h"
+#include "indexTfile.h"
 #include "tglobal.h"
 #include "tlog.h"
 #include "tskiplist.h"
diff --git a/source/libs/index/test/indexTests.cc b/source/libs/index/test/indexTests.cc
index 0e4eb060cf..ee9da50ab2 100644
--- a/source/libs/index/test/indexTests.cc
+++ b/source/libs/index/test/indexTests.cc
@@ -18,13 +18,13 @@
 #include <string>
 #include <thread>
 #include "index.h"
+#include "indexCache.h"
+#include "indexFst.h"
+#include "indexFstCountingWriter.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_cache.h"
-#include "index_fst.h"
-#include "index_fst_counting_writer.h"
-#include "index_fst_util.h"
-#include "index_tfile.h"
-#include "index_util.h"
+#include "indexTfile.h"
+#include "indexUtil.h"
 #include "tskiplist.h"
 #include "tutil.h"
 using namespace std;
diff --git a/source/libs/index/test/jsonUT.cc b/source/libs/index/test/jsonUT.cc
index df9f8b8439..9b0452425a 100644
--- a/source/libs/index/test/jsonUT.cc
+++ b/source/libs/index/test/jsonUT.cc
@@ -5,13 +5,13 @@
 #include <thread>
 #include <vector>
 #include "index.h"
+#include "indexCache.h"
+#include "indexFst.h"
+#include "indexFstCountingWriter.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_cache.h"
-#include "index_fst.h"
-#include "index_fst_counting_writer.h"
-#include "index_fst_util.h"
-#include "index_tfile.h"
-#include "index_util.h"
+#include "indexTfile.h"
+#include "indexUtil.h"
 #include "tglobal.h"
 #include "tskiplist.h"
 #include "tutil.h"
diff --git a/source/libs/index/test/utilUT.cc b/source/libs/index/test/utilUT.cc
index 6ba8cc9525..30f1a089f7 100644
--- a/source/libs/index/test/utilUT.cc
+++ b/source/libs/index/test/utilUT.cc
@@ -5,13 +5,13 @@
 #include <thread>
 #include <vector>
 #include "index.h"
+#include "indexCache.h"
+#include "indexFst.h"
+#include "indexFstCountingWriter.h"
+#include "indexFstUtil.h"
 #include "indexInt.h"
-#include "index_cache.h"
-#include "index_fst.h"
-#include "index_fst_counting_writer.h"
-#include "index_fst_util.h"
-#include "index_tfile.h"
-#include "index_util.h"
+#include "indexTfile.h"
+#include "indexUtil.h"
 #include "tglobal.h"
 #include "tskiplist.h"
 #include "tutil.h"