diff --git a/source/libs/tdb/src/db/btree.c b/source/libs/tdb/src/db/btree.c
index 2ce1e62c16..e87a25c2c3 100644
--- a/source/libs/tdb/src/db/btree.c
+++ b/source/libs/tdb/src/db/btree.c
@@ -13,4 +13,12 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "tdbInt.h"
\ No newline at end of file
+#include "tdbInt.h"
+
+struct SBTree {
+  // TODO
+};
+
+struct SBtCursor {
+  // TODO
+};
\ No newline at end of file
diff --git a/source/libs/tdb/src/db/pgcache.c b/source/libs/tdb/src/db/pgcache.c
index 2ce1e62c16..25ce90e772 100644
--- a/source/libs/tdb/src/db/pgcache.c
+++ b/source/libs/tdb/src/db/pgcache.c
@@ -13,4 +13,55 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "tdbInt.h"
\ No newline at end of file
+#include "tdbInt.h"
+
+struct SPage {
+  pgid_t pgid;  // page id
+  // TODO
+};
+
+typedef TD_DLIST(SPage) SPgList;
+
+struct SPgCache {
+  SPage *pages;
+
+  SPgList freeList;
+
+  struct {
+    int32_t nbucket;
+    struct {
+      SRWLatch latch;
+      TD_DLIST(SPage) ht;
+    } * buckets;
+  } pght;  // page hash table
+};
+
+int pgCacheCreate(SPgCache **ppPgCache) {
+  // TODO
+  return 0;
+}
+
+int pgCacheDestroy(SPgCache *pPgCache) {
+  // TODO
+  return 0;
+}
+
+int pgCacheOpen(SPgCache *pPgCache) {
+  // TODO
+  return 0;
+}
+
+int pgCacheClose(SPgCache *pPgCache) {
+  // TODO
+  return 0;
+}
+
+SPage *pgCacheFetch(SPgCache *pPgCache) {
+  // TODO
+  return NULL;
+}
+
+int pgCacheRelease(SPage *pPage) {
+  // TODO
+  return 0;
+}
\ No newline at end of file
diff --git a/source/libs/tdb/src/inc/btree.h b/source/libs/tdb/src/inc/btree.h
index 7b1b6cd2ef..757525d6a7 100644
--- a/source/libs/tdb/src/inc/btree.h
+++ b/source/libs/tdb/src/inc/btree.h
@@ -20,11 +20,8 @@
 extern "C" {
 #endif
 
-typedef struct SBTree SBTree;
-
-struct SBTree {
-  // TODO
-};
+typedef struct SBTree    SBTree;
+typedef struct SBtCursor SBtCursor;
 
 #ifdef __cplusplus
 }
diff --git a/source/libs/tdb/src/inc/pgcache.h b/source/libs/tdb/src/inc/pgcache.h
index 0bf5d22f3f..af85e0de63 100644
--- a/source/libs/tdb/src/inc/pgcache.h
+++ b/source/libs/tdb/src/inc/pgcache.h
@@ -34,11 +34,6 @@ int    pgCacheRelease(SPage *pPage);
 
 // SPage
 
-// Impl
-struct SPgCache {
-  // TODO
-};
-
 #ifdef __cplusplus
 }
 #endif