diff --git a/cases/query/feature_signature_query.yaml b/cases/query/feature_signature_query.yaml
index 1cfbd9b229a..c0763d320e7 100644
--- a/cases/query/feature_signature_query.yaml
+++ b/cases/query/feature_signature_query.yaml
@@ -43,7 +43,7 @@ cases:
     mode: procedure-unsupport
     db: db1
     sql: |
-      select gcformat(
+      select concat("#", gcformat(
           discrete(3, -1),
           discrete(3, 0),
           discrete(3, int("null")),
@@ -57,31 +57,31 @@ cases:
           discrete(-1, 5),
           discrete(-2, 5),
           discrete(-3, 5),
-          discrete(-4, 5)) as instance,
+          discrete(-4, 5))) as instance;
     expect:
       schema: instance:string
       data: |
-        | 4:628 5:491882390849628 6:0 7:4 8:1 9:3 10:1 11:1 12:0 13:0 14:4
+        # | 4:628 5:491882390849628 6:0 7:4 8:1 9:3 10:1 11:1 12:0 13:0 14:4
   - id: 2
     desc: feature signature select GCFormat no label
     mode: procedure-unsupport
     db: db1
     sql: |
-      select gcformat(
+      select concat("#", gcformat(
           discrete(hash64("x"), 1),
           continuous(pow(10, 30)),
           continuous(-pow(10, 1000)),
-          continuous(abs(sqrt(-1)))) as instance;
+          continuous(abs(sqrt(-1))))) as instance;
     expect:
       schema: instance:string
       data: |
-        | 1:0 2:0:1000000000000000019884624838656.000000 3:0:-inf 4:0:nan
+        # | 1:0 2:3353244675891348105:1000000000000000019884624838656.000000 3:7262150054277104024:-inf 4:3255232038643208583:nan
   - id: 3
     desc: feature signature GCFormat null
     mode: procedure-unsupport
     db: db1
     sql: |
-      select gcformat(
+      select concat("#", gcformat(
           regression_label(2),
           regression_label(int("null")),
           continuous(int("null")),
@@ -98,31 +98,31 @@ cases:
           discrete(3, -100),
           discrete(3),
           continuous(0.0),
-          continuous(int("null"))) as instance;
+          continuous(int("null")))) as instance;
     expect:
       schema: instance:string
       data: |
-        | 3:0:-1 4:0:2681491882390849628 5:28 8:2681491882390849628 9:0:-1 10:28 13:2681491882390849628 14:0:0.000000
+        # | 3:7262150054277104024:-1 4:3255232038643208583:2681491882390849628 5:28 8:2681491882390849628 9:-7745589761753622095:-1 10:28 13:2681491882390849628 14:398281081943027035:0.000000
   - id: 4
     desc: feature signature GCFormat no feature
     mode: procedure-unsupport
     db: db1
     sql: |
-      select gcformat(binary_label(false));
+      select concat(gcformat(binary_label(false)), "#") as instance;
     expect:
-      schema: gcformat(binary_label(false)):string
+      schema: instance:string
       data: |
-        0|
+        0 | #
   - id: 5
     desc: feature signature GCFormat nothing
     mode: procedure-unsupport
     db: db1
     sql: |
-      select gcformat();
+      select concat(concat("#", gcformat()), "#") as instance;
     expect:
-      schema: gcformat():string
+      schema: instance:string
       data: |
-        |
+        # | #
   - id: 6
     desc: feature signature CSV no label
     mode: procedure-unsupport
@@ -136,7 +136,7 @@ cases:
     expect:
       columns: [instance:string]
       rows:
-        - [",,,628"]
+        - [ ",,,628" ]
   - id: 7
     desc: feature signature CSV null
     mode: procedure-unsupport
@@ -163,7 +163,7 @@ cases:
     expect:
       columns: [ "instance:string "]
       rows:
-        - ["2,,,,-1,2681491882390849628,28,,,2681491882390849628,-1,28,,,2681491882390849628,0.000000,"]
+        - [ "2,,,,-1,2681491882390849628,28,,,2681491882390849628,-1,28,,,2681491882390849628,0.000000," ]
   - id: 8
     desc: feature signature CSV no feature
     mode: procedure-unsupport
@@ -263,7 +263,7 @@ cases:
     expect:
       schema: instance:string
       data: |
-        1| 1:0:0 2:0:1 3:0
+        1 | 1:5925585971146611297:0 2:3353244675891348105:1 3:0
   - id: 15
     desc: feature signature select GCFormat from
     mode: request-unsupport
@@ -289,11 +289,11 @@ cases:
       schema: instance:string
       order: instance
       data: |
-        1| 1:0:0 2:0:1 3:0
-        2| 1:0:0 2:0:2 3:0
-        3| 1:0:1 2:0:3 3:0
-        4| 1:0:1 2:0:4 3:0
-        5| 1:0:2 2:0:5 3:0
+        1 | 1:5925585971146611297:0 2:3353244675891348105:1 3:0
+        2 | 1:5925585971146611297:0 2:3353244675891348105:2 3:0
+        3 | 1:5925585971146611297:1 2:3353244675891348105:3 3:0
+        4 | 1:5925585971146611297:1 2:3353244675891348105:4 3:0
+        5 | 1:5925585971146611297:2 2:3353244675891348105:5 3:0
   - id: 16
     desc: feature signature select CSV from
     mode: request-unsupport
@@ -360,7 +360,7 @@ cases:
     mode: request-unsupport
     db: db1
     sql: |
-      SELECT gcformat(regression_label(col1)) as col1,
+      SELECT gcformat(regression_label(col1), discrete(col1, 1)) as col1,
           csv(regression_label(col1)) as col2,
           libsvm(regression_label(col1)) as col3
       FROM t1;
@@ -375,14 +375,14 @@ cases:
           1, 4, 55, 4.4, 44.4, 2, 4444
           2, 5, 55, 5.5, 55.5, 3, aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     expect:
-      schema: col1:string, col2:string, col3:string
-      order: col1
-      data: |
-        1|, 1, 1
-        2|, 2, 2
-        3|, 3, 3
-        4|, 4, 4
-        5|, 5, 5
+      columns: [ "col1:string", "col2:string", "col3:string" ]
+      order: "col1"
+      rows:
+        - [ "1 | 1:0", "1", "1" ]
+        - [ "2 | 1:0", "2", "2" ]
+        - [ "3 | 1:0", "3", "3" ]
+        - [ "4 | 1:0", "4", "4" ]
+        - [ "5 | 1:0", "5", "5" ]
   - id: 19
     desc: feature signature select from join
     mode: request-unsupport
@@ -471,15 +471,25 @@ cases:
     mode: procedure-unsupport
     db: db1
     sql: |
-      select gcformat(
+      select concat("#", gcformat(
           regression_label(2),
           continuous(1),
           continuous(int("notint")),
           continuous(0),
           continuous(0.0),
           discrete(3),
-          regression_label(int("notint"))) as instance;
+          regression_label(int("notint")))) as instance;
     expect:
       schema: instance:string
       data: |
-        | 1:0:1 3:0:0 4:0:0.000000 5:2681491882390849628
+        # | 1:5925585971146611297:1 3:7262150054277104024:0 4:3255232038643208583:0.000000 5:2681491882390849628
+  - id: 23
+    desc: hash64
+    mode: procedure-unsupport
+    db: db1
+    sql: |
+      select hash64(3) as col1, hash64(bigint(3)) as col2;
+    expect:
+      schema: col1:int64, col2:int64
+      data: |
+        2681491882390849628, 7262150054277104024
diff --git a/hybridse/src/udf/default_defs/feature_signature_def.cc b/hybridse/src/udf/default_defs/feature_signature_def.cc
index 3f9586c7f61..b407d513bb4 100644
--- a/hybridse/src/udf/default_defs/feature_signature_def.cc
+++ b/hybridse/src/udf/default_defs/feature_signature_def.cc
@@ -204,14 +204,23 @@ struct GCFormat {
         switch (feature_signature) {
             case kFeatureSignatureContinuous: {
                 if (!is_null) {
-                    instance_feature += " " + std::to_string(slot_number) + ":0:" + format_continuous(input);
+                    if (!instance_feature.empty()) {
+                        instance_feature += " ";
+                    }
+                    int64_t hash = FarmFingerprint(CCallDataTypeTrait<int64_t>::to_bytes_ref(&slot_number));
+                    instance_feature += std::to_string(slot_number) + ":";
+                    instance_feature += format_discrete(hash);
+                    instance_feature += ":" + format_continuous(input);
                 }
                 ++slot_number;
                 break;
             }
             case kFeatureSignatureDiscrete: {
                 if (!is_null) {
-                    instance_feature += " " + std::to_string(slot_number) + ":" + format_discrete(input);
+                    if (!instance_feature.empty()) {
+                        instance_feature += " ";
+                    }
+                    instance_feature += std::to_string(slot_number) + ":" + format_discrete(input);
                 }
                 ++slot_number;
                 break;
@@ -249,7 +258,7 @@ struct GCFormat {
     }
 
     std::string Output() {
-        return instance_label + "|" + instance_feature;
+        return instance_label + " | " + instance_feature;
     }
 
     size_t slot_number = 1;
@@ -482,7 +491,7 @@ void DefaultUdfLibrary::InitFeatureSignature() {
              Example:
              @code{.sql}
                 select gcformat(multiclass_label(6), continuous(1.5), category(3));
-                -- output 6| 1:0:1.500000 2:2681491882390849628
+                -- output 6 | 1:0:1.500000 2:2681491882390849628
              @endcode
 
              @since 0.9.0