diff --git a/.github/workflows/function-comparison.yml b/.github/workflows/function-comparison.yml
new file mode 100644
index 0000000..405c563
--- /dev/null
+++ b/.github/workflows/function-comparison.yml
@@ -0,0 +1,34 @@
+# Copyright 2023 Greptime Team
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+name: Function Comparison
+
+on:
+  schedule:
+    - cron: '0 0 * * 0'
+  workflow_dispatch:
+
+jobs:
+  compare:
+    name: Compare Functions
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.x'
+      - name: Run function comparison
+        run: python scripts/compare_functions.py
diff --git a/scripts/compare_functions.py b/scripts/compare_functions.py
new file mode 100755
index 0000000..4652320
--- /dev/null
+++ b/scripts/compare_functions.py
@@ -0,0 +1,277 @@
+#!/usr/bin/env python3
+"""
+Script to compare Prometheus Go functions.go with Rust functions.rs
+Ensures Rust functions are complete and consistent with Go version.
+"""
+
+import re
+import sys
+from typing import Dict, List, Optional, Tuple
+from dataclasses import dataclass
+
+
+@dataclass
+class FunctionDef:
+    name: str
+    arg_types: List[str]
+    variadic: int
+    return_type: str
+    experimental: bool
+
+    def __str__(self):
+        exp_flag = " [EXP]" if self.experimental else ""
+        return f"{self.name}: args={self.arg_types}, variadic={self.variadic}, return={self.return_type}{exp_flag}"
+
+
+def parse_go_functions(content: str) -> Dict[str, FunctionDef]:
+    """Parse Prometheus Go functions.go to extract function definitions."""
+    functions = {}
+
+    # Find all function entry points
+    entries = []
+    pattern = r'"([^"]+)":\s*\{'
+    for match in re.finditer(pattern, content):
+        entries.append((match.start(), match.end(), match.group(1)))
+
+    # Extract each function block
+    for i, (start, end, name) in enumerate(entries):
+        block_start = end
+        # Find the closing brace for this block
+        brace_count = 1
+        block_end = block_start
+        while brace_count > 0 and block_end < len(content):
+            block_end += 1
+            if content[block_end] == "{":
+                brace_count += 1
+            elif content[block_end] == "}":
+                brace_count -= 1
+
+        block_content = content[block_start:block_end]
+
+        # Parse Name field
+        name_match = re.search(r'Name:\s*"([^"]+)"', block_content)
+        if not name_match:
+            continue
+
+        # Parse ArgTypes field
+        arg_types = []
+        arg_types_match = re.search(
+            r"ArgTypes:\s*\[\]ValueType\{(.*?)\}", block_content, re.DOTALL
+        )
+        if arg_types_match:
+            arg_types_str = arg_types_match.group(1).strip()
+            for arg in re.findall(r"ValueType(\w+)", arg_types_str):
+                arg_types.append(arg)
+
+        # Parse Variadic field
+        variadic = 0
+        variadic_match = re.search(r"Variadic:\s*(-?\d+)", block_content)
+        if variadic_match:
+            variadic = int(variadic_match.group(1))
+
+        # Parse ReturnType field
+        return_type = ""
+        return_match = re.search(r"ReturnType:\s*([^,\n}]+)", block_content)
+        if return_match:
+            return_type_clean = re.sub(r"ValueType", "", return_match.group(1)).strip()
+            return_type = return_type_clean
+
+        # Parse Experimental field
+        experimental = False
+        experimental_match = re.search(r"Experimental:\s*(true|false)", block_content)
+        if experimental_match:
+            experimental = experimental_match.group(1).lower() == "true"
+
+        functions[name] = FunctionDef(
+            name=name,
+            arg_types=arg_types,
+            variadic=variadic,
+            return_type=return_type,
+            experimental=experimental,
+        )
+
+    return functions
+
+
+def parse_rust_functions(content: str) -> Dict[str, FunctionDef]:
+    """Parse Rust functions.rs to extract function definitions."""
+    functions = {}
+
+    # Pattern to match function! macro calls
+    # Example:
+    # function!("abs", vec![ValueType::Vector], 0, ValueType::Vector, false),
+    # function!("days_in_month", vec![ValueType::Vector], 1, ValueType::Vector, false),
+    # function!("label_join", vec![ValueType::Vector, ValueType::String, ValueType::String, ValueType::String], -1, ValueType::Vector, false),
+    # function!("double_exponential_smoothing", vec![ValueType::Matrix, ValueType::Scalar, ValueType::Scalar], 0, ValueType::Vector, true),
+    pattern = r'function!\(\s*"([^"]+)"\s*,\s*vec!\[(.*?)\]\s*,\s*(-?\d+)\s*,\s*ValueType::(\w+)\s*,\s*(true|false)\s*\),'
+
+    for match in re.finditer(pattern, content, re.DOTALL):
+        name = match.group(1)
+        arg_types_str = match.group(2).strip()
+        variadic = int(match.group(3))
+        return_type = match.group(4)
+        experimental = match.group(5).lower() == "true"
+
+        # Parse arg types
+        arg_types = []
+        if arg_types_str:
+            for arg in re.findall(r"ValueType::(\w+)", arg_types_str):
+                arg_types.append(arg)
+
+        functions[name] = FunctionDef(
+            name=name,
+            arg_types=arg_types,
+            variadic=variadic,
+            return_type=return_type,
+            experimental=experimental,
+        )
+
+    return functions
+
+
+def normalize_type(type_str: str) -> str:
+    """Normalize type names for comparison."""
+    # Map Go types to Rust types
+    type_mapping = {
+        "String": "String",
+        "None": "None",
+    }
+    return type_mapping.get(type_str, type_str)
+
+
+def compare_functions(go_func: FunctionDef, rust_func: FunctionDef) -> List[str]:
+    """Compare two function definitions and return list of differences."""
+    differences = []
+
+    # Compare arg types
+    go_args = [normalize_type(t) for t in go_func.arg_types]
+    rust_args = [normalize_type(t) for t in rust_func.arg_types]
+
+    if go_args != rust_args:
+        differences.append(f"  Arg types differ: Go={go_args}, Rust={rust_args}")
+
+    # Compare variadic
+    if go_func.variadic != rust_func.variadic:
+        differences.append(
+            f"  Variadic differs: Go={go_func.variadic}, Rust={rust_func.variadic}"
+        )
+
+    # Compare return type
+    go_return = normalize_type(go_func.return_type)
+    rust_return = normalize_type(rust_func.return_type)
+    if go_return != rust_return:
+        differences.append(f"  Return type differs: Go={go_return}, Rust={rust_return}")
+
+    # Compare experimental flag
+    if go_func.experimental != rust_func.experimental:
+        differences.append(
+            f"  Experimental flag differs: Go={go_func.experimental}, Rust={rust_func.experimental}"
+        )
+
+    return differences
+
+
+def main():
+    import subprocess
+
+    # Fetch Prometheus Go functions.go from GitHub
+    go_url = "https://raw.githubusercontent.com/prometheus/prometheus/main/promql/parser/functions.go"
+    print(f"Fetching Prometheus functions.go from {go_url}...")
+
+    try:
+        result = subprocess.run(
+            ["curl", "-s", go_url], capture_output=True, text=True, check=True
+        )
+        go_content = result.stdout
+    except Exception as e:
+        print(f"Error fetching Go file: {e}")
+        sys.exit(1)
+
+    # Read Rust functions.rs
+    rust_file = "src/parser/function.rs"
+    print(f"Reading Rust functions from {rust_file}...")
+
+    try:
+        with open(rust_file, "r") as f:
+            rust_content = f.read()
+    except Exception as e:
+        print(f"Error reading Rust file: {e}")
+        sys.exit(1)
+
+    # Parse both files
+    go_functions = parse_go_functions(go_content)
+    rust_functions = parse_rust_functions(rust_content)
+
+    print(f"\nParsed {len(go_functions)} functions from Go")
+    print(f"Parsed {len(rust_functions)} functions from Rust\n")
+
+    # Find missing functions in Rust
+    missing_in_rust = set(go_functions.keys()) - set(rust_functions.keys())
+
+    # Find extra functions in Rust
+    extra_in_rust = set(rust_functions.keys()) - set(go_functions.keys())
+
+    # Find differences in common functions
+    common_functions = set(go_functions.keys()) & set(rust_functions.keys())
+    differences = {}
+
+    for func_name in sorted(common_functions):
+        go_func = go_functions[func_name]
+        rust_func = rust_functions[func_name]
+
+        diff = compare_functions(go_func, rust_func)
+        if diff:
+            differences[func_name] = (go_func, rust_func, diff)
+
+    # Print results
+    print("=" * 80)
+    print("COMPARISON RESULTS")
+    print("=" * 80)
+
+    if missing_in_rust:
+        print(f"\n❌ {len(missing_in_rust)} function(s) MISSING in Rust:")
+        for func in sorted(missing_in_rust):
+            print(f"  - {func}")
+
+    if extra_in_rust:
+        print(f"\n⚠️  {len(extra_in_rust)} function(s) EXTRA in Rust (not in Go):")
+        for func in sorted(extra_in_rust):
+            print(f"  - {func}")
+
+    if differences:
+        print(f"\n🔍 {len(differences)} function(s) have DIFFERENCES:")
+        for func_name in sorted(differences.keys()):
+            go_func, rust_func, diff = differences[func_name]
+            print(f"\n  {func_name}:")
+            print(f"    Go version:   {go_func}")
+            print(f"    Rust version: {rust_func}")
+            for d in diff:
+                print(f"    {d}")
+
+    # Summary
+    print("\n" + "=" * 80)
+    print("SUMMARY")
+    print("=" * 80)
+
+    total_go = len(go_functions)
+    total_rust = len(rust_functions)
+    total_common = len(common_functions)
+    total_differences = len(differences)
+
+    print(f"Go functions:     {total_go}")
+    print(f"Rust functions:   {total_rust}")
+    print(f"Common functions: {total_common}")
+    print(f"Missing in Rust:  {len(missing_in_rust)}")
+    print(f"Extra in Rust:    {len(extra_in_rust)}")
+    print(f"Differences:      {total_differences}")
+
+    if not missing_in_rust and not differences:
+        print("\n✅ All functions are COMPLETE and CONSISTENT!")
+        sys.exit(0)
+    else:
+        print("\n❌ Issues found - please review and fix")
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/parser/ast.rs b/src/parser/ast.rs
index 8b1a296..078c724 100644
--- a/src/parser/ast.rs
+++ b/src/parser/ast.rs
@@ -1570,14 +1570,8 @@ fn check_ast_for_call(ex: Call) -> Result<Expr, String> {
             ));
         }
     } else {
-        let expected_args_len_without_default = expected_args_len.saturating_sub(1);
-        if expected_args_len_without_default > actual_args_len {
-            return Err(format!(
-                "expected at least {expected_args_len_without_default} argument(s) in call to '{name}', got {actual_args_len}"
-            ));
-        }
-
         if ex.func.variadic > 0 {
+            let expected_args_len_without_default = expected_args_len.saturating_sub(1);
             let expected_max_args_len =
                 expected_args_len_without_default + ex.func.variadic as usize;
             if expected_max_args_len < actual_args_len {
@@ -1585,6 +1579,10 @@ fn check_ast_for_call(ex: Call) -> Result<Expr, String> {
                     "expected at most {expected_max_args_len} argument(s) in call to '{name}', got {actual_args_len}"
                 ));
             }
+        } else if ex.func.variadic == -1 && expected_args_len > actual_args_len {
+            return Err(format!(
+                    "expected at least {expected_args_len} argument(s) in call to '{name}', got {actual_args_len}"
+                ));
         }
     }
 
diff --git a/src/parser/function.rs b/src/parser/function.rs
index b61a4be..78817ba 100644
--- a/src/parser/function.rs
+++ b/src/parser/function.rs
@@ -249,28 +249,28 @@ lazy_static! {
         ),
         function!("exp", vec![ValueType::Vector], 0, ValueType::Vector, false),
         function!(
-            "floor",
-            vec![ValueType::Vector],
+            "first_over_time",
+            vec![ValueType::Matrix],
             0,
             ValueType::Vector,
-            false
+            true
         ),
         function!(
-            "histogram_count",
+            "floor",
             vec![ValueType::Vector],
             0,
             ValueType::Vector,
             false
         ),
         function!(
-            "histogram_sum",
+            "histogram_avg",
             vec![ValueType::Vector],
             0,
             ValueType::Vector,
             false
         ),
         function!(
-            "histogram_avg",
+            "histogram_count",
             vec![ValueType::Vector],
             0,
             ValueType::Vector,
@@ -290,6 +290,18 @@ lazy_static! {
             ValueType::Vector,
             false
         ),
+        function!(
+            "histogram_quantiles",
+            vec![
+                ValueType::Vector,
+                ValueType::String,
+                ValueType::Scalar,
+                ValueType::Scalar
+            ],
+            9,
+            ValueType::Vector,
+            true
+        ),
         function!(
             "histogram_stddev",
             vec![ValueType::Vector],
@@ -304,6 +316,20 @@ lazy_static! {
             ValueType::Vector,
             false
         ),
+        function!(
+            "histogram_sum",
+            vec![ValueType::Vector],
+            0,
+            ValueType::Vector,
+            false
+        ),
+        function!(
+            "info",
+            vec![ValueType::Vector, ValueType::Vector],
+            1,
+            ValueType::Vector,
+            true
+        ),
         function!(
             "double_exponential_smoothing",
             vec![ValueType::Matrix, ValueType::Scalar, ValueType::Scalar],
@@ -381,6 +407,13 @@ lazy_static! {
             false
         ),
         function!("log2", vec![ValueType::Vector], 0, ValueType::Vector, false),
+        function!(
+            "mad_over_time",
+            vec![ValueType::Matrix],
+            0,
+            ValueType::Vector,
+            true
+        ),
         function!(
             "max_over_time",
             vec![ValueType::Matrix],
@@ -395,6 +428,34 @@ lazy_static! {
             ValueType::Vector,
             false
         ),
+        function!(
+            "ts_of_first_over_time",
+            vec![ValueType::Matrix],
+            0,
+            ValueType::Vector,
+            true
+        ),
+        function!(
+            "ts_of_last_over_time",
+            vec![ValueType::Matrix],
+            0,
+            ValueType::Vector,
+            true
+        ),
+        function!(
+            "ts_of_max_over_time",
+            vec![ValueType::Matrix],
+            0,
+            ValueType::Vector,
+            true
+        ),
+        function!(
+            "ts_of_min_over_time",
+            vec![ValueType::Matrix],
+            0,
+            ValueType::Vector,
+            true
+        ),
         function!(
             "minute",
             vec![ValueType::Vector],
@@ -467,14 +528,14 @@ lazy_static! {
         ),
         function!(
             "sort_by_label",
-            vec![ValueType::Vector, ValueType::String, ValueType::String],
+            vec![ValueType::Vector, ValueType::String],
             -1,
             ValueType::Vector,
             true
         ),
         function!(
             "sort_by_label_desc",
-            vec![ValueType::Vector, ValueType::String, ValueType::String],
+            vec![ValueType::Vector, ValueType::String],
             -1,
             ValueType::Vector,
             true
diff --git a/src/parser/parse.rs b/src/parser/parse.rs
index ed6dfd6..d852e11 100644
--- a/src/parser/parse.rs
+++ b/src/parser/parse.rs
@@ -1850,7 +1850,7 @@ mod tests {
             ("exp()", "expected 1 argument(s) in call to 'exp', got 0"),
             (
                 "label_join()",
-                "expected at least 3 argument(s) in call to 'label_join', got 0",
+                "expected at least 4 argument(s) in call to 'label_join', got 0",
             ),
             (
                 "sort_by_label()",