refactor: implement version as built-in function and use fixed mysql version (#3133)

* refactor:  implement version as built-in function

* test: add sqlness test for version()

src/common/function/src/system.rs

@@ -13,10 +13,12 @@
 // limitations under the License.
 
 pub mod build;
+pub mod version;
 
 use std::sync::Arc;
 
 use build::BuildFunction;
+use version::VersionFunction;
 
 use crate::function_registry::FunctionRegistry;
 
@@ -25,5 +27,6 @@ pub(crate) struct SystemFunction;
 impl SystemFunction {
     pub fn register(registry: &FunctionRegistry) {
         registry.register(Arc::new(BuildFunction));
+        registry.register(Arc::new(VersionFunction));
     }
 }

src/common/function/src/system/version.rs

@@ -0,0 +1,54 @@
+// 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.
+
+use std::sync::Arc;
+use std::{env, fmt};
+
+use common_query::error::Result;
+use common_query::prelude::{Signature, Volatility};
+use datatypes::data_type::ConcreteDataType;
+use datatypes::vectors::{StringVector, VectorRef};
+
+use crate::function::{Function, FunctionContext};
+
+#[derive(Clone, Debug, Default)]
+pub(crate) struct VersionFunction;
+
+impl fmt::Display for VersionFunction {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "VERSION")
+    }
+}
+
+impl Function for VersionFunction {
+    fn name(&self) -> &str {
+        "version"
+    }
+
+    fn return_type(&self, _input_types: &[ConcreteDataType]) -> Result<ConcreteDataType> {
+        Ok(ConcreteDataType::string_datatype())
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::exact(vec![], Volatility::Immutable)
+    }
+
+    fn eval(&self, _func_ctx: FunctionContext, _columns: &[VectorRef]) -> Result<VectorRef> {
+        let result = StringVector::from(vec![format!(
+            "5.7.20-greptimedb-{}",
+            env!("CARGO_PKG_VERSION")
+        )]);
+        Ok(Arc::new(result))
+    }
+}