feat(driver-adapters): add "version()" support to QuaintQueryable

quaint/src/visitor.rs

@@ -68,11 +68,6 @@ pub trait Visitor<'a> {
     /// Write to the query.
     fn write<D: fmt::Display>(&mut self, s: D) -> Result;
 
-    /// Name of the function used to view the version of the database.
-    fn version_fn(&self) -> &'static str {
-        "version"
-    }
-
     /// A point to modify an incoming query to make it compatible with the
     /// underlying database.
     fn compatibility_modifications(&self, query: Query<'a>) -> Query<'a> {

quaint/src/visitor/mysql.rs

@@ -16,6 +16,11 @@ pub struct Mysql<'a> {
 }
 
 impl<'a> Mysql<'a> {
+    /// Name of the function used to view the version of the database.
+    pub const fn version_fn() -> &'static str {
+        "version"
+    }
+
     fn visit_regular_equality_comparison(&mut self, left: Expression<'a>, right: Expression<'a>) -> visitor::Result {
         self.visit_expression(left)?;
         self.write(" = ")?;

quaint/src/visitor/postgres.rs

@@ -18,6 +18,11 @@ pub struct Postgres<'a> {
 }
 
 impl<'a> Postgres<'a> {
+    /// Name of the function used to view the version of the database.
+    pub const fn version_fn() -> &'static str {
+        "version"
+    }
+
     fn visit_json_build_obj_expr(&mut self, expr: Expression<'a>) -> crate::Result<()> {
         match expr.kind() {
             ExpressionKind::Column(col) => match (col.type_family.as_ref(), col.native_type.as_deref()) {

quaint/src/visitor/sqlite.rs

@@ -16,6 +16,11 @@ pub struct Sqlite<'a> {
 }
 
 impl<'a> Sqlite<'a> {
+    /// Name of the function used to view the version of the database.
+    pub const fn version_fn() -> &'static str {
+        "sqlite_version"
+    }
+
     fn returning(&mut self, returning: Option<Vec<Column<'a>>>) -> visitor::Result {
         if let Some(returning) = returning {
             if !returning.is_empty() {
@@ -95,10 +100,6 @@ impl<'a> Visitor<'a> for Sqlite<'a> {
         Ok(())
     }
 
-    fn version_fn(&self) -> &'static str {
-        "sqlite_version"
-    }
-
     fn visit_raw_value(&mut self, value: Value<'a>) -> visitor::Result {
         let res = match &value.typed {
             ValueType::Int32(i) => i.map(|i| self.write(i)),