feat(mysql): expand MySqlColumn, add various helper methods

sqlx-mysql/src/column.rs

@@ -1,23 +1,68 @@
 use bytestring::ByteString;
 use sqlx_core::Column;
 
+use crate::protocol::{ColumnDefinition, ColumnFlags};
+use crate::{MySql, MySqlTypeInfo};
+
+/// Represents a column from a query in MySQL.
 #[allow(clippy::module_name_repetitions)]
+#[derive(Debug, Clone)]
 pub struct MySqlColumn {
     ordinal: usize,
     name: ByteString,
+    type_info: MySqlTypeInfo,
+    flags: ColumnFlags,
 }
 
 impl MySqlColumn {
+    pub(crate) fn new(ordinal: usize, def: ColumnDefinition) -> Self {
+        Self { type_info: MySqlTypeInfo::new(&def), ordinal, name: def.name, flags: def.flags }
+    }
+}
+
+impl MySqlColumn {
+    /// Returns the name of the column.
+    ///
+    /// If the original name of the column has been aliased, this will return
+    /// the aliased name.
+    ///
     pub fn name(&self) -> &str {
         &self.name
     }
 
+    /// Returns type information of the column.
+    pub fn type_info(&self) -> &MySqlTypeInfo {
+        &self.type_info
+    }
+
+    /// Returns the (zero-based) position of the column.
     pub const fn ordinal(&self) -> usize {
         self.ordinal
     }
+
+    /// Returns `true` if the column is (or is part of) a `PRIMARY KEY`.
+    pub const fn is_primary_key(&self) -> bool {
+        self.flags.contains(ColumnFlags::PRIMARY_KEY)
+    }
+
+    /// Returns `true` if the column is nullable.
+    pub const fn is_nullable(&self) -> bool {
+        !self.flags.contains(ColumnFlags::NOT_NULL)
+    }
+
+    /// Returns `true` if the column is has a default value.
+    ///
+    /// Always returns `true` if the column is nullable as `NULL` is
+    /// a valid default value.
+    ///
+    pub const fn has_default_value(&self) -> bool {
+        !self.flags.contains(ColumnFlags::NO_DEFAULT_VALUE)
+    }
 }
 
 impl Column for MySqlColumn {
+    type Database = MySql;
+
     #[inline]
     fn name(&self) -> &str {
         self.name()
@@ -27,4 +72,9 @@ impl Column for MySqlColumn {
     fn ordinal(&self) -> usize {
         self.ordinal()
     }
+
+    #[inline]
+    fn type_info(&self) -> &MySqlTypeInfo {
+        self.type_info()
+    }
 }