Adjust MySQL ColumnDefinitions

This commits aims to make Readyset ColumnDefinition package more
aligned with MySQL's ColumnDefinition package.

The main changes are:
- Add `decimals` to the `Column` struct.
- Made `column_length` non optional. Before we were always returning
it to 1024. Now we have proper lenght based on field type.
- Adjusted most of the Flags to match MySQL.
- Added `sql_type` to `ColumnBase`. Some DfTypes don't record the
precision, like all sql text fields (TinyText, MediumText, LongText)
translate to DfType::Text, they all have a different length. MySQL
Boolean come as tinyint(1) during snapshot, but Boolean during
replication.

Added an integration test to validate we are returning same
column definitions for both upstream MySQL and Readyset.

Closes: REA-4505
Closes: #1321

Release-Note-Core: Adjust MySQL ColumnDefinitions to match MySQL.
  Some drivers, like ruby-mysql2, use the column definition to round
  decimal numbers.

Change-Id: I1a2c2e7fe5915b32d9f96cb600c408c6b20c874b
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/9075
Tested-by: Buildkite CI
Reviewed-by: Michael Zink <michael.z@readyset.io>

Author: altmannmarcelo

mysql-srv/src/lib.rs

@@ -82,9 +82,10 @@
 //!                         table: String::new(),
 //!                         column: "@@max_allowed_packet".to_owned(),
 //!                         coltype: myc::constants::ColumnType::MYSQL_TYPE_LONG,
-//!                         column_length: None,
+//!                         column_length: 11,
 //!                         colflags: myc::constants::ColumnFlags::UNSIGNED_FLAG,
 //!                         character_set: myc::constants::UTF8_GENERAL_CI,
+//!                         decimals: 0,
 //!                     }];
 //!                     let mut w = results.start(cols).await.expect("cols");
 //!                     w.write_row(iter::once(67108864u32)).await.expect("writer");
@@ -98,17 +99,19 @@
 //!                     table: "foo".to_string(),
 //!                     column: "a".to_string(),
 //!                     coltype: ColumnType::MYSQL_TYPE_LONGLONG,
-//!                     column_length: None,
+//!                     column_length: 11,
 //!                     colflags: ColumnFlags::empty(),
 //!                     character_set: myc::constants::UTF8_GENERAL_CI,
+//!                     decimals: 0,
 //!                 },
 //!                 Column {
 //!                     table: "foo".to_string(),
 //!                     column: "b".to_string(),
 //!                     coltype: ColumnType::MYSQL_TYPE_STRING,
-//!                     column_length: None,
+//!                     column_length: 11,
 //!                     colflags: ColumnFlags::empty(),
 //!                     character_set: myc::constants::UTF8_GENERAL_CI,
+//!                     decimals: 0,
 //!                 },
 //!             ];
 //!
@@ -226,13 +229,16 @@ pub struct Column {
     /// This column's type.
     pub coltype: ColumnType,
     /// This column's display length.
-    pub column_length: Option<u32>,
+    pub column_length: u32,
     /// Holds the character set for this column.
     pub character_set: u16,
     /// Any flags associated with this column.
     ///
     /// Of particular interest are [`ColumnFlags::UNSIGNED_FLAG`] and [`ColumnFlags::NOT_NULL_FLAG`]
     pub colflags: ColumnFlags,
+
+    /// Column Decimal Precision
+    pub decimals: u8,
 }
 
 impl From<&mysql_async::Column> for Column {
@@ -241,9 +247,10 @@ impl From<&mysql_async::Column> for Column {
             table: c.table_str().to_string(),
             column: c.name_str().to_string(),
             coltype: c.column_type(),
-            column_length: Some(c.column_length()),
+            column_length: c.column_length(),
             character_set: c.character_set(),
             colflags: c.flags(),
+            decimals: c.decimals(),
         }
     }
 }

mysql-srv/src/value/decode.rs

@@ -359,9 +359,10 @@ mod tests {
                     table: String::new(),
                     column: String::new(),
                     coltype: $ct,
-                    column_length: None,
+                    column_length: 0,
                     colflags: ColumnFlags::empty(),
                     character_set: 33,
+                    decimals: 0,
                 };
 
                 if !$sig {

mysql-srv/src/value/encode.rs

@@ -913,9 +913,10 @@ mod tests {
                         table: String::new(),
                         column: String::new(),
                         coltype: $ct,
-                        column_length: None,
+                        column_length: 0,
                         colflags: ColumnFlags::empty(),
                         character_set: 33,
+                        decimals: 0,
                     };
 
                     if !$sig {

mysql-srv/src/writers.rs

@@ -111,7 +111,7 @@ fn col_enc_len(c: &Column) -> usize {
         + (1 + 2 + 4 + 1 + 2 + 1 + 2)
 }
 
-// See https://dev.mysql.com/doc/internals/en/com-query-response.html for documentation
+// See https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_query_response_text_resultset_column_definition.html for documentation
 fn write_column_definition(c: &Column, buf: &mut Vec<u8>) {
     // The following unwraps are fine because writes to a Vec can't fail
 
@@ -135,14 +135,13 @@ fn write_column_definition(c: &Column, buf: &mut Vec<u8>) {
     //
     // TODO: `column_length` should not be an option. Using 1024 as a default is not necessarily
     // correct
-    buf.write_u32::<LittleEndian>(c.column_length.unwrap_or(1024))
-        .unwrap();
+    buf.write_u32::<LittleEndian>(c.column_length).unwrap();
     // Column Type (1 byte)
     buf.write_u8(c.coltype as u8).unwrap();
     // Column Flags (2 bytes)
     buf.write_u16::<LittleEndian>(c.colflags.bits()).unwrap();
     // Decimals (1 byte) - maximum shown decimal digits
-    buf.write_all(&[0x00]).unwrap(); // decimals
+    buf.write_all(&[c.decimals]).unwrap(); // decimals
     buf.write_all(&[0x00, 0x00]).unwrap(); // unused
 }