Parse MySQL column default value (#110)

* Parse MySQL column default value

* Fixup

* clippy

* Fix

* clippy

* Add ColumnDefault::Null

* Parse extra to determine if it's default expression

* Customized parsing logic for MySQL and MariaDB column default

* Remove current date and time from `ColumnDefault`

* Add `ColumnDefault::CustomExpr`

* Simplify

* Parse custom expression

* fmt

* Fix

* use i64

* Tweaks

* MariaDB >= 10.2.7

---------

Co-authored-by: Chris Tsang <[email protected]>

src/mysql/def/column.rs

@@ -41,9 +41,13 @@ pub enum ColumnKey {
 
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "with-serde", derive(Serialize, Deserialize))]
-pub struct ColumnDefault {
-    /// default value expression
-    pub expr: String,
+pub enum ColumnDefault {
+    Null,
+    Int(i64),
+    Real(f64),
+    String(String),
+    CustomExpr(String),
+    CurrentTimestamp,
 }
 
 #[derive(Clone, Debug, PartialEq)]

src/mysql/discovery/mod.rs

@@ -93,7 +93,7 @@ impl SchemaDiscovery {
     pub async fn discover_table(&self, info: TableInfo) -> Result<TableDef, SqlxError> {
         let table = SeaRc::new(Alias::new(info.name.as_str()));
         let columns = self
-            .discover_columns(self.schema.clone(), table.clone())
+            .discover_columns(self.schema.clone(), table.clone(), &self.query.system)
             .await?;
         let indexes = self
             .discover_indexes(self.schema.clone(), table.clone())
@@ -114,6 +114,7 @@ impl SchemaDiscovery {
         &self,
         schema: SeaRc<dyn Iden>,
         table: SeaRc<dyn Iden>,
+        system: &SystemInfo,
     ) -> Result<Vec<ColumnInfo>, SqlxError> {
         let rows = self
             .executor
@@ -125,7 +126,7 @@ impl SchemaDiscovery {
             .map(|row| {
                 let result: ColumnQueryResult = row.into();
                 debug_print!("{:?}", result);
-                let column = result.parse();
+                let column = result.parse(system);
                 debug_print!("{:?}", column);
                 column
             })

src/mysql/parser/column.rs

@@ -4,18 +4,20 @@ use crate::{parser::Parser, Name};
 use sea_query::{EscapeBuilder, MysqlQueryBuilder};
 
 impl ColumnQueryResult {
-    pub fn parse(self) -> ColumnInfo {
-        parse_column_query_result(self)
+    pub fn parse(self, system: &SystemInfo) -> ColumnInfo {
+        parse_column_query_result(self, system)
     }
 }
 
-pub fn parse_column_query_result(result: ColumnQueryResult) -> ColumnInfo {
+pub fn parse_column_query_result(result: ColumnQueryResult, system: &SystemInfo) -> ColumnInfo {
+    let col_type = parse_column_type(&mut Parser::new(&result.column_type));
+    let default = parse_column_default(&col_type, result.column_default, &result.extra, system);
     ColumnInfo {
         name: result.column_name,
-        col_type: parse_column_type(&mut Parser::new(&result.column_type)),
+        col_type,
         null: parse_column_null(&result.is_nullable),
         key: parse_column_key(&result.column_key),
-        default: parse_column_default(result.column_default),
+        default,
         extra: parse_column_extra(&mut Parser::new(&result.extra)),
         expression: match result.generation_expression {
             Some(generation_expression) => parse_generation_expression(generation_expression),
@@ -260,11 +262,23 @@ pub fn parse_column_key(string: &str) -> ColumnKey {
     }
 }
 
-pub fn parse_column_default(column_default: Option<String>) -> Option<ColumnDefault> {
-    match column_default {
+pub fn parse_column_default(
+    col_type: &Type,
+    default: Option<String>,
+    extra: &str,
+    system: &SystemInfo,
+) -> Option<ColumnDefault> {
+    match default {
         Some(default) => {
             if !default.is_empty() {
-                Some(ColumnDefault { expr: default })
+                let default_value = if system.is_mysql() && system.version >= 80000 {
+                    parse_mysql_8_default(default, extra)
+                } else if system.is_maria_db() && system.version >= 100207 {
+                    parse_mariadb_10_default(default)
+                } else {
+                    parse_mysql_5_default(default, col_type)
+                };
+                Some(default_value)
             } else {
                 None
             }
@@ -273,6 +287,52 @@ pub fn parse_column_default(column_default: Option<String>) -> Option<ColumnDefa
     }
 }
 
+pub fn parse_mysql_5_default(default: String, col_type: &Type) -> ColumnDefault {
+    let is_date_time = matches!(col_type, Type::DateTime(_) | Type::Timestamp(_));
+    if is_date_time && default == "CURRENT_TIMESTAMP" {
+        ColumnDefault::CurrentTimestamp
+    } else if let Ok(int) = default.parse() {
+        ColumnDefault::Int(int)
+    } else if let Ok(real) = default.parse() {
+        ColumnDefault::Real(real)
+    } else {
+        ColumnDefault::String(default)
+    }
+}
+
+pub fn parse_mysql_8_default(default: String, extra: &str) -> ColumnDefault {
+    let is_expression = extra.contains("DEFAULT_GENERATED");
+    if is_expression && default == "CURRENT_TIMESTAMP" {
+        ColumnDefault::CurrentTimestamp
+    } else if is_expression && default == "NULL" {
+        ColumnDefault::Null
+    } else if let Ok(int) = default.parse() {
+        ColumnDefault::Int(int)
+    } else if let Ok(real) = default.parse() {
+        ColumnDefault::Real(real)
+    } else if is_expression {
+        ColumnDefault::CustomExpr(default)
+    } else {
+        ColumnDefault::String(default)
+    }
+}
+
+pub fn parse_mariadb_10_default(default: String) -> ColumnDefault {
+    if default.starts_with('\'') && default.ends_with('\'') {
+        ColumnDefault::String(default[1..(default.len() - 1)].into())
+    } else if let Ok(int) = default.parse() {
+        ColumnDefault::Int(int)
+    } else if let Ok(real) = default.parse() {
+        ColumnDefault::Real(real)
+    } else if default == "current_timestamp()" {
+        ColumnDefault::CurrentTimestamp
+    } else if default == "NULL" {
+        ColumnDefault::Null
+    } else {
+        ColumnDefault::CustomExpr(default)
+    }
+}
+
 pub fn parse_generation_expression(string: String) -> Option<ColumnExpression> {
     if string.is_empty() {
         None

src/mysql/writer/column.rs

@@ -1,6 +1,7 @@
-use crate::mysql::def::{CharSet, ColumnInfo, NumericAttr, StringAttr, Type};
+use crate::mysql::def::{CharSet, ColumnDefault, ColumnInfo, NumericAttr, StringAttr, Type};
 use sea_query::{
-    Alias, BlobSize, ColumnDef, DynIden, EscapeBuilder, Iden, IntoIden, MysqlQueryBuilder,
+    Alias, BlobSize, ColumnDef, DynIden, EscapeBuilder, Expr, Iden, IntoIden, Keyword,
+    MysqlQueryBuilder, SimpleExpr,
 };
 use std::fmt::Write;
 
@@ -15,10 +16,16 @@ impl ColumnInfo {
             col_def.auto_increment();
         }
         let mut extras = Vec::new();
-        if let Some(default) = self.default.as_ref() {
-            let mut string = "".to_owned();
-            write!(&mut string, "DEFAULT {}", default.expr).unwrap();
-            extras.push(string);
+        if let Some(default) = &self.default {
+            let default_expr: SimpleExpr = match default {
+                ColumnDefault::Null => Option::<bool>::None.into(),
+                ColumnDefault::Int(int) => (*int).into(),
+                ColumnDefault::Real(double) => (*double).into(),
+                ColumnDefault::String(string) => string.into(),
+                ColumnDefault::CustomExpr(string) => Expr::cust(string),
+                ColumnDefault::CurrentTimestamp => Keyword::CurrentTimestamp.into(),
+            };
+            col_def.default(default_expr);
         }
         if self.extra.on_update_current_timestamp {
             extras.push("ON UPDATE CURRENT_TIMESTAMP".to_owned());

src/mysql/writer/table.rs

@@ -119,9 +119,7 @@ mod tests {
                         null: false,
                         key: ColumnKey::NotKey,
                         default: Some(
-                            ColumnDefault {
-                                expr: "CURRENT_TIMESTAMP".to_owned(),
-                            },
+                            ColumnDefault::CurrentTimestamp,
                         ),
                         extra: ColumnExtra {
                             auto_increment: false,
@@ -219,9 +217,7 @@ mod tests {
                         null: false,
                         key: ColumnKey::NotKey,
                         default: Some(
-                            ColumnDefault {
-                                expr: "CURRENT_TIMESTAMP".to_owned(),
-                            },
+                            ColumnDefault::CurrentTimestamp,
                         ),
                         extra: ColumnExtra {
                             auto_increment: false,

tests/live/mysql/src/main.rs

@@ -2,7 +2,7 @@ use pretty_assertions::assert_eq;
 use regex::Regex;
 use sea_schema::mysql::{def::TableDef, discovery::SchemaDiscovery};
 use sea_schema::sea_query::{
-    Alias, ColumnDef, ForeignKey, ForeignKeyAction, Index, MysqlQueryBuilder, Table,
+    Alias, ColumnDef, Expr, ForeignKey, ForeignKeyAction, Index, MysqlQueryBuilder, Table,
     TableCreateStatement, TableRef,
 };
 use sqlx::{MySql, MySqlPool, Pool};
@@ -206,7 +206,26 @@ fn create_order_table() -> TableCreateStatement {
         .col(
             ColumnDef::new(Alias::new("placed_at"))
                 .date_time()
-                .not_null(),
+                .not_null()
+                .default(Expr::current_timestamp()),
+        )
+        .col(
+            ColumnDef::new(Alias::new("updated"))
+                .date_time()
+                .not_null()
+                .default("2023-06-07 16:24:00"),
+        )
+        .col(
+            ColumnDef::new(Alias::new("net_weight"))
+                .double()
+                .not_null()
+                .default(10.05),
+        )
+        .col(
+            ColumnDef::new(Alias::new("priority"))
+                .integer()
+                .not_null()
+                .default(5),
         )
         .index(
             Index::create()