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Use temporary column for add column migration

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Previously the column was added with its final name directly. This could
cause trouble if there was a column with the same name removed during
the same migration.
This commit is contained in:
fabianlindfors 2021-12-31 17:20:25 +01:00
parent 40ba58b313
commit c54190bfc1
1 changed files with 37 additions and 9 deletions
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46
src/migrations/add_column.rs
View File

@ -10,6 +10,15 @@ pub struct AddColumn {
}
impl AddColumn {
fn temp_column_name(&self, ctx: &Context) -> String {
format!(
"{}_temp_column_{}_{}",
ctx.prefix(),
self.table,
self.column.name,
)
}
fn trigger_name(&self, ctx: &Context) -> String {
format!(
"{}_add_column_{}_{}",
@ -40,9 +49,10 @@ impl Action for AddColumn {
fn run(&self, ctx: &Context, db: &mut dyn Conn, schema: &Schema) -> anyhow::Result<()> {
let table = schema.get_table(db, &self.table)?;
let temp_column_name = self.temp_column_name(ctx);
let mut definition_parts = vec![
self.column.name.to_string(),
temp_column_name.to_string(),
self.column.data_type.to_string(),
];
@ -93,7 +103,7 @@ impl Action for AddColumn {
DECLARE
{declarations}
BEGIN
NEW.{column_name} = {up};
NEW.{temp_column_name} = {up};
END;
END IF;
RETURN NEW;
@ -103,7 +113,7 @@ impl Action for AddColumn {
DROP TRIGGER IF EXISTS {trigger_name} ON {table};
CREATE TRIGGER {trigger_name} BEFORE UPDATE OR INSERT ON {table} FOR EACH ROW EXECUTE PROCEDURE {trigger_name}();
",
column_name = self.column.name,
temp_column_name = temp_column_name,
trigger_name = self.trigger_name(ctx),
up = up,
table = self.table,
@ -114,7 +124,7 @@ impl Action for AddColumn {
// Backfill values in batches
if self.up.is_some() {
common::batch_touch_rows(db, &table.real_name, &self.column.name)?;
common::batch_touch_rows(db, &table.real_name, &temp_column_name)?;
}
// Add a temporary NOT NULL constraint if the column shouldn't be nullable.
@ -130,7 +140,7 @@ impl Action for AddColumn {
",
table = self.table,
constraint_name = self.not_null_constraint_name(&ctx),
column = self.column.name,
column = temp_column_name,
);
db.run(&query)?;
}
@ -138,7 +148,9 @@ impl Action for AddColumn {
Ok(())
}
fn complete(&self, ctx: &Context, db: &mut dyn Conn, _schema: &Schema) -> anyhow::Result<()> {
fn complete(&self, ctx: &Context, db: &mut dyn Conn, schema: &Schema) -> anyhow::Result<()> {
let table = schema.get_table(db, &self.table)?;
// Remove triggers and procedures
let query = format!(
"
@ -174,7 +186,7 @@ impl Action for AddColumn {
ALTER COLUMN {column} SET NOT NULL
",
table = self.table,
column = self.column.name,
column = self.temp_column_name(ctx),
);
db.run(&query)?;
@ -190,10 +202,26 @@ impl Action for AddColumn {
db.run(&query)?;
}
// Rename the temporary column to its real name
db.run(&format!(
"
ALTER TABLE {table}
RENAME COLUMN {temp_column_name} TO {column_name}
",
table = table.real_name,
temp_column_name = self.temp_column_name(ctx),
column_name = self.column.name,
))?;
Ok(())
}
fn update_schema(&self, _ctx: &Context, _schema: &mut Schema) -> anyhow::Result<()> {
fn update_schema(&self, ctx: &Context, schema: &mut Schema) -> anyhow::Result<()> {
schema.change_table(&self.table, |table_changes| {
table_changes.change_column(&self.column.name, |column_changes| {
column_changes.set_column(&self.temp_column_name(ctx));
})
});
Ok(())
}
@ -216,7 +244,7 @@ impl Action for AddColumn {
DROP COLUMN IF EXISTS {column}
",
table = self.table,
column = self.column.name,
column = self.temp_column_name(ctx),
);
db.run(&query)?;