@@ -43,7 +43,7 @@ impl RemoveColumn {
4343 )
4444 }
4545
46− fn null_constraint_trigger_name(&self, ctx: &MigrationContext) -> String {
46+ fn not_null_constraint_trigger_name(&self, ctx: &MigrationContext) -> String {
4747 format!(
4848 "{}_remove_column_{}_{}_nn",
4949 ctx.prefix(),
@@ -51,6 +51,15 @@ impl RemoveColumn {
5151 self.column
5252 )
5353 }
54+
55+ fn not_null_constraint_name(&self, ctx: &MigrationContext) -> String {
56+ format!(
57+ "{}_add_column_not_null_{}_{}",
58+ ctx.prefix(),
59+ self.table,
60+ self.column
61+ )
62+ }
5463}
5564
5665#[typetag::serde(name = "remove_column")]
@@ -132,6 +141,7 @@ impl Action for RemoveColumn {
132141
133142 let maybe_null_check = if !column.nullable {
134143 // Replace NOT NULL constraint with a constraint trigger that only triggers on the old schema.
144+ // We will add a null check to the down function on the new schema below as well to cover both cases.
135145 // As we are using a complex down function, we must remove the NOT NULL check for the new schema.
136146 // NOT NULL is not checked at the end of a transaction, but immediately upon update.
137147 let query = format!(
@@ -157,7 +167,7 @@ impl Action for RemoveColumn {
157167 EXECUTE PROCEDURE {trigger_name}();
158168 "#,
159169 table = self.table,
160− trigger_name = self.null_constraint_trigger_name(ctx),
170+ trigger_name = self.not_null_constraint_trigger_name(ctx),
161171 column = self.column,
162172 );
163173 db.run(&query)
@@ -236,7 +246,6 @@ impl Action for RemoveColumn {
236246 from_table_real = from_table.real_name,
237247 column_name = self.column,
238248 trigger_name = self.trigger_name(ctx),
239− // declarations = declarations.join("\n"),
240249 );
241250 db.run(&query).context("failed to create down trigger")?;
242251
@@ -310,8 +319,6 @@ impl Action for RemoveColumn {
310319 }
311320 }
312321
313− if !column.nullable {}
314−
315322 Ok(())
316323 }
317324
@@ -347,7 +354,7 @@ impl Action for RemoveColumn {
347354 column = self.column,
348355 trigger_name = self.trigger_name(ctx),
349356 reverse_trigger_name = self.reverse_trigger_name(ctx),
350− null_trigger_name = self.null_constraint_trigger_name(ctx),
357+ null_trigger_name = self.not_null_constraint_trigger_name(ctx),
351358 );
352359 db.run(&query)
353360 .context("failed to drop column and down trigger")?;
@@ -364,17 +371,70 @@ impl Action for RemoveColumn {
364371 }
365372
366373 fn abort(&self, ctx: &MigrationContext, db: &mut dyn Conn) -> anyhow::Result<()> {
367− // We might have removed the NOT NULL check so we reinstate it
368− db.run(&format!(
369− r#"
370− ALTER TABLE {table}
371− ALTER COLUMN {column}
372− SET NOT NULL
373− "#,
374− table = self.table,
375− column = self.column
376− ))
377− .context("failed to reinstate column not null constraint")?;
374+ // We might have temporaily removed the NOT NULL check and have to reinstate it
375+ let has_not_null_function = !db
376+ .query_with_params(
377+ "
378+ SELECT routine_name
379+ FROM information_schema.routines
380+ WHERE routine_schema = 'public'
381+ AND routine_name = $1
382+ ",
383+ &[&self.not_null_constraint_trigger_name(ctx)],
384+ )
385+ .context("failed to get any NOT NULL function")?
386+ .is_empty();
387+
388+ if has_not_null_function {
389+ // Make column NOT NULL again without taking any long lived locks with a temporary constraint
390+ let query = format!(
391+ r#"
392+ ALTER TABLE "{table}"
393+ ADD CONSTRAINT "{constraint_name}"
394+ CHECK ("{column}" IS NOT NULL) NOT VALID
395+ "#,
396+ table = self.table,
397+ constraint_name = self.not_null_constraint_name(ctx),
398+ column = self.column,
399+ );
400+ db.run(&query)
401+ .context("failed to add NOT NULL constraint")?;
402+
403+ let query = format!(
404+ r#"
405+ ALTER TABLE "{table}"
406+ VALIDATE CONSTRAINT "{constraint_name}"
407+ "#,
408+ table = self.table,
409+ constraint_name = self.not_null_constraint_name(ctx),
410+ );
411+ db.run(&query)
412+ .context("failed to validate NOT NULL constraint")?;
413+
414+ // This ALTER TABLE call will not require any exclusive locks as it can use the validated constraint from above
415+ db.run(&format!(
416+ r#"
417+ ALTER TABLE {table}
418+ ALTER COLUMN {column}
419+ SET NOT NULL
420+ "#,
421+ table = self.table,
422+ column = self.column
423+ ))
424+ .context("failed to reinstate column NOT NULL")?;
425+
426+ // Drop the temporary constraint
427+ let query = format!(
428+ r#"
429+ ALTER TABLE "{table}"
430+ DROP CONSTRAINT "{constraint_name}"
431+ "#,
432+ table = self.table,
433+ constraint_name = self.not_null_constraint_name(ctx),
434+ );
435+ db.run(&query)
436+ .context("failed to drop NOT NULL constraint")?;
437+ }
378438
379439 // Remove function and trigger
380440 db.run(&format!(
@@ -385,7 +445,7 @@ impl Action for RemoveColumn {
385445 "#,
386446 trigger_name = self.trigger_name(ctx),
387447 reverse_trigger_name = self.reverse_trigger_name(ctx),
388− null_trigger_name = self.null_constraint_trigger_name(ctx),
448+ null_trigger_name = self.not_null_constraint_trigger_name(ctx),
389449 ))
390450 .context("failed to drop down trigger")?;
391451