4c316ae · reshape · git.iko.soy

git.iko.soy/reshape

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Use safe NOT NULL checking during abort for complex remove column action

4c316aefabianlindfors3 years ago

src/migrations/remove_column.rs+78−18

compare with main

unifiedsplit

@@ -43,7 +43,7 @@ impl RemoveColumn {

43 )

44 }

46− fn null_constraint_trigger_name(&self, ctx: &MigrationContext) -> String {

46+ fn not_null_constraint_trigger_name(&self, ctx: &MigrationContext) -> String {

47 format!(

48 "{}_remove_column_{}_{}_nn",

49 ctx.prefix(),

@@ -51,6 +51,15 @@ impl RemoveColumn {

51 self.column

52 )

53 }

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+ }

54}

63}

56#[typetag::serde(name = "remove_column")]

65#[typetag::serde(name = "remove_column")]

@@ -132,6 +141,7 @@ impl Action for RemoveColumn {

132

141

133 let maybe_null_check = if !column.nullable {

142 let maybe_null_check = if !column.nullable {

134 // Replace NOT NULL constraint with a constraint trigger that only triggers on the old schema.

143 // 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.

135 // As we are using a complex down function, we must remove the NOT NULL check for the new schema.

145 // As we are using a complex down function, we must remove the NOT NULL check for the new schema.

136 // NOT NULL is not checked at the end of a transaction, but immediately upon update.

146 // NOT NULL is not checked at the end of a transaction, but immediately upon update.

137 let query = format!(

147 let query = format!(

@@ -157,7 +167,7 @@ impl Action for RemoveColumn {

157 EXECUTE PROCEDURE {trigger_name}();

167 EXECUTE PROCEDURE {trigger_name}();

158 "#,

168 "#,

159 table = self.table,

169 table = self.table,

160− trigger_name = self.null_constraint_trigger_name(ctx),

170+ trigger_name = self.not_null_constraint_trigger_name(ctx),

161 column = self.column,

171 column = self.column,

162 );

172 );

163 db.run(&query)

173 db.run(&query)

@@ -236,7 +246,6 @@ impl Action for RemoveColumn {

236 from_table_real = from_table.real_name,

246 from_table_real = from_table.real_name,

237 column_name = self.column,

247 column_name = self.column,

238 trigger_name = self.trigger_name(ctx),

248 trigger_name = self.trigger_name(ctx),

239− // declarations = declarations.join("\n"),

240 );

249 );

241 db.run(&query).context("failed to create down trigger")?;

250 db.run(&query).context("failed to create down trigger")?;

242

251

@@ -310,8 +319,6 @@ impl Action for RemoveColumn {

310 }

319 }

311 }

320 }

312

321

313− if !column.nullable {}

314−

315 Ok(())

322 Ok(())

316 }

323 }

317

324

@@ -347,7 +354,7 @@ impl Action for RemoveColumn {

347 column = self.column,

354 column = self.column,

348 trigger_name = self.trigger_name(ctx),

355 trigger_name = self.trigger_name(ctx),

349 reverse_trigger_name = self.reverse_trigger_name(ctx),

356 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),

351 );

358 );

352 db.run(&query)

359 db.run(&query)

353 .context("failed to drop column and down trigger")?;

360 .context("failed to drop column and down trigger")?;

@@ -364,17 +371,70 @@ impl Action for RemoveColumn {

364 }

371 }

365

372

366 fn abort(&self, ctx: &MigrationContext, db: &mut dyn Conn) -> anyhow::Result<()> {

373 fn abort(&self, ctx: &MigrationContext, db: &mut dyn Conn) -> anyhow::Result<()> {

367− // We might have removed the NOT NULL check so we reinstate it

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

368− db.run(&format!(

390+ let query = format!(

369− r#"

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#"

370− ALTER TABLE {table}

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}

371− ALTER COLUMN {column}

418+ ALTER COLUMN {column}

372− SET NOT NULL

419+ SET NOT NULL

373− "#,

420+ "#,

374− table = self.table,

421+ table = self.table,

375− column = self.column

422+ column = self.column

376− ))

423+ ))

377− .context("failed to reinstate column not null constraint")?;

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+ }

378

438

379 // Remove function and trigger

439 // Remove function and trigger

380 db.run(&format!(

440 db.run(&format!(

@@ -385,7 +445,7 @@ impl Action for RemoveColumn {

385 "#,

445 "#,

386 trigger_name = self.trigger_name(ctx),

446 trigger_name = self.trigger_name(ctx),

387 reverse_trigger_name = self.reverse_trigger_name(ctx),

447 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),

389 ))

449 ))

390 .context("failed to drop down trigger")?;

450 .context("failed to drop down trigger")?;

391

451