Finalize conversion to bigint for ci_build_trace_chunks

1. Ensure the migration of `build_id` to `bigint` is completed
2. Copy index and FK
3. Swap columns

See https://gitlab.com/gitlab-org/gitlab/-/issues/328443.

Changelog: other

db/post_migrate/20210714015537_finalize_ci_build_trace_chunks_bigint_conversion.rb

+# frozen_string_literal: true
+
+class FinalizeCiBuildTraceChunksBigintConversion < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  TABLE_NAME = 'ci_build_trace_chunks'
+
+  def up
+    ensure_batched_background_migration_is_finished(
+      job_class_name: 'CopyColumnUsingBackgroundMigrationJob',
+      table_name: TABLE_NAME,
+      column_name: 'id',
+      job_arguments: [['build_id'], ['build_id_convert_to_bigint']]
+    )
+
+    swap
+  end
+
+  def down
+    swap
+  end
+
+  private
+
+  def swap
+    # This is to replace the existing "index_ci_build_trace_chunks_on_build_id_and_chunk_index" UNIQUE, btree (build_id, chunk_index)
+    add_concurrent_index TABLE_NAME, [:build_id_convert_to_bigint, :chunk_index], unique: true, name: 'i_ci_build_trace_chunks_build_id_convert_to_bigint_chunk_index'
+
+    # Add a foreign key on `build_id_convert_to_bigint` before we swap the columns and drop the old FK ()
+    add_concurrent_foreign_key TABLE_NAME, :ci_builds, column: :build_id_convert_to_bigint, on_delete: :cascade, name: 'fk_rails_1013b761f2_tmp'
+
+    with_lock_retries(raise_on_exhaustion: true) do
+      # We'll need  ACCESS EXCLUSIVE lock on the related tables,
+      # lets make sure it can be acquired from the start
+      execute "LOCK TABLE #{TABLE_NAME}, ci_builds IN ACCESS EXCLUSIVE MODE"
+
+      # Swap column names
+      temp_name = 'build_id_tmp'
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:build_id)} TO #{quote_column_name(temp_name)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:build_id_convert_to_bigint)} TO #{quote_column_name(:build_id)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(temp_name)} TO #{quote_column_name(:build_id_convert_to_bigint)}"
+
+      # We need to update the trigger function in order to make PostgreSQL to
+      # regenerate the execution plan for it. This is to avoid type mismatch errors like
+      # "type of parameter 15 (bigint) does not match that when preparing the plan (integer)"
+      function_name = Gitlab::Database::UnidirectionalCopyTrigger.on_table(TABLE_NAME).name(:build_id, :build_id_convert_to_bigint)
+      execute "ALTER FUNCTION #{quote_table_name(function_name)} RESET ALL"
+
+      # Swap defaults
+      change_column_default TABLE_NAME, :build_id, nil
+      change_column_default TABLE_NAME, :build_id_convert_to_bigint, 0
+
+      # Rename the index on the `bigint` column to match the new column name
+      # (we already hold an exclusive lock, so no need to use DROP INDEX CONCURRENTLY here)
+      execute 'DROP INDEX index_ci_build_trace_chunks_on_build_id_and_chunk_index'
+      rename_index TABLE_NAME, 'i_ci_build_trace_chunks_build_id_convert_to_bigint_chunk_index', 'index_ci_build_trace_chunks_on_build_id_and_chunk_index'
+
+      # Drop original FK on the old int4 `build_id` (fk_rails_1013b761f2)
+      remove_foreign_key TABLE_NAME, name: 'fk_rails_1013b761f2'
+      # We swapped the columns but the FK for buil_id is still using the temporary name for the build_id_convert_to_bigint column
+      # So we have to also swap the FK name now that we dropped the other one with the same
+      rename_constraint(TABLE_NAME, 'fk_rails_1013b761f2_tmp', 'fk_rails_1013b761f2')
+    end
+  end
+end

db/schema_migrations/20210714015537

+2f6441a5d5e3c4aad6b88c3944436dab213b7eeb2f35453657ffac8c0733efc1
\ No newline at end of file

db/structure.sql

@@ -10475,13 +10475,13 @@ ALTER SEQUENCE ci_build_report_results_build_id_seq OWNED BY ci_build_report_res
 
 CREATE TABLE ci_build_trace_chunks (
     id bigint NOT NULL,
-    build_id integer NOT NULL,
+    build_id_convert_to_bigint integer DEFAULT 0 NOT NULL,
     chunk_index integer NOT NULL,
     data_store integer NOT NULL,
     raw_data bytea,
     checksum bytea,
     lock_version integer DEFAULT 0 NOT NULL,
-    build_id_convert_to_bigint bigint DEFAULT 0 NOT NULL
+    build_id bigint NOT NULL
 );
 
 CREATE SEQUENCE ci_build_trace_chunks_id_seq