Avoid doing sequential database queries to load the namespaces and the
routes of projects and namespaces.
This results in the following query:
```sql
SELECT "projects"."id" AS t0_r0,
"projects"."name" AS t0_r1,
"projects"."path" AS t0_r2,
"projects"."description" AS t0_r3,
"projects"."created_at" AS t0_r4,
"projects"."updated_at" AS t0_r5,
"projects"."creator_id" AS t0_r6,
"projects"."namespace_id" AS t0_r7,
"projects"."last_activity_at" AS t0_r8,
"projects"."import_url" AS t0_r9,
"projects"."visibility_level" AS t0_r10,
"projects"."archived" AS t0_r11,
"projects"."avatar" AS t0_r12,
"projects"."import_status" AS t0_r13,
"projects"."star_count" AS t0_r14,
"projects"."import_type" AS t0_r15,
"projects"."import_source" AS t0_r16,
"projects"."import_error" AS t0_r17,
"projects"."ci_id" AS t0_r18,
"projects"."shared_runners_enabled" AS t0_r19,
"projects"."runners_token" AS t0_r20,
"projects"."build_coverage_regex" AS t0_r21,
"projects"."build_allow_git_fetch" AS t0_r22,
"projects"."build_timeout" AS t0_r23,
"projects"."pending_delete" AS t0_r24,
"projects"."public_builds" AS t0_r25,
"projects"."last_repository_check_failed" AS t0_r26,
"projects"."last_repository_check_at" AS t0_r27,
"projects"."container_registry_enabled" AS t0_r28,
"projects"."only_allow_merge_if_pipeline_succeeds" AS t0_r29,
"projects"."has_external_issue_tracker" AS t0_r30,
"projects"."repository_storage" AS t0_r31,
"projects"."request_access_enabled" AS t0_r32,
"projects"."has_external_wiki" AS t0_r33,
"projects"."ci_config_path" AS t0_r34,
"projects"."lfs_enabled" AS t0_r35,
"projects"."description_html" AS t0_r36,
"projects"."only_allow_merge_if_all_discussions_are_resolved" AS t0_r37,
"projects"."printing_merge_request_link_enabled" AS t0_r38,
"projects"."auto_cancel_pending_pipelines" AS t0_r39,
"projects"."import_jid" AS t0_r40,
"projects"."cached_markdown_version" AS t0_r41,
"projects"."delete_error" AS t0_r42,
"projects"."last_repository_updated_at" AS t0_r43,
"projects"."storage_version" AS t0_r44,
"projects"."resolve_outdated_diff_discussions" AS t0_r45,
"projects"."repository_read_only" AS t0_r46,
"projects"."merge_requests_ff_only_enabled" AS t0_r47,
"projects"."merge_requests_rebase_enabled" AS t0_r48,
"projects"."jobs_cache_index" AS t0_r49,
"projects"."pages_https_only" AS t0_r50,
"projects"."remote_mirror_available_overridden" AS t0_r51,
"projects"."pool_repository_id" AS t0_r52,
"projects"."runners_token_encrypted" AS t0_r53,
"projects"."bfg_object_map" AS t0_r54,
"namespaces"."id" AS t1_r0,
"namespaces"."name" AS t1_r1,
"namespaces"."path" AS t1_r2,
"namespaces"."owner_id" AS t1_r3,
"namespaces"."created_at" AS t1_r4,
"namespaces"."updated_at" AS t1_r5,
"namespaces"."type" AS t1_r6,
"namespaces"."description" AS t1_r7,
"namespaces"."avatar" AS t1_r8,
"namespaces"."share_with_group_lock" AS t1_r9,
"namespaces"."visibility_level" AS t1_r10,
"namespaces"."request_access_enabled" AS t1_r11,
"namespaces"."description_html" AS t1_r12,
"namespaces"."lfs_enabled" AS t1_r13,
"namespaces"."parent_id" AS t1_r14,
"namespaces"."require_two_factor_authentication" AS t1_r15,
"namespaces"."two_factor_grace_period" AS t1_r16,
"namespaces"."cached_markdown_version" AS t1_r17,
"namespaces"."runners_token" AS t1_r18,
"namespaces"."runners_token_encrypted" AS t1_r19,
"routes"."id" AS t2_r0,
"routes"."source_id" AS t2_r1,
"routes"."source_type" AS t2_r2,
"routes"."path" AS t2_r3,
"routes"."created_at" AS t2_r4,
"routes"."updated_at" AS t2_r5,
"routes"."name" AS t2_r6,
"routes_projects"."id" AS t3_r0,
"routes_projects"."source_id" AS t3_r1,
"routes_projects"."source_type" AS t3_r2,
"routes_projects"."path" AS t3_r3,
"routes_projects"."created_at" AS t3_r4,
"routes_projects"."updated_at" AS t3_r5,
"routes_projects"."name" AS t3_r6
FROM "projects"
LEFT OUTER JOIN "namespaces" ON "namespaces"."id" = "projects"."namespace_id"
LEFT OUTER JOIN "routes" ON "routes"."source_id" = "namespaces"."id"
AND "routes"."source_type" = $1
LEFT OUTER JOIN "routes" "routes_projects" ON "routes_projects"."source_id" = "projects"."id"
AND "routes_projects"."source_type" = $2
LEFT OUTER JOIN "project_repositories" ON "projects"."id" = "project_repositories"."project_id"
WHERE ("projects"."storage_version" IS NULL
OR "projects"."storage_version" = 0)
AND "project_repositories"."project_id" IS NULL
AND ("projects"."id" BETWEEN $3 AND $4);
-- [["source_type", "Namespace"],
-- ["source_type", "Project"],
-- ["id", 1],
-- ["id", 4]]
```
On GitLab.com, we saw numerous duplicate disk entry inserts because
the migration was not taking the routes table into account. We now
implement this in the migration to be consistent.
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/56061
