fix(dalgorm): make DropIndexes idempotent by skipping missing indexes

[DoDiODev]

Summary

Make Dalgorm.DropIndexes idempotent by skipping indexes that are not present, so dropping an already-absent index no longer aborts a migration.

Problem

Dalgorm.DropIndexes calls GORM's Migrator().DropIndex, which emits a bare DROP INDEX without IF EXISTS. On PostgreSQL this fails hard with ERROR: index "..." does not exist (SQLSTATE 42704) when the target index is missing, causing the migrator to panic and the server to crash on startup.

This is reproducible on PostgreSQL with the migration change _tool_sonarqube_issue_code_blocks.component type to text, which unconditionally drops idx__tool_sonarqube_issue_code_blocks_component. That index is no longer present after the earlier modify component type to varchar(500) migration rewrites the column via ChangeColumnsType (rename column, then AutoMigrate skips the name-colliding index, then the old column and its index are dropped). The result is a table with component varchar(500) and no component index, so the later unconditional DropIndexes aborts.

Observed panic:

ERROR: index "idx__tool_sonarqube_issue_code_blocks_component" does not exist (SQLSTATE 42704)
DROP INDEX "idx__tool_sonarqube_issue_code_blocks_component"
panic: ... (500)
server/services.InitExecuteMigration()

Fix

Guard each drop with migrator.HasIndex(table, indexName) and skip indexes that do not exist. This makes the operation idempotent and database-neutral while still surfacing genuine drop errors (it does not blanket-swallow errors).

Related

• chore(docker): bump PostgreSQL to 18.1 and MySQL to 8.4.10 #9003 (chore(docker): bump PostgreSQL to 18.1 and MySQL to 8.4.10) surfaces this crash during its PostgreSQL manual gate and recommends this fix be applied first. The two PRs are functionally independent and do not touch overlapping files.

Testing

• go build ./impls/dalgorm/...
• Manual PostgreSQL migration run: with the fix, the previously-crashing migration chain completes and the server reaches ready state; without it, PostgreSQL aborts on the missing index.

A DB-backed unit test was intentionally omitted to avoid introducing an sqlite driver dependency that is not currently in go.mod.

Rollback

Revert this single-file change; behaviour returns to the unconditional drop.