db: add (pubkey, updated_at) index

[louisinger]

@sekulicd @altafan please review

Summary by CodeRabbit

• Chores
  • Added database migrations for performance optimization across supported database systems.

[coderabbitai]

Walkthrough

This PR adds database migrations to create an index on the vtxo table across PostgreSQL and SQLite databases. The index is created on the (pubkey, updated_at) column combination, with corresponding down-migrations to drop the index if needed.

Changes

Cohort / File(s)	Summary
PostgreSQL Migrations internal/infrastructure/db/postgres/migration/20260318074150_vtxo_indexes.up.sql, internal/infrastructure/db/postgres/migration/20260318074150_vtxo_indexes.down.sql	Adds/drops index idx_vtxo_pubkey_updated_at on vtxo table for (pubkey, updated_at) columns.
SQLite Migrations internal/infrastructure/db/sqlite/migration/20260318074028_vtxo_indexes.up.sql, internal/infrastructure/db/sqlite/migration/20260318074028_vtxo_indexes.down.sql	Adds/drops index idx_vtxo_pubkey_updated_at on vtxo table for (pubkey, updated_at) columns.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely describes the primary change: adding a database index on (pubkey, updated_at) columns, which matches all four migration files added.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

📝 Coding Plan

• Generate coding plan for human review comments

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[arkanaai]

🔍 Review — db: add (pubkey, updated_at) index

+6 lines, 4 files — Adds a composite index (pubkey, updated_at) on the vtxo table for both Postgres and SQLite.

Assessment: ✅ LGTM

Clean, minimal migration. A few notes:

• Column order is correct for queries filtering by pubkey then sorting/filtering by updated_at — this matches the common access pattern for fetching a user's VTXOs ordered by recency.
• IF NOT EXISTS / IF EXISTS guards on both up and down — safe for idempotent re-runs.
• Postgres & SQLite parity — identical index definition, consistent naming.
• Related to optimize GetVtxoChain with marker-based bulk preloading #973 — the GetVtxoChain optimization PR benefits from faster pubkey+time lookups, reducing query latency alongside the marker-based bulk preloading.

One consideration: On large deployments with millions of VTXOs, this index will add write overhead on every VTXO insert/update. Given that reads on (pubkey, updated_at) are hot-path (wallet sync, VTXO listing), the tradeoff is clearly worth it — just worth noting for operators running high-throughput servers.

[coderabbitai]

🧹 Nitpick comments (1)

internal/infrastructure/db/postgres/migration/20260318074150_vtxo_indexes.up.sql (1)

1-2: Consider CONCURRENTLY for production deployments with large tables.

The index design is correct for the query patterns in SelectVtxosWithPubkeys and SelectPendingSpentVtxosWithPubkeys. However, standard CREATE INDEX acquires a lock that blocks writes on the vtxo table until completion. For large tables in production, consider using:

CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_vtxo_pubkey_updated_at
    ON vtxo (pubkey, updated_at);

Note: CONCURRENTLY cannot run inside a transaction block, so this may require adjusting how migrations are applied if your migration tool wraps statements in transactions.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In
`@internal/infrastructure/db/postgres/migration/20260318074150_vtxo_indexes.up.sql`
around lines 1 - 2, The CREATE INDEX currently defined for
idx_vtxo_pubkey_updated_at on table vtxo will take a write lock on vtxo for the
duration of the operation; update the migration to create the index CONCURRENTLY
(i.e., use CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_vtxo_pubkey_updated_at ON
vtxo (pubkey, updated_at)) so writes are not blocked in production, and ensure
your migration runner does not wrap this statement in a transaction (or split it
out) since CONCURRENTLY cannot run inside a transaction block.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In
`@internal/infrastructure/db/postgres/migration/20260318074150_vtxo_indexes.up.sql`:
- Around line 1-2: The CREATE INDEX currently defined for
idx_vtxo_pubkey_updated_at on table vtxo will take a write lock on vtxo for the
duration of the operation; update the migration to create the index CONCURRENTLY
(i.e., use CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_vtxo_pubkey_updated_at ON
vtxo (pubkey, updated_at)) so writes are not blocked in production, and ensure
your migration runner does not wrap this statement in a transaction (or split it
out) since CONCURRENTLY cannot run inside a transaction block.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a8b64db2-83a1-4c9b-8962-bf11e0b35724

📥 Commits

Reviewing files that changed from the base of the PR and between bb633d8 and 832a065.

📒 Files selected for processing (4)

• internal/infrastructure/db/postgres/migration/20260318074150_vtxo_indexes.down.sql
• internal/infrastructure/db/postgres/migration/20260318074150_vtxo_indexes.up.sql
• internal/infrastructure/db/sqlite/migration/20260318074028_vtxo_indexes.down.sql
• internal/infrastructure/db/sqlite/migration/20260318074028_vtxo_indexes.up.sql