perf: add query-aligned indexes for Login model (timestamp desc, country upper, ip)

[nishantxscooby]

🎯 Problem Statement

Fixes #494 (Part 1: Login Model Indexes)

BuffaLogs has performance issues due to missing database indexes on the Login model. Queries using timestamp, country, and ip fields are performing full table scans, causing:

• Slow query execution (especially with ORDER BY -timestamp)
• High database CPU usage under normal load
• Poor scalability as data grows beyond 100k+ records

🔍 Solution

Added 3 query-aligned indexes to the Login model based on comprehensive codebase analysis:

1. Descending Timestamp Index

models.Index(fields=["-timestamp"], name="login_timestamp_desc_idx")

• Query Pattern: Login.objects.filter(...).order_by("-timestamp") (used in 10+ locations)
• Files: models.py:76, dashboards/charts.py, views/logins.py:25
• Impact: Optimizes descending time-based sorting

2. Functional Country Index (Case-Insensitive)

models.Index(Upper("country"), name="login_country_upper_idx")

• Query Pattern: Login.objects.filter(country__iexact=...) (used in 8+ locations)
• Files: models.py:89, detection.py:138, dashboards/charts.py
• Impact: Supports case-insensitive country lookups without full table scans

3. IP Address Index

models.Index(fields=["ip"], name="login_ip_idx")

• Query Pattern: Login.objects.filter(ip=...) (exact matches)
• Files: models.py:81, detection queries
• Impact: Fast IP-based filtering

✅ Verification

Database Indexes Created:

-- Verified with: SELECT * FROM pg_indexes WHERE tablename = 'impossible_travel_login';

login_timestamp_desc_idx | CREATE INDEX login_timestamp_desc_idx ON impossible_travel_login (timestamp DESC)
login_country_upper_idx  | CREATE INDEX login_country_upper_idx ON impossible_travel_login (UPPER(country))
login_ip_idx             | CREATE INDEX login_ip_idx ON impossible_travel_login (ip)

Query Performance (EXPLAIN ANALYZE):

Test 1: Timestamp Descending

EXPLAIN ANALYZE SELECT * FROM impossible_travel_login 
ORDER BY timestamp DESC LIMIT 10;

-- Result: Index Scan using login_timestamp_desc_idx
-- Execution Time: 0.065 ms

Test 2: Country Case-Insensitive

EXPLAIN ANALYZE SELECT * FROM impossible_travel_login 
WHERE UPPER(country) = UPPER('italy');

-- Result: Bitmap Index Scan on login_country_upper_idx
-- Execution Time: 0.080 ms

Test 3: IP Exact Match

EXPLAIN ANALYZE SELECT * FROM impossible_travel_login 
WHERE ip = '192.168.1.1';

-- Result: Index Scan using login_ip_idx
-- Execution Time: 0.015 ms

📋 What Was NOT Done (Per Maintainer Requirements)

Based on feedback from @Lorygold on PRs #524, #531, #540:

• ❌ index field - Skipped (low entropy, per Perf: add missing indexes for Login filters to avoid sequential scans #524)
• ❌ event_id field - Skipped (only used in tests, per perf: add indexes for Login filter fields #540)
• ❌ user_agent field - Skipped (large text field, minimal benefit)
• ❌ Alert model indexes - Separate issue (requires JSON field optimization)
• ❌ Code reformatting - Only modified Login Meta class, no Black/isort on entire file

🔬 Testing

• Migration generated and applied successfully
• All 3 indexes created in PostgreSQL
• EXPLAIN ANALYZE confirms index usage (0.015-0.080ms)
• 276 unit tests pass (0 failures related to this change)
• No linter errors (models.py was already non-compliant on develop branch)
• Comprehensive query analysis across entire codebase

📚 References

• Codebase Analysis: Analyzed 100+ Login.objects queries across models, views, dashboards, charts
• Django Docs: Model Meta indexes
• Functional Indexes: Django 5.x Upper() functional indexes

📝 Migration Details

File: 0023_login_login_timestamp_desc_idx_and_more.py
Operations:

1. AddIndex on -timestamp (descending order)
2. AddIndex on Upper(country) (case-insensitive functional index)
3. AddIndex on ip (standard B-tree)

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Note: This PR addresses Login model performance only. Alert model optimization (mentioned in #494) requires a different approach due to JSON field queries and should be handled in a separate PR.

[nishantxscooby]

@Lorygold Could you please review this when you have a chance?

This PR addresses Part 1 of issue #494 (Login model indexes). I've added 3 query-aligned indexes based on comprehensive codebase analysis:

1. Descending timestamp index - for order_by("-timestamp") queries (used in 10+ locations)
2. Functional country index - for country__iexact lookups (case-insensitive)
3. IP address index - for exact IP filtering

I followed your feedback from #524, #531, and #540 - skipping low-value fields like index and event_id.

All 276 tests pass, and EXPLAIN ANALYZE confirms the indexes are being used (0.015-0.080ms query times).

Thanks! 🙏

[Lorygold]

For next times: it's not necessary to open new PRs, you can work on the initial one and update it.
So, you can close the old PR: #540

Btw, now it's okay, thank you!

@lucaCigarini @eugenioseveri I think this PR can be merged