PostgreSQL Rails Analyzer

Analyze Rails applications for PostgreSQL performance issues and provide actionable optimization recommendations based on "High Performance PostgreSQL for Rails" best practices.

Analysis Scripts

Run from the Rails application root directory:

1. N+1 Query Analysis

ruby scripts/analyze_n_plus_one.rb

Detects potential N+1 query issues by analyzing:

Controller actions for queries without eager loading
View files for association access patterns
Missing includes, preload, or eager_load calls

2. Index Analysis

ruby scripts/analyze_indexes.rb

Identifies indexing opportunities:

Foreign keys without indexes (critical)
Boolean columns that could benefit from partial indexes
Columns frequently used in WHERE clauses
Missing composite indexes

3. Configuration Analysis

ruby scripts/analyze_config.rb

Reviews database.yml for:

Connection pool sizing
Timeout configurations (statement_timeout, lock_timeout)
Prepared statements settings
SSL/TLS configuration
Connection reaping configuration
Recommended PostgreSQL extensions

Workflow

Step 1: Understand the Request

Clarify what the user wants to analyze: full performance audit, specific issue (slow queries, N+1 problems), configuration review, or schema optimization.

Step 2: Run Appropriate Analysis Scripts

# For comprehensive analysis, run all three
ruby scripts/analyze_n_plus_one.rb
ruby scripts/analyze_indexes.rb
ruby scripts/analyze_config.rb

Step 3: Review Results

Script output categorizes issues by severity:

WARNING: High-priority issues that likely impact performance
INFO: Optimization opportunities and best practice recommendations

Step 4: Provide Recommendations

Create a prioritized list of actionable recommendations:

Critical Issues (fix immediately) — FK indexes, N+1 in hot paths, missing timeouts
Performance Optimizations (high impact) — partial indexes, counter caches, eager loading
Best Practices (preventative) — configuration tuning, pool optimization, monitoring

Step 5: Generate Migration Code

For index and schema recommendations, provide ready-to-use migration code. Use algorithm: :concurrently for production migrations to avoid locking tables.

class AddPerformanceIndexes < ActiveRecord::Migration[7.0]
  disable_ddl_transaction!

  def change
    add_index :posts, :user_id, algorithm: :concurrently
    add_index :users, :active, where: "active = false", algorithm: :concurrently
    add_index :orders, [:status, :created_at], algorithm: :concurrently
  end
end

Step 6: Reference Additional Documentation

Load these references when users need deeper understanding:

references/performance_guide.md — comprehensive best practices (indexes, queries, config, schema design, monitoring)
references/anti_patterns.md — 25 common mistakes organized by category (queries, indexes, schema, config, transactions)

Advanced Analysis

For deeper analysis beyond the scripts, manually review:

Schema Design — data types (bigint for high-volume PKs, jsonb vs json), constraints (NOT NULL, CHECK, FOREIGN KEY)
Query Patterns — use rails c to run EXPLAIN ANALYZE on slow queries, check for sequential scans on large tables
Model Code — missing counter caches, batch operation opportunities (find_each instead of each)

Limitations

These analysis scripts use static analysis. They may produce false positives (flagging non-issues) or false negatives (missing runtime-only issues). Always recommend testing fixes in staging and using EXPLAIN ANALYZE to verify.

Complementary Tools

Suggest for ongoing monitoring: PgHero (dashboard), pg_stat_statements (query stats), Bullet gem (runtime N+1 detection), Rails query logging (development visibility).

postgresql-rails-analyzer