feat(root): add postgres best practices skill

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

Author: gracefullight

.agent/skills/postgres-best-practices/AGENTS.md

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+---
+name: supabase-postgres-best-practices
+description: Postgres performance optimization and best practices from Supabase. Use this skill when writing, reviewing, or optimizing Postgres queries, schema designs, or database configurations.
+license: MIT
+metadata:
+  author: supabase
+  version: "1.0.0"
+---
+
+# Supabase Postgres Best Practices
+
+Comprehensive performance optimization guide for Postgres, maintained by Supabase. Contains rules across 8 categories, prioritized by impact to guide automated query optimization and schema design.
+
+## When to Apply
+
+Reference these guidelines when:
+- Writing SQL queries or designing schemas
+- Implementing indexes or query optimization
+- Reviewing database performance issues
+- Configuring connection pooling or scaling
+- Optimizing for Postgres-specific features
+- Working with Row-Level Security (RLS)
+
+## Rule Categories by Priority
+
+| Priority | Category | Impact | Prefix |
+|----------|----------|--------|--------|
+| 1 | Query Performance | CRITICAL | `query-` |
+| 2 | Connection Management | CRITICAL | `conn-` |
+| 3 | Security & RLS | CRITICAL | `security-` |
+| 4 | Schema Design | HIGH | `schema-` |
+| 5 | Concurrency & Locking | MEDIUM-HIGH | `lock-` |
+| 6 | Data Access Patterns | MEDIUM | `data-` |
+| 7 | Monitoring & Diagnostics | LOW-MEDIUM | `monitor-` |
+| 8 | Advanced Features | LOW | `advanced-` |
+
+## How to Use
+
+Read individual rule files for detailed explanations and SQL examples:
+
+```
+rules/query-missing-indexes.md
+rules/schema-partial-indexes.md
+rules/_sections.md
+```
+
+Each rule file contains:
+- Brief explanation of why it matters
+- Incorrect SQL example with explanation
+- Correct SQL example with explanation
+- Optional EXPLAIN output or metrics
+- Additional context and references
+- Supabase-specific notes (when applicable)
+
+## Full Compiled Document
+
+For the complete guide with all rules expanded: `AGENTS.md`

.agent/skills/postgres-best-practices/SKILL.md

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+---
+title: Use tsvector for Full-Text Search
+impact: MEDIUM
+impactDescription: 100x faster than LIKE, with ranking support
+tags: full-text-search, tsvector, gin, search
+---
+
+## Use tsvector for Full-Text Search
+
+LIKE with wildcards can't use indexes. Full-text search with tsvector is orders of magnitude faster.
+
+**Incorrect (LIKE pattern matching):**
+
+```sql
+-- Cannot use index, scans all rows
+select * from articles where content like '%postgresql%';
+
+-- Case-insensitive makes it worse
+select * from articles where lower(content) like '%postgresql%';
+```
+
+**Correct (full-text search with tsvector):**
+
+```sql
+-- Add tsvector column and index
+alter table articles add column search_vector tsvector
+  generated always as (to_tsvector('english', coalesce(title,'') || ' ' || coalesce(content,''))) stored;
+
+create index articles_search_idx on articles using gin (search_vector);
+
+-- Fast full-text search
+select * from articles
+where search_vector @@ to_tsquery('english', 'postgresql & performance');
+
+-- With ranking
+select *, ts_rank(search_vector, query) as rank
+from articles, to_tsquery('english', 'postgresql') query
+where search_vector @@ query
+order by rank desc;
+```
+
+Search multiple terms:
+
+```sql
+-- AND: both terms required
+to_tsquery('postgresql & performance')
+
+-- OR: either term
+to_tsquery('postgresql | mysql')
+
+-- Prefix matching
+to_tsquery('post:*')
+```
+
+Reference: [Full Text Search](https://supabase.com/docs/guides/database/full-text-search)

.agent/skills/postgres-best-practices/rules/advanced-full-text-search.md

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+---
+title: Index JSONB Columns for Efficient Querying
+impact: MEDIUM
+impactDescription: 10-100x faster JSONB queries with proper indexing
+tags: jsonb, gin, indexes, json
+---
+
+## Index JSONB Columns for Efficient Querying
+
+JSONB queries without indexes scan the entire table. Use GIN indexes for containment queries.
+
+**Incorrect (no index on JSONB):**
+
+```sql
+create table products (
+  id bigint primary key,
+  attributes jsonb
+);
+
+-- Full table scan for every query
+select * from products where attributes @> '{"color": "red"}';
+select * from products where attributes->>'brand' = 'Nike';
+```
+
+**Correct (GIN index for JSONB):**
+
+```sql
+-- GIN index for containment operators (@>, ?, ?&, ?|)
+create index products_attrs_gin on products using gin (attributes);
+
+-- Now containment queries use the index
+select * from products where attributes @> '{"color": "red"}';
+
+-- For specific key lookups, use expression index
+create index products_brand_idx on products ((attributes->>'brand'));
+select * from products where attributes->>'brand' = 'Nike';
+```
+
+Choose the right operator class:
+
+```sql
+-- jsonb_ops (default): supports all operators, larger index
+create index idx1 on products using gin (attributes);
+
+-- jsonb_path_ops: only @> operator, but 2-3x smaller index
+create index idx2 on products using gin (attributes jsonb_path_ops);
+```
+
+Reference: [JSONB Indexes](https://www.postgresql.org/docs/current/datatype-json.html#JSON-INDEXING)

.agent/skills/postgres-best-practices/rules/advanced-jsonb-indexing.md

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+---
+title: Configure Idle Connection Timeouts
+impact: HIGH
+impactDescription: Reclaim 30-50% of connection slots from idle clients
+tags: connections, timeout, idle, resource-management
+---
+
+## Configure Idle Connection Timeouts
+
+Idle connections waste resources. Configure timeouts to automatically reclaim them.
+
+**Incorrect (connections held indefinitely):**
+
+```sql
+-- No timeout configured
+show idle_in_transaction_session_timeout;  -- 0 (disabled)
+
+-- Connections stay open forever, even when idle
+select pid, state, state_change, query
+from pg_stat_activity
+where state = 'idle in transaction';
+-- Shows transactions idle for hours, holding locks
+```
+
+**Correct (automatic cleanup of idle connections):**
+
+```sql
+-- Terminate connections idle in transaction after 30 seconds
+alter system set idle_in_transaction_session_timeout = '30s';
+
+-- Terminate completely idle connections after 10 minutes
+alter system set idle_session_timeout = '10min';
+
+-- Reload configuration
+select pg_reload_conf();
+```
+
+For pooled connections, configure at the pooler level:
+
+```ini
+# pgbouncer.ini
+server_idle_timeout = 60
+client_idle_timeout = 300
+```
+
+Reference: [Connection Timeouts](https://www.postgresql.org/docs/current/runtime-config-client.html#GUC-IDLE-IN-TRANSACTION-SESSION-TIMEOUT)

.agent/skills/postgres-best-practices/rules/conn-idle-timeout.md

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+---
+title: Set Appropriate Connection Limits
+impact: CRITICAL
+impactDescription: Prevent database crashes and memory exhaustion
+tags: connections, max-connections, limits, stability
+---
+
+## Set Appropriate Connection Limits
+
+Too many connections exhaust memory and degrade performance. Set limits based on available resources.
+
+**Incorrect (unlimited or excessive connections):**
+
+```sql
+-- Default max_connections = 100, but often increased blindly
+show max_connections;  -- 500 (way too high for 4GB RAM)
+
+-- Each connection uses 1-3MB RAM
+-- 500 connections * 2MB = 1GB just for connections!
+-- Out of memory errors under load
+```
+
+**Correct (calculate based on resources):**
+
+```sql
+-- Formula: max_connections = (RAM in MB / 5MB per connection) - reserved
+-- For 4GB RAM: (4096 / 5) - 10 = ~800 theoretical max
+-- But practically, 100-200 is better for query performance
+
+-- Recommended settings for 4GB RAM
+alter system set max_connections = 100;
+
+-- Also set work_mem appropriately
+-- work_mem * max_connections should not exceed 25% of RAM
+alter system set work_mem = '8MB';  -- 8MB * 100 = 800MB max
+```
+
+Monitor connection usage:
+
+```sql
+select count(*), state from pg_stat_activity group by state;
+```
+
+Reference: [Database Connections](https://supabase.com/docs/guides/platform/performance#connection-management)

.agent/skills/postgres-best-practices/rules/conn-limits.md

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+---
+title: Use Connection Pooling for All Applications
+impact: CRITICAL
+impactDescription: Handle 10-100x more concurrent users
+tags: connection-pooling, pgbouncer, performance, scalability
+---
+
+## Use Connection Pooling for All Applications
+
+Postgres connections are expensive (1-3MB RAM each). Without pooling, applications exhaust connections under load.
+
+**Incorrect (new connection per request):**
+
+```sql
+-- Each request creates a new connection
+-- Application code: db.connect() per request
+-- Result: 500 concurrent users = 500 connections = crashed database
+
+-- Check current connections
+select count(*) from pg_stat_activity;  -- 487 connections!
+```
+
+**Correct (connection pooling):**
+
+```sql
+-- Use a pooler like PgBouncer between app and database
+-- Application connects to pooler, pooler reuses a small pool to Postgres
+
+-- Configure pool_size based on: (CPU cores * 2) + spindle_count
+-- Example for 4 cores: pool_size = 10
+
+-- Result: 500 concurrent users share 10 actual connections
+select count(*) from pg_stat_activity;  -- 10 connections
+```
+
+Pool modes:
+
+- **Transaction mode**: connection returned after each transaction (best for most apps)
+- **Session mode**: connection held for entire session (needed for prepared statements, temp tables)
+
+Reference: [Connection Pooling](https://supabase.com/docs/guides/database/connecting-to-postgres#connection-pooler)

.agent/skills/postgres-best-practices/rules/conn-pooling.md

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+---
+title: Use Prepared Statements Correctly with Pooling
+impact: HIGH
+impactDescription: Avoid prepared statement conflicts in pooled environments
+tags: prepared-statements, connection-pooling, transaction-mode
+---
+
+## Use Prepared Statements Correctly with Pooling
+
+Prepared statements are tied to individual database connections. In transaction-mode pooling, connections are shared, causing conflicts.
+
+**Incorrect (named prepared statements with transaction pooling):**
+
+```sql
+-- Named prepared statement
+prepare get_user as select * from users where id = $1;
+
+-- In transaction mode pooling, next request may get different connection
+execute get_user(123);
+-- ERROR: prepared statement "get_user" does not exist
+```
+
+**Correct (use unnamed statements or session mode):**
+
+```sql
+-- Option 1: Use unnamed prepared statements (most ORMs do this automatically)
+-- The query is prepared and executed in a single protocol message
+
+-- Option 2: Deallocate after use in transaction mode
+prepare get_user as select * from users where id = $1;
+execute get_user(123);
+deallocate get_user;
+
+-- Option 3: Use session mode pooling (port 5432 vs 6543)
+-- Connection is held for entire session, prepared statements persist
+```
+
+Check your driver settings:
+
+```sql
+-- Many drivers use prepared statements by default
+-- Node.js pg: { prepare: false } to disable
+-- JDBC: prepareThreshold=0 to disable
+```
+
+Reference: [Prepared Statements with Pooling](https://supabase.com/docs/guides/database/connecting-to-postgres#connection-pool-modes)

.agent/skills/postgres-best-practices/rules/conn-prepared-statements.md

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+---
+title: Batch INSERT Statements for Bulk Data
+impact: MEDIUM
+impactDescription: 10-50x faster bulk inserts
+tags: batch, insert, bulk, performance, copy
+---
+
+## Batch INSERT Statements for Bulk Data
+
+Individual INSERT statements have high overhead. Batch multiple rows in single statements or use COPY.
+
+**Incorrect (individual inserts):**
+
+```sql
+-- Each insert is a separate transaction and round trip
+insert into events (user_id, action) values (1, 'click');
+insert into events (user_id, action) values (1, 'view');
+insert into events (user_id, action) values (2, 'click');
+-- ... 1000 more individual inserts
+
+-- 1000 inserts = 1000 round trips = slow
+```
+
+**Correct (batch insert):**
+
+```sql
+-- Multiple rows in single statement
+insert into events (user_id, action) values
+  (1, 'click'),
+  (1, 'view'),
+  (2, 'click'),
+  -- ... up to ~1000 rows per batch
+  (999, 'view');
+
+-- One round trip for 1000 rows
+```
+
+For large imports, use COPY:
+
+```sql
+-- COPY is fastest for bulk loading
+copy events (user_id, action, created_at)
+from '/path/to/data.csv'
+with (format csv, header true);
+
+-- Or from stdin in application
+copy events (user_id, action) from stdin with (format csv);
+1,click
+1,view
+2,click
+\.
+```
+
+Reference: [COPY](https://www.postgresql.org/docs/current/sql-copy.html)