feat: pipeline

[cesco69]

This PR implements pipeline mode, allowing multiple queries to be sent to the PostgreSQL server without waiting for the results of previous queries. This significantly reduces network latency, especially for batch operations or high-latency connections.

Usage

const { Client, Pool } = require('pg')

// Enable pipeline mode on Client
const client = new Client({ pipelineMode: true }) 
await client.connect()

// All queries are sent immediately without waiting
const [r1, r2, r3] = await Promise.all([
  client.query('SELECT 1'),
  client.query('SELECT 2'),
  client.query('SELECT 3'),
])

// Also works with Pool
const pool = new Pool({ pipelineMode: true })

Features

• Opt-in via configuration: Enable with pipelineMode: true (default: false)
• Error isolation: Failed queries don't affect other queries in the pipeline
• Transaction support: BEGIN/COMMIT/ROLLBACK work normally
• Prepared statements: Full support, including concurrent queries with the same statement name

Restrictions

• No multi-statement queries: Queries containing multiple SQL statements separated by ; are rejected with a descriptive error (see postgresql)
• No COPY operations: COPY commands are not supported in pipeline mode (see postgresql)
• JavaScript client only: Not available in pg-native, would require:
  • feat: pipeline node-libpq#118
  • feat(pg-native): pipeline (WIP) #3592)

Related Issues

• Closes implement pipelining mode allowed by libpq 14 #2646