PostgreSQL production DDL

PostgreSQL Index Rollout Simulator

A useful index recommendation is not just CREATE INDEX. It needs rollout sequencing, lock expectations, WAL and replica risk, proof queries, and a clear abort line before touching production.

Review Question

Can this index be shipped without hurting writes, replicas, disk budget, or lock behavior more than the query improvement is worth?

At A Glance

Input
Query shape, table size, write rate, replicas, deploy window
Decision
Ship, defer, narrow predicate, or move to maintenance
Output
DDL, WAL budget, rollout runbook, abort criteria

What you get

  • CREATE INDEX statement with column order and partial predicate handling
  • Rollout risk score from table size, write rate, index count, and replica sensitivity
  • Production-safe validation SQL and pg_stat_progress_create_index checks
  • Abort criteria for lock waits, WAL growth, replica lag, and write latency

Guardrails

  • Models rollout risk before recommending production DDL.
  • Assumes index value must be proven against real query fingerprints.
  • Keeps write amplification and replica lag in the same review as read latency.

Signals covered

The page is designed to answer these production questions and search intents without losing the operational context.

index rolloutcreate index concurrently riskindex write amplificationindex deployment planindex validation sql
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How To Use It

Describe the query first. The index and the rollout plan update together.

This should answer three questions in one screen: which index shape is being proposed, why the columns are ordered that way, and how risky the first production rollout looks before live workload history starts to accumulate.

01

Map the query

Use the same WHERE, JOIN, ORDER BY, and partial predicate that appear in the real workload.

02

Price the rollout

Table size, writes, existing indexes, and replicas change whether an index is safe to ship.

03

Review the starters

Read the generated DDL, rollout notes, and starter checks before touching production.

Live Preview

Guarded rollout

This looks workable if you ship with monitoring, an explicit abort line, and proof that the query family really needs the index.

Candidate index
orders_account_id_status_customer_id_created_at_partial_idx
Build mode
INDEX CONCURRENTLY
WAL budget
98 GB
Replica watch
2 replicas to watch

1. Query Pattern

What does the query actually do?

Fill in the columns from the real query shape. Exact matches usually lead, then join keys, then range filters, then any leftover ORDER BY columns.

2. Production Context

What will production have to absorb?

The same index can be low risk on a quiet 10 GB table and dangerous on a 500 GB write-heavy table with replicas.

3. Deployment Guardrails

How do you want to ship it?

Pick the traffic window first, then decide whether this needs CONCURRENTLY or a planned maintenance slot.

What This Tool Can Settle Now

  • Whether the proposed column order matches the query shape you described.
  • Whether the build looks calm, watchful, or risky before you start it.
  • Which starter checks to keep visible during the first rollout pass.

What Still Needs Live Workload

  • Whether the index keeps helping after real traffic patterns change.
  • Whether write amplification, WAL, and replica lag stay acceptable over time.
  • Whether this index earns its storage and maintenance cost versus other options.

Starter Rollout Notes

  • >Confirm the query fingerprint really matches the predicates and sort order listed above.
  • >Rehearse CREATE INDEX CONCURRENTLY on production-like data with current statistics before touching the live table.
  • >Keep lock waits, pg_stat_progress_create_index, disk, and WAL visible while the build is running.
  • >Run ANALYZE after the build, then compare the same query shape again before keeping the index.

Watch During Build

  • !Replica replay lag stays above 30 seconds for longer than the rollout budget allows.
  • !Write latency or lock waits move outside the tolerated deployment window.
  • !Free disk cannot absorb the estimated 98 GB WAL and index build budget.

Starter Checks

Use these queries to start the rollout review. They help with the first pass, not the full historical verdict.

-- Track the index build while it is running.
SELECT pid, phase, lockers_total, lockers_done,
       blocks_total, blocks_done, tuples_total, tuples_done
FROM pg_stat_progress_create_index
WHERE relid = 'orders'::regclass;

-- Watch replica lag during the build.
SELECT application_name, state, write_lag, flush_lag, replay_lag
FROM pg_stat_replication;

-- Keep join predicates such as customer_id in the same query family when you re-run EXPLAIN.
-- Rerun the same query shape and verify the planner picks the new path.
EXPLAIN (ANALYZE, BUFFERS)
SELECT *
FROM orders
WHERE account_id = $1
  AND status = $2
  AND created_at >= $3
  AND deleted_at IS NULL
ORDER BY created_at DESC
LIMIT 50;

-- Refresh stats if the planner still behaves like the old table shape.
ANALYZE orders;

What Customers Need To Understand

This page should answer three production questions before anyone runsCREATE INDEX.

Customers do not need more index jargon. They need to know whether the proposed index matches the real query, whether production can absorb the rollout, and which checks prove it worked after deployment.

1. Is the index shape sensible?

Start with the query family, not the table. The proposal should line up with real WHERE, JOIN, ORDER BY, and partial predicate patterns.

2. Can production afford the rollout?

Reads are only half the story. Table size, write rate, existing indexes, replicas, and the deployment window decide whether this is routine or risky.

3. How do we prove it worked?

The rollout is not done when the DDL finishes. You still need EXPLAIN, query history, index usage, and replica health to prove the index earned its write cost.

Related PostgreSQL Hubs

PostgreSQL Slow Query Monitoring

Prioritize index work from slow queries that affect production.

PostgreSQL Query Optimizer

Planner estimates decide whether PostgreSQL uses the index.

PostgreSQL Query Monitoring

Watch whether the index is used after deployment.

Related Tools

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Useful here, still point-in-time.

This page should help with a real decision right now. It should not pretend to replace the historical evidence that production teams need after a deploy, during an incident, or across a longer rollout window.

Helpful On This Page

  • A candidate index shape based on the query pattern you entered
  • A rollout risk band from table size, writes, replicas, and timing
  • Starter checks to adapt before touching production

Still Needs Live History

  • Whether PostgreSQL actually uses the new index after deploy
  • How write latency, lag, and storage changed during the rollout
  • Whether the index kept earning its cost a week later
See Live History in MonPG