Convert PostgreSQL to MongoDB
A free online converter that translates PostgreSQL queries into MongoDB Aggregation. Paste your SQL, press Translate, and Query Studio rewrites the syntax that differs between the two databases — instantly, with no login and nothing stored.
Worth being clear about the trade: you are exchanging joins, enforced constraints and a rich type system for a flexible document model. If JSON handling is the motivation, PostgreSQL's JSONB may already do what you need.
PostgreSQL → MongoDB example
Here is a real PostgreSQL query and the MongoDB output Query Studio produces:
SELECT id, name, email
FROM users
WHERE active = 1 AND created_at > '2024-01-01'
ORDER BY created_at DESC
LIMIT 10;db.users.find({
$and: [
{
active: {
$eq: 1
}
},
{
created_at: {
$gt: "2024-01-01"
}
}
]
}, {
id: "$id",
name: "$name",
email: "$email"
}).sort({
created_at: -1
}).limit(10);What changes from PostgreSQL to MongoDB
- The SELECT becomes a MongoDB find() query or an aggregation pipeline.
- WHERE conditions turn into a $match / filter document.
- JOIN becomes a $lookup stage, and GROUP BY becomes $group.
- ORDER BY and LIMIT become $sort and $limit — computed deterministically, no AI.
PostgreSQL to MongoDB: what actually catches people out
Syntax is the part a translator can fix. These are the differences that survive a clean conversion and show up later as wrong results rather than as errors.
You are giving up the things Postgres is best at
Joins with a real optimiser, transactional integrity across tables, constraints the database enforces, and a rich type system. If the reason for moving is JSON handling, note that PostgreSQL's JSONB is genuinely good — indexable with GIN, queryable with operators, and transactional — so the move may not buy what it appears to.
JSONB queries do not translate to MongoDB queries
They look similar and are not. Postgres's @> containment operator on JSONB and MongoDB's nested field queries have different semantics for arrays and different index requirements. Anything doing real JSONB work needs rewriting rather than converting.
Aggregation pipelines are ordered, and the order is the performance
GROUP BY becomes $group, WHERE becomes $match, ORDER BY becomes $sort. What SQL leaves to the planner, a pipeline makes explicit: a $match after a $group cannot use an index, where the same predicate before it can. The translation preserves meaning; it cannot make the ordering decisions a planner would.
Arrays finally have somewhere natural to go
This is the one place the migration is a genuine simplification. A Postgres TEXT[] maps directly onto a MongoDB array field, with indexing and query operators that treat it as a first-class thing.
What this converter will not do
Query Studio translates SQL syntax. Being honest about the boundary is more useful than claiming there isn’t one — and on PostgreSQL → MongoDB specifically, these are the three that matter most:
Transaction and isolation semantics
Default isolation levels, locking behaviour and whether DDL is transactional all vary. Two engines can run identical SQL and disagree about what is visible to a concurrent reader.
Stored procedures, functions and triggers
Procedural code — PL/pgSQL, T-SQL procedures, MySQL routines — is a different language in every engine, with different control flow, error handling, variable declaration and transaction semantics. Query Studio translates queries, not programs. These have to be ported by hand.
Performance characteristics
A converted query is correct, not fast. Index strategy, partitioning, distribution keys and statistics differ per engine, and a query that was well-tuned for the source is merely valid on the target. Run the Analyze and Optimize tabs on the output.
The full list of what a syntax translator cannot do is on the Query Studio page.
How to convert PostgreSQL to MongoDB
- Open the Query Studio editor and choose PostgreSQL as the “From” dialect.
- Choose MongoDB as the “To” dialect.
- Paste your PostgreSQL query and press Translate — copy the MongoDB result.
Try it with your own query
The editor is preloaded with PostgreSQL → MongoDB. You can also explain, format, validate and analyze the result.
Convert PostgreSQL to MongoDB now →Working with the data rather than the schema? Open a large CSV, JSON or Parquet file and query it with SQL — no upload, no row limit, and files far past what Excel will open.
PostgreSQL to MongoDB FAQ
Is this PostgreSQL to MongoDB converter free?
Yes — it's completely free with no account, no sign-up and no usage limits. Your query is processed to return the result and never stored.
Is the PostgreSQL to MongoDB conversion accurate?
Query Studio rewrites syntax deterministically using real SQL parsers, so it gives the same result every time — there is no AI involved and no variation between runs. It handles the differences listed above automatically. What it cannot do is anything semantic: stored procedures, triggers, vendor extensions and performance characteristics all need a human. Review complex, vendor-specific queries before running them in production.
What breaks when migrating from PostgreSQL to MongoDB?
The differences that most often cause problems on this pair: You are giving up the things Postgres is best at; JSONB queries do not translate to MongoDB queries; Aggregation pipelines are ordered, and the order is the performance; Arrays finally have somewhere natural to go. Each is explained in full above, with before-and-after examples where seeing it is quicker than reading about it.
Does this PostgreSQL to MongoDB converter use AI?
No. Every result is computed by real SQL parsers and rule engines, which is what makes it free, instant, unlimited and identical on every run. Nothing is sent to a model, so there are no rate limits, no per-request cost to pass on, and no possibility of a confidently wrong answer that looks plausible.