MongoDB

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Quick setup

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Connection settings

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Connection URL

mongodb://user:password@host:27017/database?authSource=admin
mongodb+srv://user:password@cluster.mongodb.net/database

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MongoDB Atlas (SRV)

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Replica sets

mongodb://user:pass@host1:27017,host2:27017,host3:27017/db?replicaSet=rs0

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Browsing collections

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Views

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Indexes

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Missing fields and null

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Binary UUIDs

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Creating a collection

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Inserting documents

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Editing documents

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Renaming and removing fields

db.people.updateMany({"status": {"$exists": true}, "state": {"$exists": false}}, {"$rename": {"status": "state"}})
db.people.updateMany({"tmp": {"$exists": true}}, {"$unset": {"tmp": ""}})

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Writing queries

db.orders.find({status: "completed"}, {customerId: 1, total: 1})
  .sort({date: -1})
  .limit(20)

db.sales.aggregate([
  {$match: {date: {$gte: ISODate("2025-01-01")}}},
  {$group: {_id: "$product", totalSales: {$sum: "$amount"}}}
])

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Scripts

var stale = [];
db.orders.find({status: "pending"}).forEach(function (order) {
  if (order.updatedAt < ISODate("2025-01-01")) { stale.push(order._id); }
});
print("stale orders: " + stale.length);

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Values

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Collection references

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Cursors

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Write options

db.users.updateOne({_id: 1}, {$set: {active: true}}, {upsert: true})
db.events.insertMany(batch, {ordered: false, writeConcern: {w: "majority"}})

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When a write stops part-way

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Methods

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SSL/TLS

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Limitations

• A row with no _id cannot be updated or deleted. The save is refused rather than matched on the remaining fields, and every change stays pending. Keep _id in the projection so every row carries one.
• A binary value keeps the subtype it was read with. Bytes typed into a new row are saved as subtype 0 where the validator declares the field binData.
• Other bytes refuse the save when their subtype was never read, or was read as two different ones: bytes typed into an existing document, pasted from another collection, or put back by Data Rewind after TablePro restarts. Write that value with a query.
• A field holding text in some documents and objects or arrays in others takes no value that reads as JSON from the grid, since it could be either type: the save is refused. Write it with a query.
• A new row, duplicate or paste cannot hold a field named __proto__, or an empty field name at any depth: the save is refused. Use Remove Field on that cell, save, then set it on the saved document.
• _id is read-only in the grid, the row inspector and Edit Document…, and a row added with Add Row is inserted without one so the server generates it. To choose your own, use Insert Document….
• Edit Document… opens a message instead of the text for a document it cannot write back exactly: a top-level field starting with $, a repeated field name, a subdocument shaped like {"$numberInt": "5"}, more than 28 levels of nesting, or a guarded save over 16 MB, which a document made mostly of numbers reaches at about 5 MB. Change such a document with updateOne in a query tab.
• The server replaces a top-level Timestamp(0, 0) with the current time whenever a whole document is written, so Insert Document… stores the time there and Edit Document… refuses a document holding one. $set in a query tab keeps it.
• Edit Document… also refuses a document holding a NaN, double or decimal, or JavaScript code with a scope. Change such a document with updateOne in a query tab.
• Edit Document… needs MongoDB 4.0 or later, and refuses a view and a time-series collection. Edit the collection a view reads, and change time-series documents with updateMany in a query tab.
• In a collection whose default collation is not simple, saving a document with a string _id reads the whole collection to find it. On a large collection, change the document with updateOne in a query tab instead.
• Transactions are not exposed. Statements always run standalone, on any topology.
• A collection takes one text index. A second FULLTEXT row fails after the collection and the indexes before it are created: list every text field in one index instead.
• New Table… writes the validator with the server’s own level and action. To log bad documents instead of refusing them, run db.runCommand({collMod: "articles", validationAction: "warn"}) after creating the collection.
• Nested paths filter but do not sort. Sorting works on the grid’s own columns.
• Filtering, sorting or editing a field named "" or starting with $ fails in the grid. A dotted name such as a.b reads as the path to b inside a. Use $getField and $setField in the query editor.
• same element covers a field one array deep. A path through an array inside another array needs nested $elemMatch, so those filter with dot notation only.
• GridFS buckets are not browsable, and change streams are unsupported.
• A Code scope holding an object that opens with $type, $regex or $options, such as Code("f", {a: {$type: "binData"}}), fails with This is not a document MongoDB can read. List another key of that object first.
• A script that loops without touching the database cannot be stopped: JavaScriptCore has no public way to interrupt one. Cmd+. stops anything that reads, writes or prints, which covers every query. A script silent for 120 seconds is abandoned and the shell restarts.
• Field names that are whole numbers up to 4294967294 ("0", "12") sort ahead of the rest in a document literal, which is what JavaScript does with them. A nested object with such a key after another key, or with a key named __proto__, refuses the save when it is duplicated or written whole. Use Insert Document… or a query for it.
• Decimal128("…") with more than 34 significant digits, or an exponent outside the decimal128 range, fails when the statement runs with “This is not a document MongoDB can read”. Round a long value to 34 digits. For an exponent out of range, store the value scaled to a unit that fits, or as a double or a string.
• An MQL export of a view holds the view’s documents, not the view, so restoring the file creates a collection of that name. Drop that collection and run the view’s Show DDL text to get the view back.
• A time-series collection takes inserts and deletes from the grid, but refuses an edited cell and a rename, and the server’s error is shown. Change its documents from a query tab with updateMany filtered on the meta field.
• A filter or validator with a regular expression under $regex, such as {email: {$regex: /@/i}}, is refused as a document MongoDB cannot read. Write {email: /@/i} or {email: {$regex: "@", $options: "i"}} instead. Show DDL writes such a validator the way the server holds it, which runs in mongosh but not in a query tab.
• A DBPointer, an undefined, or a date more than 100 million days from 1 January 1970 has no mongosh spelling, so Show DDL keeps its Extended JSON wrapper. A query tab runs that text; mongosh does not.
• bulkWrite runs its operations in order and stops at the first one that fails, even with ordered: false. To go on past a failed insert, use insertMany with ordered: false.
• A field rename checks indexes, search indexes, validators and views in the same database only. Other databases and application code keep the old name: update them after the rename.
• A field rename does not lock the collection. A validator another client sets in the milliseconds between the last check and the save’s collMod is replaced by it.
• MongoDB before 4.4 cannot measure a document, so a rename to a longer name is not checked against the 16 MB limit there. Rename to a name no longer than the old one on those servers when documents are close to the limit.
• Compare & Sync compares MongoDB structures but writes no script for them, because a collection’s fields come from a sample of its documents.

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Troubleshooting