query-tab.md

Query tab

Purpose

In a collection's tab the user writes a filter in MongoDB shell syntax, e.g. { age: { $gt: 18 }, _id: ObjectId("…") }, runs it and sees the matching documents. This is how Monolens reads data today.

How it works

The view (TabViewQuery)

• A query input, an Execute button, a limit dropdown (10, 25, 50, 100, 200; default 50), a Refresh button and the switch between table and JSON view.
• When the view mounts it runs the query once. Execute, Refresh and Ctrl+Enter run it again.
• execute():
  1. An empty input becomes {}.
  2. parseMongoDbQuery parses the input. A parse error is a toast, and nothing is sent.
  3. It invokes start_find_documents with the active connection, the tab's database and collection, the filter, skip: 0 and the limit, then await_task_result.
  4. It stores { documents, totalCount }.
  5. If documents came back, it takes the field names of the first one for the autocomplete.
• The documents go to the table or the JSON view, see document-views.md.

The query input (QueryInput)

• A CodeMirror 6 editor, kept to one line, with the One Dark theme. A clear button (X) appears when the query is not empty and resets it to { }.
• Autocomplete (useMongoAutoComplete in src/domains/mongo):
  • After a colon it offers the query operators ($eq … $text) and the shell functions (ObjectId, ISODate, NumberLong, NumberDecimal, Timestamp, RegExp), which insert their parentheses.
  • After { or , it offers the field names of the last result, the top-level operators $and, $or, $nor, $text, and the operators.

The parser (src/utils/queryParser)

• generateTokens turns the text into tokens: braces, brackets, parentheses, colon, comma, strings in " or ' with backslash escapes, numbers (digits, ., a leading -), and identifiers ([a-zA-Z_$][a-zA-Z0-9_$]*).

• createParser().parseValue() reads objects, arrays, strings, numbers, true, false, null and function calls. Keys may be identifiers or strings. A trailing comma is allowed.

• A function call becomes extended JSON (transformFunction):

  Shell	Sent as
  ObjectId("x")	{ $oid: "x" }
  ISODate("x"), Date("x")	{ $date: "x" }
  NumberLong(n)	{ $numberLong: "n" }
  NumberDecimal(n)	{ $numberDecimal: "n" }
  Timestamp(t, i)	{ $timestamp: { t, i } }
  BinData(type, "b64")	{ $binary: { base64, subType: type } }
  RegExp("p", "o")	{ $regex: "p", $options: "o" }

  Any other function is an error.

In Rust (find_documents of the MongoDB driver)

• bson::to_document turns the JSON filter into BSON. bson's serializer reads objects that look like extended JSON as BSON types, so { $oid }, { $numberLong }, { $numberDecimal }, { $timestamp } and { $date } with an RFC 3339 string become real types.
• find with skip, limit and allowDiskUse(true). The cursor is read into a list of JSON values.
• count_documents with the same filter gives totalCount.

Decisions

• A parser of our own (0c738f1) for the shell syntax: unquoted keys, single quotes and shell functions, which JSON doesn't allow. The history gives no reason for not using a library.
• Extended JSON as the format between UI and Rust. The filter crosses IPC as JSON, and bson turns the extended-JSON objects into types without code of our own.
• CodeMirror with autocomplete (9f677e1).
• Run on open: a new tab shows the first documents at once.

Building steps

Date	Step	Commit
2026-02-23	start_find_documents with filter, skip and limit, as a task	cbc9b83
2026-02-24	TabViewQuery, proof of concept	e0256f3
2026-02-25	First display of the documents	8722010
2026-02-26	Query parser with tests, JSON view	0c738f1
2026-03-01	CodeMirror query input with autocomplete	9f677e1
2026-03-02	Header and query controls stay in place while the data scrolls	0a88369
2026-03-02	Clear button	17ac29b
2026-03-02	Table view, limit dropdown, view switch	ead8967

Limits and open points

Read from the code on 2026-11-03, not reproduced in the running app:

• Only filter and limit. skip is always 0, so there is no paging. Projection and sort are missing too, although issue #12 (closed) listed them. The Rust command already takes skip.
• totalCount is computed but never shown. Every query also counts all matches, a second full query on the server.
• Server errors are swallowed. execute() has try/finally without catch: a failed query shows no toast, the old results stay, and the rejection is unhandled. It also bypasses ConnectionServiceIPC.findDocuments and abortableInvoke, so it can't be cancelled and its error isn't unwrapped.
• The autocomplete knows only the first document's fields. new Set(...arrays) uses only its first argument.
• Shell functions that don't become BSON types stay plain objects and match nothing, without an error:
  • ISODate("2024-01-01"): bson only reads a full RFC 3339 string like 2024-01-01T00:00:00Z as a date
  • ObjectId with a string that is not 24 hex characters
  • BinData(0, "…"): bson expects the subtype as a hex string
• RegExp becomes the $regex operator, which works as the condition of a field but not inside $in.
• Not supported: dotted keys without quotes (user.name: 1 fails; "user.name": 1 works), /regex/ literals, new Date(), NumberInt, UUID, exponents (1e5), comments.
• Text after the first complete value is ignored: { a: 1 } } runs as { a: 1 }.
• ConnectionServiceIPC.findDocuments exists and is unused.
• The test named "throws" in query-parser.test.ts checks nothing: it parses { a: 1, }, which succeeds.
• Open issues: #11 a query builder, #41 building queries by drag and drop, #13 export a query as code, #42 Ctrl+Enter runs in every tab.

Where the code is

What	Path
View	src/components/tabs/views/TabViewQuery.vue
Input and autocomplete	src/components/query/QueryInput.vue, src/domains/mongo/index.ts
Parser and tests	src/utils/queryParser/, src/utils/queryParser/test/
Command	src-tauri/src/database/commands/start_find_documents.rs
Find and count	find_documents in src-tauri/src/drivers/mongo_official_driver.rs, src-tauri/src/database/models/find_document.rs