Writes and atomic operations

Distinguish insert from save

insertSuspending(entity) delegates a new-document insert. An existing ID can produce a duplicate-key failure. saveSuspending(entity) can insert or replace a document according to its ID state.

val inserted = mongoOperations.insertSuspending(
    User(name = "Alice", email = "alice@example.com", age = 30, city = "Seoul")
)

val saved = mongoOperations.saveSuspending(inserted.copy(city = "Suwon"))

When only a few fields change, use a conditional update rather than rewriting the whole document with save.

Read UpdateResult

updateFirstSuspending, updateMultiSuspending, and upsertSuspending return UpdateResult.

val result = mongoOperations.updateFirstSuspending<User>(
    queryOf("email".criteria() eq "alice@example.com"),
    ("city" setTo "Suwon").andInc("loginCount", 1),
)

check(result.matchedCount == 1L)

A matchedCount of zero means no document matched. A matched document with modifiedCount == 0 may already contain the requested value or may not be counted as changed by the server. Do not treat those states as identical.

Upsert

upsertSuspending updates a matching document and inserts one when none matches. Ensure that the query contains a stable business key so a repeated request does not create more documents. Back a required invariant with a unique index.

Atomic modify and remove

findAndModifySuspending and findAndRemoveSuspending ask the server to modify or remove one matching document atomically and return the document. No match returns null.

val previous: User? = mongoOperations.findAndModifySuspending(
    queryOf("email".criteria() eq email),
    "loginCount" incBy 1,
)

The default find-and-modify operation returns the document before modification. This extension has no options parameter; use Spring Data’s options-capable API directly when the updated document is required.

Delete results and transactions

Deleting by query or entity returns DeleteResult. Compare deletedCount with the expected count. The extension does not start a transaction, so group a business operation that touches multiple collections in a Spring reactive transaction at the service boundary.

Source and tests

• ReactiveMongoOperationsCoroutines.kt
• ReactiveMongoOperationsCoroutinesTest.kt
• UpdateExtensions.kt

Next chapter

Build write filters and update documents in Criteria, Query, and Update DSL.