Question 1

How does writing into MongoDB work?

Accepted Answer

As a model sync with mapped document fields and paths rather than bulk table replication, since MongoDB is not available as a bulk sync destination. You decide the document shape and map BigQuery columns onto it, including nested paths. The collection can be created for you and arbitrary fields added, so the destination structure does not need to exist in full beforehand.

Question 2

Do nested BigQuery values survive?

Accepted Answer

They fit better here than in most destinations, because both sides model nesting properly. BigQuery reads records as objects and repeated fields as arrays, and those can be mapped onto document paths rather than being flattened into columns first. That makes this pairing a good fit when your warehouse model already has the nested shape the application wants, since nothing has to be taken apart and rebuilt.

Question 3

How are existing documents matched?

Accepted Answer

By the document identifier when you map one, which is the most reliable route, and serialized ObjectID values are converted rather than treated as plain strings. Without one, matching falls back to whichever destination field you nominated as the identity. Inserts and updates are grouped into bulk write calls rather than sent individually, and classification into insert or update work happens before the write.

Question 4

Is there anything to watch on types?

Accepted Answer

A few worth knowing. Datetimes are strictly coerced, so a malformed value becomes a record level error rather than being written as a string, which surfaces problem rows rather than hiding them. Beyond that, BigQuery structs arrive as nested objects and repeated fields as arrays, including arrays of records, which map onto document paths cleanly. JSON columns arrive as objects and BYTES as base64 encoded strings. NUMERIC and BIGNUMERIC come through as decimal values, though exact precision ultimately depends on what the destination can hold.

Connect BigQuery with MongoDB

Connect BigQuery and MongoDB with Polytomic

You define the document

Nested values fit naturally

Matches on document ID

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Connect BigQuery in Polytomic

Connect MongoDB in Polytomic

Create a sync between BigQuery and MongoDB

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