Question 1

What can I sync out of BigQuery?

Accepted Answer

Tables and views across your datasets, or a custom SQL query as a model source, which is the more common choice when the shape you want in MySQL differs from the warehouse table. Polytomic runs a query job and reads the results through the BigQuery Storage Read API where it is available, falling back to REST transparently for cases it cannot serve, such as external tables or materialized views. Nested values arrive as objects and repeated fields as arrays.

Question 2

What happens to nested BigQuery values?

Accepted Answer

They come out of BigQuery as structured values, records as objects and repeated fields as arrays, so the question is how you want them to land. Flattening in the model, by selecting the specific fields you want as scalar columns, usually gives the cleanest MySQL table. If you would rather keep them whole, write them into a JSON column and query with MySQL's JSON functions. NUMERIC and BIGNUMERIC keep their precision where the destination type allows.

Question 3

Does the MySQL table need a primary key?

Accepted Answer

Not for a model sync. You map an identity field from BigQuery onto a destination column and updates match on it, whether or not MySQL has a key declared there. Uniqueness still matters, since a non unique identity will update every matching row. Bulk table replication behaves differently: with a primary key it merges on that key, and without one the table is recreated or truncated and reloaded.

Question 4

What drives cost on a frequent schedule?

Accepted Answer

Bytes scanned in BigQuery, multiplied by how often the sync runs. The levers are all on the read side. Set a tracking field, which incremental reads require along with a unique identity on the table, and partition and ideally cluster the source so the tracking predicate prunes rather than sweeping history. Select only the columns you map, and be wary of views or custom SQL that stop partitions being pruned. Those together usually turn an expensive sync into a cheap one without changing what lands in MySQL.

Connect BigQuery with MySQL

Connect BigQuery and MySQL with Polytomic

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