Query BigQuery table partitioned by Partitioning Field

Question

We can create a table partitioned by Partitioning Field. Doc Reference here.

I created a table visitors that contains 2 fields:

• visitor: STRING
• part: TIMESTAMP <-- this is the Partitioning Field

When I query the table:

SELECT * FROM mydataset.visitors WHERE part >= "2018-03-14 09:00:00" AND part < "2018-03-15 18:00:00"

Questions:

• Is the BigQuery engine smart enough to scan only the 2 partitions 2018-03-14 and 2018-03-15, then find all rows that satisfy the hour range?
• Or does BigQUery do a full scan of all partitions?

Thanks

Answer 1

The whole point of partitioned tables, is that BigQuery only has to scan the partitions referenced in your where clause. You can easily see this by removing the where clause and you'll see the amount of data to be processed increase (in the UI). To answer your question, yes, it's smart enough ;-)