CODEWITHSUNDEEP
google-cloud-platformgoogle-cloud-spanner
Tomer Peled
Tomer Peled

Reputation: 3591

Left Join performance on Spanner

We encountered with a disturbing issue. Seems that when we are using left join on the Google Spanner it suffers from bad performance.

The left join operator cause to full scan on the right tables rows from some reason...

Anyone else encountered with this? Of course that when we're removing the left join operator and just using inner join the performance is good...

Execution Plan:

enter image description here

Upvotes: 2

Views: 1963

Answers (1)

Tomer Peled
Tomer Peled

Reputation: 3591

So, it appears that we needed to tell the Google Spanner how to conduct the join operation. In our case APPLY_JOIN did the trick: https://cloud.google.com/spanner/docs/reference/standard-sql/query-syntax#join_hints

JOIN@{JOIN_TYPE=APPLY_JOIN}

Upvotes: 2

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