Left Join performance on Spanner
Tomer Peled
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:
Tomer Peled
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/query-syntax#join-hints
JOIN@{JOIN_TYPE=APPLY_JOIN}
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