Expose calculate_token #658
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Helps (or arguably fixes) scylladb#468 For smarter batch constitution (following up on scylladb#448), it is required to have access to the token a particular statement would be directed to. However, that is pretty difficult to do without access to calculate_token. That was initially put in scylladb#508, but planned to put in a separate pr to keep it minimal (scylladb#508 (comment)) It seems I had forgotten to open that separate PR, and I end up getting bitten by that now that I want to constitute my batches in a smarter way. So here it is. I'm only putting "helps" above because I think we may want to also expose query planning ( `session.plan(prepared_statement, serialized_values) -> impl Iterator<Item = (Arc<Node>, ShardID)>` ) as that may make it significantly easier - but I'd like to keep this PR that just *enables* the ideal behavior as simple as possible.
piodul
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Mar 20, 2023
Ten0
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Resolves scylladb#468 This is a follow-up on scylladb#508 and scylladb#658: - To minimize CPU usage related to network operations when inserting a very large number of lines, it is relevant to batch. - To batch in the most efficient manner, these batches have to be shard-aware. Since scylladb#508, `batch` will pick the shard of the first statement to send the query to. However it is left to the user to constitute the batches in such a way that the target shard is the same for all the elements of the batch. - This was made *possible* by scylladb#658, but it was still very boilerplate-ish. I was waiting for scylladb#612 to be merged (amazing work btw! 😃) to implement a more direct and factored API (as that would use it). - This new ~`Session::first_shard_for_statement(self, &PreparedStatement, &SerializedValues) -> Option<(Node, Option<Shard>)>` makes shard-aware batching easy on the users, by providing access to the first node and shard of the query plan.
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Helps (or arguably fixes) #468
For smarter batch constitution (following up on #448), it is required to have access to the token a particular statement would be directed to. However, that is pretty difficult to do without access to calculate_token.
That was initially put in #508, but planned to put in a separate PR to keep it minimal
(#508 (comment))
It seems I had forgotten to open that separate PR, and I end up getting bitten by that now that I want to constitute my batches in a smarter way. ^^'
So here it is.
I'm only putting "helps" above because I think we may want to also expose query planning (
session.plan(prepared_statement, serialized_values) -> impl Iterator<Item = (Arc<Node>, ShardID)>) as that may make it significantly easier on the user to obtain the relevant keys for batching - but I'd like to keep this PR that just enables the ideal behavior as simple as possible.Pre-review checklist
Fixes:annotations to PR description.