[sql_server] Refactor CdcStream::into_stream to better stream changes
#32159
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…stead of collecting in memory
martykulma
approved these changes
Apr 10, 2025
src/sql-server-util/src/lib.rs
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| pub fn query_streaming<'q>( | ||
| &mut self, | ||
| query: impl Into<Cow<'q, str>>, | ||
| pub fn query_streaming<'c, 'p, 'q, Q>( |
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was lifetime 'p intended for params? It doesn't appear to be needed.
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good catch! removed
| // TODO(sql_server3): Can we maybe re-use this BTreeMap or these Vec | ||
| // allocations? Something to be careful of is shrinking the allocations | ||
| // if/when they grow to large, e.g. from a large spike of changes. | ||
| let mut events: BTreeMap<Lsn, Vec<Operation>> = BTreeMap::default(); |
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Alternatively, could this keep track of a last_lsn and use a vec for accumulating the operations since we know the stream is ordered by lsn? It's much more bookkeeping, not sure it's worth the effort if chunk_size stays small.
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good idea! Added this as a possible todo
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This PR changes the
CdcStream::into_streammethod use a streaming query so we no longer buffer an entire change set into memory and instead everything should be streamed in constant memory, with back pressure, from the network and to our caller.It also removes
mark_completefield onCdcEvent::Data, after chatting with Petros we'll handle cleaning up data in a slightly different way.Motivation
Fixes a
TODO(sql_server1)Checklist
$T ⇔ Proto$Tmapping (possibly in a backwards-incompatible way), then it is tagged with aT-protolabel.