Skip to content

Avoid snapshot in ALTER SINK if the sink has made progress #34588

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
martykulma merged 3 commits into from
Dec 23, 2025
Merged

Avoid snapshot in ALTER SINK if the sink has made progress #34588

Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
154b7ab
Avoid snapshot in ALTER SINK if the sink has made progress
martykulma Dec 19, 2025
564bd38
improve comment
martykulma Dec 23, 2025
250d19f
move snapshot determination to storage-controller
martykulma Dec 23, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 6 additions & 1 deletion src/adapter/src/coord/sequencer/inner.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,7 @@ use mz_storage_types::connections::inline::IntoInlineConnection;
use mz_storage_types::controller::StorageError;
use mz_transform::dataflow::DataflowMetainfo;
use smallvec::SmallVec;
use timely::PartialOrder;
use timely::progress::Antichain;
use tokio::sync::{oneshot, watch};
use tracing::{Instrument, Span, info, warn};
Expand Down Expand Up @@ -3406,6 +3407,10 @@ impl Coordinator {
&**write_frontier
);

// For `ALTER SINK`, the snapshot should only occur if the sink has not made any progress.
// This prevents unnecessary decoding in the sink.
let alter_sink_snapshot = with_snapshot && !PartialOrder::less_than(&as_of, write_frontier);
Copy link
Contributor

@patrickwwbutler patrickwwbutler Dec 23, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

newbie question: would LEQ instead of strict less_than not be right here? Is it possible for the as_of and write_frontier to be exactly equal? In that case is it possible that there is actually progress being made?

Copy link
Contributor Author

@martykulma martykulma Dec 23, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The as_of is where we are reading from, and the upper is where the next write will happen. If the write frontier hasn't progressed strictly beyond the as_of, it would mean that nothing has been written (or we are not done writing).

For a simple example, consider the case where as_of is the minimum, e.g. [0], and the upper is also the minimum [0]. In this case, I need to write the snapshot, which happens at [0], and the upper can progress (lets say it is now [1]). At this point, we know that all data associated with times less than, but not equal to, [1] are written.


// Parse the `create_sql` so we can update it to the new sink definition.
//
// Note that we need to use the `create_sql` from the catalog here, not the one from the
Expand Down Expand Up @@ -3484,7 +3489,7 @@ impl Coordinator {
.into_inline_connection(self.catalog().state()),
envelope: sink_plan.envelope,
as_of,
with_snapshot,
with_snapshot: alter_sink_snapshot,
version: sink_plan.version,
from_storage_metadata: (),
to_storage_metadata: (),
Expand Down