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Update version_downloads.counted last to minimize lock contention #2154

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Merged
bors merged 1 commit into from
Jan 29, 2020
Merged

Update version_downloads.counted last to minimize lock contention #2154

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15 changes: 8 additions & 7 deletions src/tasks/update_downloads.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,11 +52,6 @@ fn collect(conn: &PgConnection, rows: &[VersionDownload]) -> QueryResult<()> {
let amt = download.downloads - download.counted;

conn.transaction::<_, diesel::result::Error, _>(|| {
// increment the number of counted downloads
update(version_downloads::table.find(download.id()))
.set(version_downloads::counted.eq(version_downloads::counted + amt))
.execute(conn)?;

// Update the total number of version downloads
let crate_id = update(versions::table.find(download.version_id))
.set(versions::downloads.eq(versions::downloads + amt))
Expand All @@ -68,12 +63,18 @@ fn collect(conn: &PgConnection, rows: &[VersionDownload]) -> QueryResult<()> {
.set(crates::downloads.eq(crates::downloads + amt))
.execute(conn)?;

// Now that everything else for this crate is done, update the global counter of total
// downloads
// Update the global counter of total downloads
update(metadata::table)
.set(metadata::total_downloads.eq(metadata::total_downloads + i64::from(amt)))
.execute(conn)?;

// Record that these downloads have been propagated to the other tables. This is done
// last, immediately before the transaction is committed, to minimize lock contention
// with counting new downloads.
update(version_downloads::table.find(download.id()))
.set(version_downloads::counted.eq(version_downloads::counted + amt))
.execute(conn)?;

Ok(())
})?;
}
Expand Down