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Fix performance issue with many duplicate ids #40

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merged 1 commit into from
Oct 15, 2024
Merged

Fix performance issue with many duplicate ids #40

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10 changes: 3 additions & 7 deletions crates/core/src/sync_local.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,21 +55,17 @@ pub fn sync_local(db: *mut sqlite::sqlite3, _data: &str) -> Result<i64, SQLiteEr

// Query for updated objects

// QUERY PLAN
// |--SCAN buckets
// |--SEARCH b USING INDEX ps_oplog_by_opid (bucket=? AND op_id>?)
// |--SEARCH r USING INDEX ps_oplog_by_row (row_type=? AND row_id=?)
// `--USE TEMP B-TREE FOR GROUP BY
// language=SQLite
let statement = db
.prepare_v2(
"\
-- 1. Filter oplog by the ops added but not applied yet (oplog b).
-- SELECT DISTINCT / UNION is important for cases with many duplicate ids.
WITH updated_rows AS (
SELECT b.row_type, b.row_id FROM ps_buckets AS buckets
SELECT DISTINCT b.row_type, b.row_id FROM ps_buckets AS buckets
CROSS JOIN ps_oplog AS b ON b.bucket = buckets.id
AND (b.op_id > buckets.last_applied_op)
UNION ALL SELECT row_type, row_id FROM ps_updated_rows
UNION SELECT row_type, row_id FROM ps_updated_rows
)

-- 3. Group the objects from different buckets together into a single one (ops).
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