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mongo: partition snapshots for numeric and string _id collections #4487

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Merged
jgao54 merged 6 commits into from
Jul 2, 2026
Merged

mongo: partition snapshots for numeric and string _id collections #4487

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f45c14e
mongo: partition snapshots for numeric and string _id collections
andreyzhelnin-st Jun 23, 2026
925889b
mongo: address PR review comments on _id partitioning
andreyzhelnin-st Jun 25, 2026
8dac193
mongo: reduce e2e test doc count to 100 for faster local runs
andreyzhelnin-st Jun 25, 2026
b89e2fc
mongo: address PR review comments (round 2)
andreyzhelnin-st Jun 26, 2026
c21475e
fix(lint): restore stdlib import group separator in qrep_partition.go
andreyzhelnin-st Jun 26, 2026
1a11c54
Merge remote-tracking branch 'origin/main' into mongo-id-partitioning
ilidemi Jul 2, 2026
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37 changes: 26 additions & 11 deletions flow/connectors/mongo/qrep.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,17 +26,9 @@ func (c *MongoConnector) GetQRepPartitions(
config *protos.QRepConfig,
last *protos.QRepPartition,
) ([]*protos.QRepPartition, error) {
fullTablePartition := []*protos.QRepPartition{
{
PartitionId: utils.FullTablePartitionID,
Range: nil,
FullTablePartition: true,
},
}

if config.WatermarkColumn != DefaultDocumentKeyColumnName {
c.logger.Warn("unexpected watermark column, falling back to full table partition")
return fullTablePartition, nil
return utils.FullTablePartition(), nil
}

if config.NumRowsPerPartition <= 0 {
Expand Down Expand Up @@ -70,10 +62,10 @@ func (c *MongoConnector) GetQRepPartitions(

if adjustedPartitions.AdjustedNumPartitions <= 1 {
c.logger.Info("[mongo] insufficient partitions for parallel snapshot, falling back to full table partition")
return fullTablePartition, nil
return utils.FullTablePartition(), nil
}

return c.minMaxPartitions(ctx, collection, adjustedPartitions.AdjustedNumPartitions)
return c.buildPartitions(ctx, collection, adjustedPartitions.AdjustedNumPartitions)
}

func (c *MongoConnector) GetDefaultPartitionKeyForTables(
Expand Down Expand Up @@ -234,6 +226,29 @@ func toRangeFilter(watermarkColumn string, partitionRange *protos.PartitionRange
bson.E{Key: "$lte", Value: endObjectID},
}},
}, nil
case *protos.PartitionRange_IntRange:
// Numeric _id: inclusive range. PartitionHelper builds non-overlapping
// [start, end] integer ranges. Mongo compares int32/int64 numerically, so
// int64 bounds match int32-typed _ids.
return bson.D{
bson.E{Key: watermarkColumn, Value: bson.D{
bson.E{Key: "$gte", Value: r.IntRange.Start},
bson.E{Key: "$lte", Value: r.IntRange.End},
}},
}, nil
Comment on lines +229 to +238

@jgao54 jgao54 Jun 25, 2026 •
edited
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for mongo, using inclusive-inclusive int range [start, end] is prone to missing data in the rare scenario where user has doubles mixed in with integers. For example, if the _ids are 1, 2, 2.5, 3, 4; min/max will show up as 1 and 4, ended up with ranges [1, 2], [3, 4], we'd miss the 2.5 document.

we could introduce a NumericPartitionRange and use inclusive-exclusive [start, end), similar to StringPartitionRange, to avoid any gaps.

(While Mongo sorts by type so we don't have to worry about this for ObjectIDs, all numeric types are in the same type bucket)

case *protos.PartitionRange_StringRange:
// String _id: half-open [start, end) for all but the last partition;
// the last partition is closed [start, end] (EndInclusive == true).
endOp := "$lt"
if r.StringRange.EndInclusive {
endOp = "$lte"
}
return bson.D{
bson.E{Key: watermarkColumn, Value: bson.D{
bson.E{Key: "$gte", Value: r.StringRange.Start},
bson.E{Key: endOp, Value: r.StringRange.End},
}},
}, nil
default:
return nil, fmt.Errorf("unsupported partition range type")
}
Expand Down
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