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**WIP** feat(cass): add shardKey to partKey table #1361

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@alextheimer alextheimer commented Apr 6, 2022

Adds a Cassandra table that maps shard keys to partition keys.

    s"""CREATE TABLE IF NOT EXISTS $tableString (
       |    shardKey blob,
       |    partKey blob,
       |    PRIMARY KEY (shardKey, partKey)
       |    ...

Now, all time-series partition keys for a given shard key can be efficiently scanned.

@alextheimer alextheimer force-pushed the ns-mig branch 2 times, most recently from 5aa7797 to 69ab230 Compare April 8, 2022 06:59
Comment on lines +551 to +562
def records(ds: Dataset, readerSeq: Seq[RowReader]): SomeData = {
val builder = new RecordBuilder(MemFactory.onHeapFactory)
readerSeq.foreach { row => builder.addFromReader(row, ds.schema) }
builder.allContainers.zipWithIndex.map { case (container, i) => SomeData(container, i) }.head
}

def partKeyFromRecords(ds: Dataset, records: SomeData, builder: Option[RecordBuilder] = None): Seq[Long] = {
val partKeyBuilder = builder.getOrElse(new RecordBuilder(TestData.nativeMem))
records.records.map { case (base, offset) =>
ds.comparator.buildPartKeyFromIngest(base, offset, partKeyBuilder)
}.toVector
}
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(Almost) mirror the same methods in GdeltTestData.

Comment on lines 86 to +91
val partKeyTablesInit = Observable.fromIterable(0.until(numShards)).map { s =>
getOrCreatePartitionKeysTable(dataset, s)
}.mapEval(t => Task.fromFuture(t.initialize())).toListL
val shardKeyToPartKeyTableInit = Observable.fromIterable(0.until(numShards)).map { s =>
getOrCreateShardKeyToPartKeyTable(dataset, s)
}.mapEval(t => Task.fromFuture(t.initialize())).toListL
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Every PartKeyTable init/insert/delete has a counterpart ShardKeyToPartKeyTable call.

Comment on lines +576 to +577
val shardKeyToPartKeyTableCache = concurrentCache[DatasetRef,
ConcurrentLinkedHashMap[Int, ShardKeyToPartKeyTable]](tableCacheSize)
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Should there be a table per shard (like PartitionKeysTable)?

def scanPartKeysByShardKey(ref: DatasetRef, shard: Int, shardKey: Array[Byte]): Observable[Array[Byte]] = {
val table = getOrCreateShardKeyToPartKeyTable(ref, shard)
table.scanPartKeys(shardKey)
// TODO(a_theimer): figure out if token ranges apply here
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These will only apply if we add extra values to the PK to prevent hot-spotting, right?


val suffix = s"shardKeyToPartKey_$shard"

// TODO(a_theimer): compression settings okay?
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Left the same as PartitionKeyTable

Comment on lines +22 to +23
// TODO(a_theimer): probably need to prevent hot-spotting on a single node
// (i.e. add more fields to [Cassandra's] partition key)
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I won't do this until benchmark tests indicate we need it (or one of you already knows we'll need it).

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