Method calculateForeignTableMemUsage

query/aql_processor.go:1245–1286

calculateForeignTableMemUsage returns how much device memory is needed for foreign table

(memStore memstore.MemStore)

// calculateForeignTableMemUsage returns how much device memory is needed for foreign table
func (qc *AQLQueryContext) calculateForeignTableMemUsage(memStore memstore.MemStore) int {
	var memUsage int

	for joinTableID, join := range qc.Query.Joins {
		// join only support dimension table for now
		// and dimension table is not shared
		shard, err := memStore.GetTableShard(join.Table, 0)
		if err != nil {
			qc.Error = utils.StackError(err, "Failed to get shard for table %s, shard: %d", join.Table, 0)
			return 0
		}

		// only need live store for dimension table
		batchIDs, _ := shard.LiveStore.GetBatchIDs()

		// primary key
		memUsage += int(shard.LiveStore.PrimaryKey.AllocatedBytes())

		// VPs
		for _, batchID := range batchIDs {
			batch := shard.LiveStore.GetBatchForRead(batchID)
			if batch == nil {
				continue
			}

			for _, columnID := range qc.TableScanners[joinTableID+1].Columns {
				usage := qc.TableScanners[joinTableID+1].ColumnUsages[columnID]
				if usage&(columnUsedByAllBatches|columnUsedByLiveBatches) != 0 {
					sourceVP := batch.Columns[columnID]
					if sourceVP == nil {
						continue
					}
					memUsage += int(sourceVP.GetBytes())
				}
			}
			batch.RUnlock()
		}
		shard.Users.Done()
	}

	return memUsage
}

// FindDeviceForQuery calls device manager to find a device for the query
func (qc *AQLQueryContext) FindDeviceForQuery(memStore memstore.MemStore, preferredDevice int,