+1. This is one of the common use cases in batch scenarios and it will be great to have this in a stream as well using managed state, spillableMultiMap structure.
Regards, Mohit On Thu, May 12, 2016 at 2:38 PM, Yogi Devendra <[email protected] > wrote: > +1 for the Proposal. > > This will be useful for joins involving large amount of data to be held > intermediately. > > ~ Yogi > > On 9 May 2016 at 14:05, Chaitanya Chebolu <[email protected]> > wrote: > > > Hi , > > > > Malhar library has in-memory join operator and this can't process > large > > amount of data because of checkpoint and Memory bottlenecks. To avoid > > these, I am proposing inner join operator using Managed State that is > > recently added to Malhar. > > > > Details of Inner Join operator, Managed State and Design for Inner Join > > operator using Managed State are given below: > > > > Inner Join Operator > > -------------------------- > > Join Operator pairs tuples from two relational streams that matches the > > join condition and emits the paired tuples. > > > > For example, let's say S1 and S2 are two input streams and join condition > > is > > (S1.a.key = S2.b.key) and |S1.a.time - S2.b.time| < t1 > > where a and b are tuples coming on S1 and S2 respectively, t1 is the time > > period > > > > Based on the above join condition, join operator needs to store tuples > for > > "t1" time. Let's say JS1 and JS2 are their respective stores where these > > tuples are stored. > > > > Let (k1, v1) be the tuple coming on Stream S1. Following are the steps > to > > be done for join operation: > > > > 1. Insert (k1, v1) into the store JS1. > > 2. For Key k1, get the values from store JS2. > > 3. If step 2 returns non-null set, apply join conditions > > > > The similar procedure is applied if the tuple is on Stream S2, swapping > JS1 > > and JS2 in the steps above. > > > > Managed State > > -------------------- > > Managed State is an incremental check-pointing and fault-tolerant key > value > > data structure. For more info about Managed State, please have a look at > > the below link: > > > > > > > https://github.com/apache/incubator-apex-malhar/tree/master/library/src/main/java/org/apache/apex/malhar/lib/state/managed > > > > Abstract Join Operator > > -------------------------------- > > Abstract implementation of Join operator is available at > > com.datatorrent.lib.join package. JoinStore is a store interface used in > > join operator and available at the same package. > > For more details about the join operator, please have a look at the > below > > link: > > > > > https://github.com/apache/incubator-apex-malhar/tree/master/library/src/main/java/com/datatorrent/lib/join > > > > Design of Join Operator Using Managed State > > ------------------------------------------------------------- > > We need to provide a concrete store using Managed State and would be like > > as below: > > > > public class ManagedJoinStore extends ManagedTimeStateImpl implements > > JoinStore > > { > > } > > > > Data in Managed store would be in the form of Map of byte[] to byte[]. > > > > If the value is list, then inserting (k1, v1) into the store would be the > > following steps: > > (1) For the key k1, get the value from store JS2. (Here we need to search > > it in all the time buckets, if the key is not present in Memory) > > (2) Convert the above value to List. > > (3) Add the value v1 to the above list. > > (4) Convert the new list to slice. > > (5) Insert (k1, new slice) into the Managed state. > > > > Values as list has been discussed here: > > https://issues.apache.org/jira/browse/APEXMALHAR-2026 > > > > Based on above JIRA, I am suggesting SpillableMultiMap data structure for > > list of values. Let the store would be SpillableMultiMapJoinStore. > > > > Based on above details, store is categorized based on key type. > > > > Key Store > > > -------------------------------------------------------------------------- > > Primary ManagedJoinStore > > Not Primary SpillableMultiMapJoinStore > > > > Following additional properties would be exposed by the Join operator: > > > > - isPrimaryKey - whether the key is primary or not. > > - noOfBuckets - Number of key buckets. This parameter is required for > > Managed State. > > > > Please provide your suggestions. > > > > Regards, > > Chaitanya > > >
