HadoopDB: an architectural hybrid of MapReduce and DBMS technologies for analytical workloads (VLDB '09)

912 2012-11-20 16:20

Large analytical data management (OLAP) with commodity clusters

Performance and efficiency
- hadoop
  - is not for structured data analysis
  - scale well
  - open source, without cost
scalability, fault-tolerance, and flexibility
- Previous parallel db fit into tens of nodes, not thousand of nodes.
- not scale well for failures, heterogeneous machines, performance untested

MapReduce (Hadoop) + parallel db (or single-node DBs) = HadoopDB
- Translation layer: Hive
- Communication layer: Hadoop
- Database layer: PostgreSQL (or MySQL, … JDBC)
Components
1. Database Connector
  - Interface among dbs on nodes
  - extends InputFormat class -> InputFormat Implementation lib
  - JDBC-complaint
2. Catalog
  - metainformation as XML = connection para + metadata
3. Data Loader
  - Global Hasher: MR, repartition raw data from HDFS to NO. of nodes
  - Local Hasher: copy from HDFS, repartition the partition into chunks
  - Better load balance than Hadoop
4. SQL - MR - SQL (SMS) Planner
  - extend Hive for
  - open and low cost
  - each table stored separately in HDFS, low performance in multi-table trans. intercept normal Hive flow in
  1. update MetaStore before query execution
  2. between query plan generation and MR jobs retrieve fields, determine partition keys
  traverse DAG bottom-up
  
  only support filter, select, aggregation
Extend performance [23] with fault tolerance and heterogeneous node exp

TODO: modify the current task scheduler, connect not straggler node but the replicas.

Exp on EC2, Hadoop, HadoopDB, Vertica, DBMS-X

HadoopDB’s performance < parallel db for
- PostgreSQL (not column-store, not compression)
- Hadoop and Hive are young

[23] A Comparison of Approaches to Large Scale Data Analysis

[6] Scope [11] Hive [24] C-store [4] What is the right way to measure scale?

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