This document discusses the future of HCatalog, which provides a table abstraction and metadata layer for Hadoop data. It summarizes Alan Gates' background with Hadoop projects like Pig and Hive. It then outlines how HCatalog opens up metadata to MapReduce and Pig. It describes the Templeton REST API for HCatalog and how it allows creating, describing and listing tables. It proposes using HCatReader and HCatWriter to read and write data between Hadoop and parallel systems in a language-independent way. It also discusses using HCatalog to store semi-structured data and improving ODBC/JDBC access to Hive through a REST server.

1. Future of HCatalog
Alan F. Gates
@alanfgates
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2. Who Am I?
• HCatalog committer and mentor
• Co-founder of Hortonworks
• Lead for Pig, Hive, and HCatalog at Hortonworks
• Pig committer and PMC Member
• Member of Apache Software Foundation and Incubator
PMC
• Author of Programming Pig from O’Reilly
© Hortonworks Inc. 2012
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3. Hadoop Ecosystem
MapReduce Hive Pig
SerDe
InputFormat/ InputFormat/ Load/
Metastore Client
OuputFormat OuputFormat Store
HDFS
Metastore
© Hortonworks 2012
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4. Opening up Metadata to MR & Pig
MapReduce Hive Pig
HCaInputFormat/ HCatLoader/
HCatOuputFormat HCatStorer
SerDe
InputFormat/
Metastore Client
OuputFormat
HDFS
Metastore
© Hortonworks 2012
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5. Templeton - REST API
• REST endpoints: databases, tables, partitions, columns, table properties
• PUT to create/update, GET to list or describe, DELETE to drop
Get a list of all tables in the default database:
GET
http://…/v1/ddl/database/default/table
Hadoop/
HCatalog
{
"tables": ["counted","processed",],
"database": "default"
}
© Hortonworks 2012
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6. Templeton - REST API
• REST endpoints: databases, tables, partitions, columns, table properties
• PUT to create/update, GET to list or describe, DELETE to drop
Create new table “rawevents”
PUT
{"columns": [{ "name": "url", "type": "string" },
{ "name": "user", "type": "string"}],
"partitionedBy": [{ "name": "ds", "type": "string" }]}
http://…/v1/ddl/database/default/table/rawevents
Hadoop/
HCatalog
{
"table": "rawevents",
"database": "default”
}
© Hortonworks 2012
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7. Templeton - REST API
• REST endpoints: databases, tables, partitions, columns, table properties
• PUT to create/update, GET to list or describe, DELETE to drop
Describe table “rawevents”
GET
http://…/v1/ddl/database/default/table/rawevents
Hadoop/
HCatalog
{
"columns": [{"name": "url","type": "string"},
{"name": "user","type": "string"}],
"database": "default",
"table": "rawevents"
}
• Included in HDP
• Not yet checked in, but you can find the code on Apache’s JIRA HCATALOG-182
© Hortonworks 2012
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8. Reading and Writing Data in Parallel
• Use Case: Users want
– to read and write records in parallel between Hadoop and their parallel system
– driven by their system
– in a language independent way
– without needing to understand Hadoop’s file formats
• Example: an MPP data store wants to read data out of Hadoop as
HCatRecords for its parallel jobs
• What exists today
– webhdfs
– Language independent
– Can move data in parallel
– Driven from the user side
– Moves only bytes, no understanding of file format
– Sqoop
– Can move data in parallel
– Understands data format
– Driven from Hadoop side
– Requires connector or JDBC
© 2012 Hortonworks
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9. HCatReader and HCatWriter
getHCatReader
Master HCatalog
HCatReader
read
Input Slave
Splits Iterator<HCatRecord>
read
Slave HDFS
Iterator<HCatRecord>
read
Slave
Iterator<HCatRecord>
Right now all in Java, needs to be REST
© 2012 Hortonworks
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10. Storing Semi-/Unstructured Data
Table Users File Users
Name Zip {"name":"alice","zip":"93201"}
Alice 93201 {"name":"bob”,"zip":"76331"}
Bob 76331 {"name":"cindy"}
{"zip":"87890"}
select name, zip A = load ‘Users’ as
from users; (name:chararray, zip:chararray);
B = foreach A generate name, zip;
© Hortonworks Inc. 2012
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11. Storing Semi-/Unstructured Data
Table Users File Users
Name Zip {"name":"alice","zip":"93201"}
Alice 93201 {"name":"bob”,"zip":"76331"}
Bob 76331 {"name":"cindy"}
{"zip":"87890"}
A = load ‘Users’ as
(name:chararray, zip:chararray);
B = foreach A generate name, zip;
select name, zip
from users;
A = load ‘Users’
B = foreach A generate name, zip;
© Hortonworks Inc. 2012
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12. Storing Semi-/Unstructured Data
Table Users File Users
Name Zip {"name":"alice","zip":"93201"}
Alice 93201 {"name":"bob”,"zip":"76331"}
Bob 76331 {"name":"cindy"}
{"zip":"87890"}
A = load ‘Users’ as
(name:chararray,
zip:chararray);
B = foreach A generate name, zip;
select name, zip A = load ‘Users’
from users; B = foreach A generate name, zip;
© Hortonworks Inc. 2012
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13. Hive ODBC/JDBC Today
Issue: Have to have Hive
JDBC code on the client
Client
Hive Hadoop
Server
Issues:
• Not concurrent
ODBC • Not secure
Client • Not scalable
Issue: Open source version
not easy to use
© 2012 Hortonworks
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14. ODBC/JDBC Proposal
JDBC
Client
Provide robust open source REST Hadoop
implementations Server
• Spawns job inside cluster
ODBC • Runs job as submitting user
Client • Works with security
• Scaling web services well understood
© 2012 Hortonworks
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15. Questions
© 2012 Hortonworks
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