[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Attachment: hive.223.4.patch when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.3.txt, 223.patch1.txt, hive.223.4.patch, patch.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Attachment: patch.txt when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.3.txt, 223.patch1.txt, patch.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Status: Patch Available (was: Open) fixed a small bug when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Status: Patch Available (was: Open) when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.3.txt, 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Status: Open (was: Patch Available) when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.3.txt, 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Attachment: 223.3.txt when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.3.txt, 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Status: Patch Available (was: Open) fixed the bug that joy spotted, and also performed some code cleanup when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Attachment: 223.2.txt when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.2.txt, 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Attachment: 223.patch1.txt when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Updated: (HIVE-223) when using map-side aggregates - perform single map-reduce group-by
[ https://issues.apache.org/jira/browse/HIVE-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Namit Jain updated HIVE-223: Status: Patch Available (was: Open) In a follow-up, I will do the following: In case of map-side aggregates, keep a count of hash table entries and the total entries on the map side. If the ratio is bad, assume that the user made a mistake, and switch to non map-side aggregation plan. when using map-side aggregates - perform single map-reduce group-by --- Key: HIVE-223 URL: https://issues.apache.org/jira/browse/HIVE-223 Project: Hadoop Hive Issue Type: Improvement Components: Query Processor Reporter: Joydeep Sen Sarma Assignee: Namit Jain Attachments: 223.patch1.txt today even when we do map side aggregates - we do multiple map-reduce jobs. however - the reason for doing multiple map-reduce group-bys (for single group-bys) was the fear of skews. When we are doing map side aggregates - skews should not exist for the most part. There can be two reason for skews: - large number of entries for a single grouping set - map side aggregates should take care of this - badness in hash function that sends too much stuff to one reducer - we should be able to take care of this by having good hash functions (and prime number reducer counts) So i think we should be able to do a single stage map-reduce when doing map-side aggregates. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
