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Displaying posts with tag: aggregation (reset)

Parallel Query for MySQL with Shard-Query
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While Shard-Query can work over multiple nodes, this blog post focuses on using Shard-Query with a single node.  Shard-Query can add parallelism to queries which use partitioned tables.  Very large tables can often be partitioned fairly easily. Shard-Query can leverage partitioning to add paralellism, because each partition can be queried independently. Because MySQL 5.6 supports the partition hint, Shard-Query can add parallelism to any partitioning method (even subpartioning) on 5.6 but it is limited to RANGE/LIST partitioning methods on early versions.

The output from Shard-Query is from the commandline …

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Fun with Bugs #28 - regression bugs in MySQL 5.6
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2013 was a great year for MySQL Community. New MySQL 5.6 GA release with its increased throughput, scalability and new features as well as more interaction and cooperation with MySQL Community from Oracle side brought us a lot of new perspectives and good feelings over the year.

Unfortunately new MySQL 5.6 GA release also reminded about old and well known problem with new MySQL versions. They all introduce new regression bugs. MySQL 5.6 had not become an exception.

Note that according to good old tradition (that I hope will be …



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Advantages of weighted lists in RDBMS processing
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A list is simply a list of things. The list has no structure, except in some cases, the length of the list may be known. The list may contain duplicate items. In the following example the number 1 is included twice.

Example list:

1
2
3
1


A set is similar to a list, but has the following differences:

  1. The size of the set is always known
  2. A set may not contain duplicates

You can convert a list to a set by creating a 'weighted list'. The weighted list includes a count column so that you can determine when an item in the …







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I wrote a new tool that runs aggregation queries over MySQL sharded databases using Gearman.
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I created a new tool this week:
http://code.google.com/p/shard-query

As the name Shard-Query suggests, the goal of the tool is to run a query over multiple shards, and to return the combined results together as a unified query. It uses Gearman to ask each server for a set of rows and then runs the query over the combined set. This isn't a new idea, however, Shard-Query is different than other Gearman examples I've seen, because it supports aggregation.

It does this by doing some basic query rewriting based on the input query.

Take this query for example:









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Showing entries 1 to 4

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