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Showing entries 1 to 11

Displaying posts with tag: db (reset)

My experience with node and mongodb course "M101JS: MongoDB for Node.js Developers" (Third Week)
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Well, currently I am into the third week of mongodb node course "M101JS: MongoDB for Node.js Developers" and I am pretty enjoying it.

Lots of personal learning into node and mongodb.

The third week subject of "Patterns, Case Studies & Tradeoffs" is really interesting.

Here is a list of topics, I learned about:
- Mongodb rich documents concept.
- Mongodb schema use cases.
- Mongodb one:one, one:many, many:many use cases.
- How to select schema based on the usage like whether you want max performance
  or it may be a tradeoff.

One important point, I learned during the course is:
"While relational databases usually go for the normalised 3rd form so that data usage is agnostic to application, but mongodb schema arrangement is very closely related to application usage and varies accordingly."
High Availability with MySQL Fabric: Part I
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In our previous post, we introduced the MySQL Fabric utility and said we would dig deeper into it. This post is the first part of our test of MySQL Fabric’s High Availability (HA) functionality.

Today, we’ll review MySQL Fabric’s HA concepts, and then walk you through the setup of a 3-node cluster with one Primary and two Secondaries, doing a few basic tests with it. In a second post, we will spend more time generating failure scenarios and documenting how Fabric handles them. (MySQL Fabric is an extensible framework to manage large farms of MySQL servers, with support for high-availability and sharding.)

Before we begin, we recommend you read 

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Berkeley DB 5 and PHP
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Everybody working on Unix or in the database world stumbles over Oracle Berkeley DB every now and then. DB is an Open Source embedded database used by applications like OpenLDAP or Postfix. Traditionally it followed mostly a key-value access pattern. Now what caught my attention was the fact that the recently released DB 5.0 provides an SQLite-like C API with the promise of providing better concurrency and performance than regular SQLite. Time to give it a shot.

So I grabbed the source distribution, checked the documentation and saw that I shall use the


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New Database Connect Look in NetBeans 6.7
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Hi all,

If you expand a database connection node in the Services window of the IDE, you'll notice a new look. What are all of these nodes under the connection nodes? They're schemas. For the most part, if you're using Java DB, the only schema you'll need to worry about is the app schema. I'd be interested in knowing what developers have used the other schemas for.

When you expand the MySQL conect node, what you get is a list of databases you've created in MySQL. These database are actually schemas you've created in your MySQL database.

There you have it.

Cheers!

--James

Checking transactions in MySQL
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I'd been doing some stress testing of my mysql application today, and I was hitting some weird cases. Several transactions were deadlocking - this was expected - but the number of records that got inserted into my table was more than the number that I expected after subtracting errors.

My test was fairly simple:
  • Fork 15 processes
  • Insert and update 100 records in each process, running each INSERT/UPDATE pair inside one transaction
  • ROLLBACK on error
  • Either the INSERT or the UPDATE was expected to fail due to deadlock, and the whole transaction should have rolled back leaving no record in the table.

    Before I go on, I should mention that I was using InnoDB, which does support transactions.

    What I expected was that the total number of records in the table + the total number of INSERT/UPDATE aborts due to deadlock should be equal





      [Read more...]
    Read Buffer performance hit
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    I had some fun yesterday with some odd performance problems. So I did a run with oprofile and got this:

    561612   25.0417  /lib64/tls/libc-2.3.4.so memset
    429457   19.1491  /usr/lib/debug/lib/modules/2.6.9-34.ELsmp/vmlinux clear_page
    214268    9.5540  /usr/lib/debug/lib/modules/2.6.9-34.ELsmp/vmlinux do_page_fault
    144293    6.4339  /usr/lib/debug/lib/modules/2.6.9-34.ELsmp/vmlinux do_no_page
    94410     4.2097  /usr/lib/debug/lib/modules/2.6.9-34.ELsmp/vmlinux buffered_rmqueue
    64998     2.8982  /lib64/tls/libc-2.3.4.so memcpy
    59565     2.6559  /usr/lib/debug/lib/modules/2.6.9-34.ELsmp/vmlinux __down_read_trylock
    59369     2.6472 

      [Read more...]
    Updates to NDB/Connectors
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    The NDB/Connectors have added support for Ruby, as well as Asynchronous Transaction support for Java, Python and Perl.

    The Ruby support, of course, means that new you can interact with your MySQL Cluster installation using the NDBAPI from all your Ruby code.

    The async stuff is especially cool, because it means you can send transactions to the Cluster and get responses by way of callbacks defined in the connector language. So you can do something like this:

    class testaclass(object):
    
      def __init__(self, recAttr):
        self.recAttr=recAttr
    
      def __call__(self, ret, myTrans):
        print "value = ", self.recAttr.get_value()
    
    #snip
    
    myTrans = myNdb.startTransaction()
    
    myOper = myTrans.getNdbOperation("mytablename")
    myOper.readTuple(ndbapi.NdbOperation.LM_Read)
    
    myOper.equal("ATTR1", 245755 )
    
    myRecAttr=
      [Read more...]
    NdbObject
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    Here’s a very rough pre-release of NdbObject, an ORM mapping for python that maps Objects to NDB directly with no SQL code.

    NdbObject.tar.bz2

    Recursive idea
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    What if we made a storage engine that used MogileFS to store blobs/images?

    NDB/Python 0.1
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    I’m happy to release version 0.1 of the NDB/Python bindings. They are very young and not very well documented yet, but email me if you are interested in them and especially if you are interested in helping out. I’ll get a Trac system up and going (or something) or maybe sourceforge or savannah or google code or you know, whatever.

    python-ndbapi-0.1.tar.bz2

    primary keys
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    Brad Fitzpatrick has a nice discussion over what people should be using for their ‘id’ keys in a distributed environment. and puts a couple of points forward about why it isn’t such a good idea for his application/architecture. which has a ‘few’ central machines handing out ID’s.

    The is a central problem with sequences that i’ve seen in most DB platforms. That and their 32-bit size. (I think mysql is 32-bit, i’m sure the geeks who read this will correct me)

    The actual question has (If I am reading this correctly) is not about UUID’s vs local-sequences, but how do I move a ‘tree’ of records from one cluster to another, and not have a ID-clash. as if each cluster was independant, it wouldnt be a concern. you would have a central USER->cluster

      [Read more...]
    Showing entries 1 to 11

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