Hi, I think i have a initial Implementation. It has some bugs and i am working on fixing it. But to show the advantages, I want to show the number of Logical I/Os on the screen. In order to show that, i tried enabling the log_statement option in PostgreSQL.conf. But it shows only the physical reads. What i wanted was a Logical reads count( No. of ReadBuffer calls, which is stored in ReadBufferCount variable). So i have added this stats to the bufmgr.c(function is BufferUsage, i suppose) to show Logical Reads and Physical Reads. Is this a acceptable change? I thought logical read count would be helpful, even for SQL tuning. Since if someone wants to tune the SQL on a test system, things might get cached and he wouldn't know how much I/O his SQL is potentially capable of. May be we can add a statistic to show how many of those ReadBuffers are pinned Buffers.
Expecting your comments. Thanks, Gokul. On 10/14/07, Gokulakannan Somasundaram <[EMAIL PROTECTED]> wrote: > > > > On 10/14/07, Trevor Talbot <[EMAIL PROTECTED]> wrote: > > > > On 10/14/07, Gokulakannan Somasundaram <[EMAIL PROTECTED]> wrote: > > > > > http://www.databasecolumn.com/2007/09/one-size-fits-all.html > > > > > > > The Vertica database(Monet is a open source version with the same > > > > > principle) makes use of the very same principle. Use more disk > > space, > > > > > since they are less costly and optimize the data warehousing. > > > > > What i meant there was, it has duplicated storage of certain columns > > of the > > > table. A table with more than one projection always needs more space, > > than a > > > table with just one projection. By doing this they are reducing the > > number > > > of disk operations. If they are duplicating columns of data to avoid > > reading > > > un-necessary information, we are duplicating the snapshot information > > to > > > avoid going to the table. > > > > Was this about Vertica or MonetDB? I saw that article a while ago, > > and I didn't see anything that suggested Vertica duplicated data, just > > that it organized it differently on disk. What are you seeing as > > being duplicated? > > > Hi Trevor, > This is a good paper to read about the basics of > Column-oriented databases. > http://db.lcs.mit.edu/projects/cstore/vldb.pdf > If you goto the Section 2 - Data Model. He has shown the data model, with > a sample EMP table. > > The example shows that EMP table contains four columns - Name, Age, Dept, > Salary > From this table, projections are being formed - (In the paper, they have > shown the creation of four projections for Example 1) > EMP1 (name, age) > EMP2 (dept, age, DEPT.floor) > EMP3 (name, salary) > DEPT1(dname, floor) > > As you can see, the same column information gets duplicated in different > projections. > The advantage is that if a query is around name and age, it need not skim > around other details. But the storage requirements go high, since there is > redundancy. As you may know, if you increase data redundancy, it will help > selects at the cost of inserts, updates and deletes. > > This is what i was trying to say. > > Thanks, > Gokul. > > >
