Re: [Pytables-users] Determining effect of compression

2012-03-28 Thread Francesc Alted
In case you want more feedback on compression filters, this study might be interesting for you: http://gael-varoquaux.info/blog/?p=159 Francesc On 3/28/12 12:33 PM, Alvaro Tejero Cantero wrote: > Hi, > > Trying to evaluate compression filters, I was looking for a call in > PyTables to get the s

Re: [Pytables-users] Determining effect of compression

2012-03-28 Thread Anthony Scopatz
On Wed, Mar 28, 2012 at 1:05 PM, Francesc Alted wrote: > On 3/28/12 12:33 PM, Alvaro Tejero Cantero wrote: > > Hi, > > > > Trying to evaluate compression filters, I was looking for a call in > > PyTables to get the size of a dataset (in bytes). As I didn't find it > > I remembered the many benchm

Re: [Pytables-users] Determining effect of compression

2012-03-28 Thread Francesc Alted
On 3/28/12 12:33 PM, Alvaro Tejero Cantero wrote: > Hi, > > Trying to evaluate compression filters, I was looking for a call in > PyTables to get the size of a dataset (in bytes). As I didn't find it > I remembered the many benchmarks and found instead [1] that the way to > do it is to create singl

Re: [Pytables-users] Table.where and conditions across tables

2012-03-28 Thread Francesc Alted
On 3/28/12 10:15 AM, Alvaro Tejero Cantero wrote: > That is a perfectly fine solution for me, as long as the arrays aren't > copied in memory for the query. No, the arrays are not copied in memory. They are just read from disk block-by-block and then the output is directed to the iterator, or an

[Pytables-users] Determining effect of compression

2012-03-28 Thread Alvaro Tejero Cantero
Hi, Trying to evaluate compression filters, I was looking for a call in PyTables to get the size of a dataset (in bytes). As I didn't find it I remembered the many benchmarks and found instead [1] that the way to do it is to create single-dataset files and interrogate the filesystem. Curiously eno

Re: [Pytables-users] Table.where and conditions across tables

2012-03-28 Thread Alvaro Tejero Cantero
That is a perfectly fine solution for me, as long as the arrays aren't copied in memory for the query. Thank you! Thinking that your proposed solution uses iterables to avoid it I tried boolcond = pt.Expr('(exp(a)<0.9)&(a*b>0.7)|(b*sin(a)<0.1)') indices = [i for i,v in boolcond if v] (...) TypeE

Re: [Pytables-users] Table.where and conditions across tables

2012-03-28 Thread Francesc Alted
On 3/27/12 6:34 PM, Francesc Alted wrote: > Another option that occurred to me recently is to save all your > columns as unidimensional arrays (Array object, or, if you want > compression, a CArray or EArray), and then use them as components of a > boolean expression using the class `tables.Expr