Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Hi Rob: On Tue, Aug 23, 2016 at 4:52 PM, Rob Sargent wrote: > By 'this' I was referring to the optimizations mentioned, and am wondering > if this holds true under user load. For that you'll have to refer to the source, or ask someone more versed in pg source arcanes. >

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

On 08/23/2016 08:34 AM, Francisco Olarte wrote: On Tue, Aug 23, 2016 at 4:28 PM, Rob Sargent wrote: On 08/23/2016 07:44 AM, Francisco Olarte wrote: On Tue, Aug 23, 2016 at 2:26 PM, pinker wrote: I am just surprised by the order of magnitude in the

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

On Tue, Aug 23, 2016 at 4:28 PM, Rob Sargent wrote: > On 08/23/2016 07:44 AM, Francisco Olarte wrote: >> On Tue, Aug 23, 2016 at 2:26 PM, pinker wrote: >>> I am just surprised by the order of magnitude in the difference though. 2 >>> and 27 minutes that's

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

On 08/23/2016 07:44 AM, Francisco Olarte wrote: Hi pinker: On Tue, Aug 23, 2016 at 2:26 PM, pinker wrote: I am just surprised by the order of magnitude in the difference though. 2 and 27 minutes that's the huge difference... I did another, simplified test, to make sure there

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Hi pinker: On Tue, Aug 23, 2016 at 2:26 PM, pinker wrote: > I am just surprised by the order of magnitude in the difference though. 2 > and 27 minutes that's the huge difference... I did another, simplified test, > to make sure there is no duplicates and the only difference

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Francisco Olarte wrote > It's already been told that btrees work that way, if you find itstrange > read a bit about them, this is completely normal, but ... I am just surprised by the order of magnitude in the difference though. 2 and 27 minutes that's the huge difference...I did another,

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

On Fri, Aug 19, 2016 at 3:20 PM, Daniel Verite wrote: > There's a simple technique that works on top of a Feistel network, > called the cycle-walking cipher. Described for instance at: > http://web.cs.ucdavis.edu/~rogaway/papers/subset.pdf > I'm using the opportunity to

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Francisco Olarte wrote: > I think there are some pseudo-random number generators which > can be made to work with any range, but do not recall which ones right > now. There's a simple technique that works on top of a Feistel network, called the cycle-walking cipher. Described for

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Daniel: On Thu, Aug 18, 2016 at 5:24 PM, Daniel Verite wrote: >> unless you know of an easy way to generate a random permutation on the >> fly without using a lot of memory, I do not. > It could be done by encrypting the stream. > For 32 bits integers: >

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Francisco Olarte wrote: > unless you know of an easy way to generate a random permutation on the > fly without using a lot of memory, I do not. It could be done by encrypting the stream. For 32 bits integers: https://wiki.postgresql.org/wiki/Skip32 For 64 bits integers:

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Hi: On Thu, Aug 18, 2016 at 1:32 PM, pinker wrote: ... > create table t01 (id bigint); > create index i01 on t01(id); > insert into t01 SELECT s from generate_series(1,1000) as s; > > and random values: > create table t02 (id bigint); > create index i02 on t02(id); > insert

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

W dniu 2016-08-18 14:19:25 użytkownik Ilya Kazakevich napisał: > >Thank you. So if that is the reason changing the fillfactor parameter should > >help? > > Fillfactor is not about rebalancing, but about page split. If you have many > insertions you may decrease

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

>Thank you. So if that is the reason changing the fillfactor parameter should >help? Fillfactor is not about rebalancing, but about page split. If you have many insertions you may decrease fillfactor to minimize page splits, but I am not sure it will help in your case. But you should try)

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

W dniu 2016-08-18 14:00:31 użytkownik Ilya Kazakevich napisał: > Hi, > > >What's the reason that postgres needs more index pages to store random > >data > >than sequential ones? > > I assume that is because B-Tree is self-balanced tree, so it needs to be >

Re: [GENERAL] Sequential vs. random values - number of pages in B-tree

Hi, >What's the reason that postgres needs more index pages to store random >data >than sequential ones? I assume that is because B-Tree is self-balanced tree, so it needs to be rebalanced after each insertion. Random insertions may go to the head of index where no space left leading to huge

[GENERAL] Sequential vs. random values - number of pages in B-tree

Hi! After doing a quick test: with sequential values: create table t01 (id bigint); create index i01 on t01(id); insert into t01 SELECT s from generate_series(1,1000) as s; and random values: create table t02 (id bigint); create index i02 on t02(id); insert into t02 SELECT random()*100 from