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Jaime- Porque no utiliza Bitmap? *Saludos Cordiales desde EEUU* Martin ______________________________________________ Disclaimer and confidentiality note Everything in this e-mail and any attachments relates to the official business of Sender. This transmission is of a confidential nature and Sender does not endorse distribution to any party other than intended recipient. Sender does not necessarily endorse content contained within this transmission. > Date: Mon, 12 Jan 2009 16:20:40 -0500 > From: jcasanov@xxxxxxxxxxxxxxxxxxx > To: regmeplease@xxxxxxxxx > Subject: Re: Indexing columns with low cardinality: persistent bitmap indexes? > CC: pgsql-general@xxxxxxxxxxxxxx; bruno.lavoie@xxxxxxxxx > > On Mon, Jan 12, 2009 at 4:16 PM, Reg Me Please <regmeplease@xxxxxxxxx> wrote: > > On Monday 12 January 2009 21:38:02 Bruno Lavoie wrote: > >> Hello, > >> > >> I have a column with a small number of distinct values, indexing this > >> one with a standard BTree is useless. How do I can index this column > >> efficiently? I searched and it seems that pg doesn't support the > >> creation of persistent bitmap indexes... Is that feature planned in next > >> releases of pg? > >> > >> Thanks > >> Bruno Lavoie > > > > I would try partial indexes, as many as the distinct values. > > I'm not sure this would help, though. > > > > you should create partial indexes only on those values that are a > lower fraction on the table > ie: if you have > > value "fraction of the table that has this value" > 1 5% > 2 3% > 3 20% > 4 25% > 5 47% > > then only partial indexes on values 1 and 2 are of some value > > -- > Atentamente, > Jaime Casanova > Soporte y capacitación de PostgreSQL > Asesoría y desarrollo de sistemas > Guayaquil - Ecuador > Cel. +59387171157 > > -- > Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general Windows Live™: Keep your life in sync. Check it out. |
