Hi, > Is it practical with MVStore to use a single key with a list as the value containing the row id's for a simple single column index?
Yes, unless the list of values doesn't fit in memory. Well, if the list of values is very big (multiple KB) *and* changes a lot (many writes operations) then you probably shouldn't do that for performance reasons, but it's possible. But you could also use separate keys. If the key is large (many bytes) and the value is small, then you should enable compression unless file size isn't an issue. Regards, Thomas On Thu, Aug 29, 2013 at 4:37 PM, Thomas Mueller < [email protected]> wrote: > Hi, > > > > I have been experimenting with mapDB but having some problems > > As far as I understand, MapDB should support it as well. What kind of > problems did you run into (just curious)? > > > > One requirement of my project requires importing of the large Geonames > database (www.geonames.org) > > Thats very interesting! I guess using compression should help a lot in > this case, and possibly using a larger page size - specially if you have > more reads than writes. > > Regards, > Thomas > > > > On Thu, Aug 29, 2013 at 3:04 PM, Paul F Fraser <[email protected]>wrote: > >> On 29/08/13 22:45, Thomas Mueller wrote: >> >> Hi, >> >> Why do you want to know, do you want to build you own secondary index >> and use MVStore directly? >> >> >> yes. >> >> I have been experimenting with mapDB but having some problems. Tried the >> same approach with MVStore and it worked without problems. One requirement >> of my project requires importing of the large Geonames database ( www.* >> geonames*.org) which ends up as a db file well in excess of 1G. >> I also think the single file will be an advantage in my project. >> >> >> For the MVTableEngine, currently, the key of an index is a "Value", >> actually a "ValueArray". The last value of the ValueArray is the row id >> (which matches the primary key for bigint or int primary keys). See also >> the MVSecondaryIndex class. But this is an implementation detail, and might >> change later. >> >> >> Is it practical with MVStore to use a single key with a list as the value >> containing the row id's for a simple single column index? >> >> >> Regards, >> Thomas >> >> >> >> On Thu, Aug 29, 2013 at 2:34 PM, Paul F Fraser <[email protected]>wrote: >> >>> The available info on non-unique keys in MVStore states that the plan is >>> to use map key as index columns (combined). One of the index columns is >>> always the row Id. >>> >>> When the key is put to the map, is the key kept as an array or are the >>> entries in the array concatenated somehow? >>> >>> How is the set of keys matching the desired index value retrieved? >>> >>> regards >>> >>> Paul Fraser >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "H2 Database" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at http://groups.google.com/group/h2-database. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "H2 Database" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/h2-database. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "H2 Database" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/h2-database. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- You received this message because you are subscribed to the Google Groups "H2 Database" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/h2-database. For more options, visit https://groups.google.com/groups/opt_out.
