Hi,
I hope you don't get asked this question too often, I've had a look for FAQs but couldn't find anything obvious.
I'm trying to load some data into MonetDB (built on a i386 Debian "etch" box from MonetDB-Feb2008-SuperBall.tar.bz2) and I'm getting strange problems. I've got a table with 11 columns (2 int, 5 varchar, 4 date) and about 38 million rows (the text file I want to pull in is 3.3GB).
If I try COPYing the data in, Monet alternately stops making progress (the computer is reading from the disk slowly, so maybe it's just going to take a *long* time to finish) or crashes with the following message:
!SQLException:importTable:failed to import table !ERROR: GDKload: cannot mmap(): name=24/2470, ext=tail.priv !OS: Cannot allocate memory !ERROR: GDKload failed: name=24/2470, ext=tail.priv
If I try splitting the file into smaller pieces (about a gig each), things work and I end up with the data in the database. It would be nice to know why I needed to split the file up first.
Now I've got the data in I tried running a few queries to make sure everything went OK. I'm getting some very strange results when doing aggregations. The following work:
SELECT count(*) FROM source_livestock; +----------+ | count_ | +==========+ | 37898310 | +----------+
SELECT sex_code, count(*) FROM source_livestock GROUP BY sex_code; +----------+---------------+ | sex_code |count_sex_code | +==========+===============+ | M | 17505304 | | F | 20392997 | | null | 9 | +----------+---------------+
This last query came back amazingly quickly, about ten times faster than Postgres. Monet looks like a fairly amazing database if I can routinely expect queries to be this much faster.
SELECT count(*); +--------------+ | single_value | +==============+ | 1 | +--------------+
but the following don't do what I'd expect:
SELECT count(1); MAPI = monetdb@endemic:50001 ACTION= read_line QUERY = select count(1); ERROR = Connection terminated
I'd expect to get a single row with a single value containing the number 1 from this query. And for the following query I'd expect to get the same, just with the result being zero.
SELECT count(null); !syntax error, unexpected sqlNULL in: "select count(null"
This is how I found the bug:
SELECT sex_code, count(1) FROM source_livestock GROUP BY sex_code; !TypeException:user.s3_1[26]:'aggr.count_no_nil' undefined in: _36:bat[:any,:int] := aggr.count_no_nil(_35:bte, _31:bat[:oid,:oid], _32:bat[:oid,:oid]) !SQLException:sql.rsColumn:Cannot access descriptor !WARNING: BATdescriptor: range error 1
I've come to expect COUNT(*) and COUNT(1) as having the same semantics. But I may be missing something.
SELECT sex_code, count(1+1) FROM source_livestock GROUP BY sex_code; !TypeException:user.s4_1[28]:'aggr.count_no_nil' undefined in: _39:bat[:any,:int] := aggr.count_no_nil(_38:bte, _32:bat[:oid,:oid], _33:bat[:oid,:oid]) +----------+---------------------+ | sex_code |sql_add_single_value | +==========+=====================+ | M | monetdb | +----------+---------------------+
This second one is particularly bad because I get an incorrect answer back. Any idea what I'm doing wrong?
Thanks, Sam