COPY INTO robust to empty row at end of CSV

László Sándor sandorl at gmail.com
Mon May 19 18:06:16 CEST 2014


Stefan,
On the second half of your first email: Why would you prefer me having a
view instead of a new big table (and deleting the annual ones afterwards)?
There is little advantage of them being stored (?) partitioned by year, no?
Doesn't that kill the purpose of the columnar storage anyway? (Though it is
true, for a long panel dataset, most use cases are specific to some years
only, so quick selection based on partitions might speed things up.)

And on the code itself: You would still recommend coding these calls up in
Python, this is much harder (impossible) to code using SQL variables?

Thanks,

Laszlo


On Mon, May 19, 2014 at 8:11 AM, Stefan Manegold <Stefan.Manegold at cwi.nl>wrote:

>
>
> ----- Original Message -----
> > Hi all,
> >
> > Hannes Mühleisen (cc'd) generously shared his
> > homepages.cwi.nl/~hannes/importer.py Python script with me last week,
> which
> > automates the creation of tables from text files: Python's csv-reader
> helps
> > recognize the dialect of the text file as well as grab the header for
> column
> > names and identify the types for the columns, and then a single COPY %i
> > OFFSET %i RECORDS INTO %s FROM \'%s\' USING DELIMITERS … is issued to
> > MonetDB (see line 404 of the script).
> >
> > I had some issues with this over the last three days, but now I see the
> > source of the error I get: There is nothing wrong with Hannes's Python
> code
> > but when COPY INTO turns back to the text file, MonetDB still complains
> > about the last row containing an "incomplete record" (it is empty) even
> if
> > Python was smart enough not to count that row into the number of records
> > beforehand.
> >
> > Is there a way to call COPY INTO that is robust to the text file ending
> in an
> > extra empty row? It is common with some generated CSV or TSV files.
>
> Use COPY n RECORDS ..., where n is the number of non-empty lines in you
> CSV file.
>
> > By the way, I also have a follow-up about how to merge some of the tables
> > together. I am happy to work on this, of course, I don't expect anyone to
> > script this for me, but I am confused about how much I can use SQL
> variables
> > for this (and how) versus how much I need to use another language to
> script
> > the repeated calls to MonetDB about each year for each series of tables
> (I
> > have dozens of dozens). I hope this is a reasonably well-posed question:
> >
> http://dba.stackexchange.com/questions/65329/dynamic-sql-merge-partitioned-tables-annual-tables-into-a-single-table-of-all
>
> Not sure whether the WHILE loops works as such, but you could easily do
> that in your application.
>
> You also might want to consider replacing
>     ALTER TABLE data_ at i ADD COLUMN "year" INTEGER; UPDATE data_ at i SET
> "year" = @i;
> by, say,
>     ALTER TABLE data_ at i ADD COLUMN "year" INTEGER DEFAULT @i;
> and
> CREATE TABLE data AS SELECT * FROM data_1990 UNION ALL SELECT * FROM
> data_1991 UNION ALL [...] WITH DATA;
> by, say,
> CREATE VIEW data AS SELECT * FROM data_1990 UNION ALL SELECT * FROM
> data_1991 UNION ALL [...];
>
> Best,
> Stefan
>
> > Thanks for any help,
> >
> > Laszlo
> >
> > _______________________________________________
> > users-list mailing list
> > users-list at monetdb.org
> > https://www.monetdb.org/mailman/listinfo/users-list
> >
>
> --
> | Stefan.Manegold at CWI.nl | DB Architectures   (DA) |
> | www.CWI.nl/~manegold/  | Science Park 123 (L321) |
> | +31 (0)20 592-4212     | 1098 XG Amsterdam  (NL) |
>
> _______________________________________________
> users-list mailing list
> users-list at monetdb.org
> https://www.monetdb.org/mailman/listinfo/users-list
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.monetdb.org/pipermail/users-list/attachments/20140519/1ce9a0b6/attachment.html>


More information about the users-list mailing list