- users-list - monetdb.org

[MonetDB-users] Prepare statements as performance upgrade?
by Stefan de Konink 12 Jan '12

12 Jan '12

Hi, When I look into the executemany implementation of the Python DBAPI, I see that executemany is implemented as loop over the parameters given the same statement. In the mapi documentation there is written about using mapi_prepare_array() and mapi_execute_array(). Would such thing be beneficial in the general case? In my own program I have the following: while True: received = data_from_network() update_monetdb(received) It seems that the standard DBAPI doesn't expose prepared statements as some sort of transparent usage, so using SQL PREPARE sounds as the most logical way. What is the SQL statement to 'forget' the stored prepared statement? Stefan

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[MonetDB-users] Disk space of a table
by Vassilis Papakonstantinou 11 Jan '12

11 Jan '12

Hello, Is there a way to get the disk space of a table? Vassilis

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[MonetDB-users] how to load NaN as REAL
by bigu 10 Jan '12

10 Jan '12

I have a csv file and some columns are defined as REAL. The values some time have 'NaN' so when trying to load in the db it says cannot load NaN into REAL. COPY 1000000 OFFSET 2 RECORDS into mytable from 'C:\temp.csv' delimiters ',', '\n'; SQLException:importTable:value 'NaN' from line 11 field 10 not inserted, expecting type real failed to import table -- View this message in context: http://old.nabble.com/how-to-load-NaN-as-REAL-tp33107777p33107777.html Sent from the monetdb-users mailing list archive at Nabble.com.

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[MonetDB-users] load CSV without header row
by bigu 09 Jan '12

09 Jan '12

Today installed monetdb for first time and wanted to play with some of the features but stuck with loading the file. Excuse me if this looks too basic. There is a 3GB csv file (1M rows and 400 columns). I am trying load in monetdb on my windows 7 machine. I first created a table mostly data is numeric exect for few that are metadata strings. How do i load this file without removing the header. The error says column_name not of type integer since the column_name is the actual header string but the values are integers. I can remove the header manually before loading but if i plan to scale then it is not a good option. Is there a way to say load "n" records from file starting at 'x' to 'y'? or ignore first line. COPY 1000000 RECORDS into mytable from 'C:\data.csv' delimiters ',', '\n'; Thanks. -- View this message in context: http://old.nabble.com/load-CSV-without-header-row-tp33096188p33096188.html Sent from the monetdb-users mailing list archive at Nabble.com.

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[MonetDB-users] [PATCH]: python-monetdb does not support RIPEMD160
by W-Mark Kubacki 09 Jan '12

09 Jan '12

Hello! Although MonetDB supports RIPEMD160, python-monetdb (version 11.5.9) does not. Patch [1] fixes that. Unfortunately Python's hashlib.algorithms and dir(hashlib) is "incomplete" in this regards and lists only algorithms which are guaranteed to be supported. Yet more are actually implemented. The patch moves the responsibility for checking whether RIPEMD160 (and others) is supported to hashlib, retaining the NotSupportedError. -- Mark Kubacki [1] https://raw.github.com/wmark/ossdl-overlay/master/dev-python/python-monetdb…

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[MonetDB-users] Max Connection Limit
by Joseph Brower 06 Jan '12

06 Jan '12

Right now we are hitting the limit of 64 connections to MonetDB. We're working on some middleware that will consolidate those into only 2 or 3 connections, but until we finish it, we need to increase the limit. How do we go about doing that? Thanks, Joseph Brower

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[MonetDB-users] Error in SELECT from a function via Mapi
by Iain Buchanan 02 Jan '12

02 Jan '12

Hi, I'm having problems calling a function via the Mapi interface (using Visual C++ under Windows and the 15th November download). It works fine when I call it directly, but fails when I call via Mapi. I create the function: create function tick.dummy(a integer) returns table (entry integer) begin return (select 1); end; I can then call this directly from mclient without any problems: sql>select entry from tick.dummy(1); +-------+ | entry | +=======+ | 1 | +-------+ 1 tuple (1.074ms) sql> However, if I call via Mapi I receive an error: SELECT: no such unary operator 'dummy(tinyint)' I'm using the following sequence of API calls: MapiHdl handle = mapi_prepare(connection, "SELECT entry FROM tick.dummy(?)"); int param(0); mapi_param_type(handle, 0, MAPI_INT, MAPI_AUTO, &param); if (mapi_execute(handle) != MOK) { // Error here } The above seems to work fine for a general SELECT statement, but fails for one with a function. Is there a different syntax for calling via Mapi? Iain

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[MonetDB-users] ENUM style table with JOIN versus automatically deduplicated VARCHAR
by Stefan de Konink 02 Jan '12

02 Jan '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi, MonetDB 'deduplicates' strings, is there any benchmark that outlines the performance difference of an ENUM with a low number of (string)items versus the use of a VARCHAR field? The technical question would be; Is it more efficient to do: select * from my_table, my_enum where mytable.my_enum_id = my_enum.id and my_enum.name = 'Something'; or select * from my_table where my_enum_varchar = 'something'; I can imagine that the following would out perform a string comparison, but implies hardcoded values. select * from my_table, my_enum where mytable.my_enum_id = hardcoded; Stefan -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEAREKAAYFAk78fnkACgkQYH1+F2Rqwn3BUQCeOUtPIGzcHT1xpnsF4n78BQ/1 JWAAnjnzPeT8D7CtsjYgAiGg/WRIgNbQ =989f -----END PGP SIGNATURE-----

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[MonetDB-users] MonetDB internals, does UPDATE update in place?
by Stefan de Konink 29 Dec '11

29 Dec '11

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi, Just to be very sure; I know that the DELETE, INSERT strategy to update the database will guarantee a database that keeps on growing, because of the lack of VACUUM. Is the normal UPDATE statement for fixed width datatypes in place, or is it also a form of copy-on-write? Stefan -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEAREKAAYFAk78fPwACgkQYH1+F2Rqwn2fxACfWdXvwr4pWODNo4ZH9uq5oVS9 BmwAn16XGh8h/vYsGkvthKej3MA8Nyvi =KK5T -----END PGP SIGNATURE-----

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[MonetDB-users] Maximum size for SQL command in mclient
by Charalampos Nikolaou 28 Dec '11

28 Dec '11

Hi, is there a maximum size for an SQL command (e.g., INSERT INTO statement) that is imposed in mclient? The connection is terminated when I execute several commands from a sql file one of which is quite long. The point where I get the error is at the 8192th byte (which is the last of 8KBs). Babis

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