developers-list May 2015

developers-list@monetdb.org

5 participants
4 discussions

Hashjoin performance with large vs small tables

by Roberto Cornacchia

Hi there, Triggered by a suspiciously slow join, I had a look at BATsubjoin, in particular at how it is decided which algorithm to use. I looked at a couple of cases with a join on strings. This is one (pseudo syntax): l.count ~16M l.T.sorted = 0 l.T.revsorted = 0 r.count = 1 r.T.sorted = 1 r.T.revsorted = 1 In this case, a hash table on r is created (because it's smaller). This join takes *430ms*. I forced swapping l and r, thus built the hash table on the larger bat, and then it takes *0.8ms*. Notice that though r.count = 1 is a bit of an extreme case, it does happen often in practice. And the case with a few tuples would not be very different. The question I wanted to ask is: is it always right to build the hash table on the small table? Perhaps some more heuristics can help? Like: if the smaller is very small, and the larger is not extremely large, then hash on the larger one? Roberto

7 years, 2 months

Facing issues in implementing Embedded R in MonetDB-11.19.11

by Vishal Virmani

Hi I am implementing Embedded R in MonetDB version 11.19.11. My environment is VM with Ubuntu 14.04 Server. I have build MonetDB from source and R as well as from source. Running the command sudo mserver5 --version shows me the desired output. When i try to invoke a database using sudo monetdb start testdb1 command, where testdb1 is a database i successfully created, it repeatedly throws up an error...database 'testdb1' started up, but failed to open up a communication channel. Upon checking the associated merovingian log file i see further messages saying the object code to rapi.prelude missing. Any way to resolve this...? Regards Vishal Virmani @poisoncreed

7 years, 2 months

Suggestion: Windows builds ...

by g4＠novadsp.com

Hello Might it be possible to include copies of the relevant header files for the support libraries (iconv through to zdll) in the GIT repo and/or tarballs? There is a considerable amount of pain involved in acquiring/building/installing matching versions of the lib/dll files on Windows (esp. on Windows!). Also libstream.dll does not advertise any version information which makes matching just that bit harder :) Thanks. Jerry.

7 years, 2 months

Announcement: New Oct2014-SP3 Bugfix release of MonetDB suite

by Sjoerd Mullender

The MonetDB team at CWI/MonetDB BV is pleased to announce the Oct2014-SP3 bugfix release of the MonetDB suite of programs. More information about MonetDB can be found on our website at <http://www.monetdb.org/>. For details on this release, please see the release notes at <http://www.monetdb.org/Downloads/ReleaseNotes>. As usual, the download location is <http://dev.monetdb.org/downloads/>. Oct 2014-SP3 bugfix release Build Environment * We now also create debug packages for Debian and Ubuntu. MonetDB Common * Replaced the rangejoin implementation with one that uses imprints if it can. Bug Fixes * 3466: UPDATE statements fails with "GDKerror: MT_mremap() failed" * 3602: Surprising overload resolution of generate_series * 3613: SQL data dictionary contains columns names which are also special keywords. This causes unexpected/unneeded SQL query errors * 3645: Network address operators such as << and <<= do not work * 3647: missing BAT for a column leads to crash in gtr_update_delta * 3648: memory corruption on unclean connection shutdown with local temporary tables * 3650: Naming of persistent BATs is fragile * 3653: PREPARE crashes mserver if unbound variable is function parameter * 3655: SQL WHERE -1 in (-1) issue? * 3656: error message after calling fitsload() * 3660: Incorrect Results for Comparison Operators on inet Datatype * 3661: Ship debug symbols for pre-built binaries * 3662: UPDATE row with row value constructor crashes monetdb server * 3663: Incorrect result ROW_NUMBER in subquery * 3664: SQLstatementIntern missing parameter when using jsonstore * 3665: inter-session starvation issue, particularly affects sys.queue * 3666: casting text column to inet truncating text column and resulting inet for first occurrence only * 3667: insert of negative value for oid column aborts mserver5 process with assertion failure * 3669: ALTER TABLE <tbl_nm> ADD CONSTRAINT <tbl_uc1> UNIQUE (col1, col2, col3) causes Assertion failure and abort * 3671: ODBC-Access on Windows 2012 does not work - E_FAIL * 3672: libbat_la-gdk_utils.o: relocation R_X86_64_PC32 against `MT_global_exit' can not be used when making a shared object * 3676: merovingian hangs trying to exit * 3677: Crash in BATgroup_internal (caused by 87379087770d?) * 3678: Ruby driver installation ignores prefix * 3680: Prepared statements fail on execution with message 'Symbol type not found' * 3684: Wrong query result set WHERE "IS NULL" or "NOT IN" clauses uses in combination with ORDER, LIMIT and OFFSET * 3687: 'bat.insert' undefined * 3688: Crash at exit (overrun THRerrorcount?) * 3689: No more connections accepted if a single client misbehaves * 3690: find_fk: Assertion `t && i' failed. * 3691: conversion of whitespaces string to double or float is accepted without an error during insert * 3693: algebra.join undefined (caused by non-existing variables in the plan) * 3696: Inconsistent behavior between dbl (SQL double) and flt (SQL real) data types and across platforms * 3697: mserver5[26946]: segfault at 0 ip 00007f3d0e1ab808 sp 00007f3cefbfcad0 error 4 in lib_sql.so[7f3d0e180000+16c000] * 3699: segfault again! (during last week I found 3 segfault bugs already) * 3703: INSERT INTO a MERGE TABLE crashes mserver5 * 3704: Unknown identifier from subquery * 3705: Assertion failure in rel_bin.c:2274: rel2bin_project: Assertion `0' failed. * 3706: Assertion failure in gdk_bat.c: BATassertHeadProps: Assertion `!b->H->sorted || cmp <= 0' failed. * 3709: "BATproject: does not match always" on abusive use of ALTER TABLE SET READ ONLY

7 years, 2 months

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developers-list May 2015