May 2015 - users-list

[MonetDB-users] Books CDs
by CHARTS LICENSING 11 Aug '24

11 Aug '24

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Multi-column update based on joined table
by Lee Hachadoorian 11 Aug '24

11 Aug '24

I need to update multiple columns (~250) from one table to another based on a two-column key. In Postgres I would write this using the FROM clause, but since MonetDB doesn't support the FROM clause, I've successfully updated one column with: UPDATE census.acs2010_5yr SET b07401001 = ( SELECT CAST(b07401001 AS int) FROM acs2010_5yr.tmp_seq0001 WHERE acs2010_5yr.stusab = tmp_seq0001.stusab AND acs2010_5yr.logrecno = tmp_seq0001.logrecno ); My question is whether there is any benefit to writing a multiple column update into a single UPDATE statement: UPDATE target_table SET column1 = (SELECT column1 FROM source_table WHERE target_table.key = source_table.key), column2 = (SELECT column2 FROM source_table WHERE target_table.key = source_table.key), ..., columnN = (SELECT columnN FROM source_table WHERE target_table.key = source_table.key); On Postgres I believe the multi-column update using a table join would only have to do the sequential scan of each table once, but with the necessity of sub-selects in MonetDB, what is the backend doing? Is it already doing an index scan once for each row in the single column case, then doing it once for each row * column in the multi-column case? Best, --Lee -- Lee Hachadoorian Asst Professor of Geography, Dartmouth College http://freecity.commons.gc.cuny.edu/

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[MonetDB-users] XQuery API and XLink/XUpdate support
by Alexandra Mart�nez 27 Jun '24

27 Jun '24

Hello all, I was wondering if there is any documentation about the API for XQuery (i.e., how to write xqueries from a Java program). Also, I am interested in using some features of XLink and XUpdate on top of my XML database. Is support for any of these in progress? Thanks in advance, Alexandra ______________________________________________________ Click here to donate to the Hurricane Katrina relief effort. http://store.yahoo.com/redcross-donate3/

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[MonetDB-users] Proofreading your professional documents
by Richard Hounslow 24 Feb '24

24 Feb '24

Dear Professor/Lecturer Please excuse us for contacting you directly. We are offering an efficient service to help you ensure your academic and professional work is written in perfect English. We will check the grammar and style of your work and return it to you to meet your requirements and deadlines. Proof-Reading-Service.com can provide you with a professional proofreading service at a very reasonable rate. All our proofreaders are highly qualified native English speakers. Many work as leading academics in their fields and all have extensive experience of proofreading to the highest standards. If you are interested in our service, please take a look at our website: www.proof-reading-service.com All you have to do is send us your document as a word attachment with the deadline and we will guarantee delivery of a perfectly written document to give you complete confidence when you submit your work. The fee is worked out on a flat rate (£6.95 per thousand words or 0.695 pence per word), so you know exactly how much the proofreading will cost in advance. Once we have received your document(s) we will confirm the word count, the price and the deadline. If you have not heard from us within 2 hours during normal business hours after you have sent your work please resend it from a different email account or send the file to proofreadings(a)gmail.com. We look forward to hearing from you! Yours faithfully Proof-Reading-Service.com

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Cluster advantages MonetDB
by Luciano Sasso 15 Jul '15

15 Jul '15

Hi, What the cluster Advantages MonetDB, If a query in shard tables in a cluster can not be ordered, what the advantage of using a MonetDB cluster? besides the replication in case of failure. Att, -- Luciano Sasso Vieira Data Scientist & Solutions Architect luciano(a)gsgroup.com.br <http://www.gsgroup.com.br> | tel: 17 3353-0833 | cel: 17 99706-9335 www.gsgroup.com.br <http://www.gsgroup.com.br> --- Este email foi escaneado pelo Avast antivírus. http://www.avast.com

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Concurrency test causes crash of MonetDB 5 server
by michael.witt＠uniserv.com 30 Jun '15

30 Jun '15

Hi, we experience a crash of MonetDB 5 server during tests of a multi-threaded client access via JDBC-Driver and MapiSocket: The application is already optimized to avoid "concurrency conflicts" because of the "Optimistic Concurrency Control" concept. The test simulates client access via two threads. All update operations (INSERT, UPDATE, DELETE, DROP TABLE, CREATE TABLE) are done in serial. All read operations are done in parallel to other read operations or to update operations. The test causes a crash of mserver5.exe after a few minutes. If the test uses just one thread, all read and update operations are done in serial and the server does not crash. What is the rule of thumb to avoid crashes when using several client threads? Crash details: Problem signature: Problem Event Name: APPCRASH Application Name: mserver5.exe Application Version: 0.0.0.0 Application Timestamp: 55389f58 Fault Module Name: StackHash_8ec6 Fault Module Version: 6.1.7601.18247 Fault Module Timestamp: 521eaf24 Exception Code: c0000374 Exception Offset: 00000000000c4102 OS Version: 6.1.7601.2.1.0.144.8 Locale ID: 1031 Additional Information 1: 8ec6 Additional Information 2: 8ec62499039d1d8234b025a62c725eb7 Additional Information 3: f8f3 Additional Information 4: f8f3e520847c0684b15d4080171779ef # MonetDB 5 server v11.19.9 "Oct2014-SP2" # Serving database 'uniserv', using 4 threads # Compiled for x86_64-pc-winnt/64bit with 64bit OIDs dynamically linked # Found 10.000 GiB available main-memory. .. # MonetDB/SQL module loaded Michael Witt

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1-to-N (bat) UDF
by Roberto Cornacchia 15 Jun '15

15 Jun '15

Hi there, I need a string tokenizer in MonetDB. The problem I have is not with the function itself, but with the fact that this is a 1 to N rows function. Implementing this for a single string value is easy enough, using a table function that takes a string a returns a table: create function tokenize(s string) returns table (token string) external name tokenize; select * from tokenize("one two three"); That's fine. The issue I'm having is with extending this to a column of strings. Ideally, given a string column one two three four five six seven eight I'd like to get an output along these lines (simplistic representation here): one two three | one one two three | two one two three | three four five six | four four five six | five four five six | six seven eight | seven seven eight | eight I can sure code the c function and the mal wrapper to implement this, but I can't see how to map it to SQL, given that table functions don't accept identifiers as parameters. Any idea? Any possible workaround? Thanks, Roberto

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should the SAMPLE command produce random results?
by Anthony Damico 01 Jun '15

01 Jun '15

# here's a reproducible example using R code to repeat the sampling 1000 times. in both SAMPLE examples below, the database pulls the 2 less than 200 times out of 1000. shouldn't it be close to 500 out of 1000? this seems not random (misleading to users?) sorry if i'm misunderstanding something.. thank you!! # start in an empty directory somewhere # setwd( "C:/My Directory/MonetDB" ) # # # # # # # # # START OF SETUP - no editing required library(MonetDB.R) batfile <- monetdb.server.setup( database.directory = paste0( getwd() , "/MonetDB" ) , monetdb.program.path = ifelse( .Platform$OS.type == "windows" , "C:/Program Files/MonetDB/MonetDB5" , "" ) , dbname = "test" , dbport = 50000 ) pid <- monetdb.server.start( batfile ) db <- dbConnect( MonetDB.R() , "monetdb://localhost:50000/test" , wait = TRUE ) # # # END OF SETUP dbGetQuery( db , "SELECT 1 AS col UNION ALL SELECT 2 AS col" ) out <- NULL for ( i in 1:1000 ){ out <- c( out , dbGetQuery( db , "SELECT * FROM ( SELECT 1 AS col UNION ALL SELECT 2 AS col ) AS temp SAMPLE 0.5" ) ) } # not random table( unlist( out ) ) # 1 2 # 880 120 out <- NULL for ( i in 1:1000 ){ out <- c( out , dbGetQuery( db , "SELECT * FROM ( SELECT 1 AS col UNION ALL SELECT 2 AS col ) AS temp SAMPLE 1" ) ) } # ALSO not random table( unlist( out ) ) # 1 2 # 856 144

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a few performance improvement questions
by Anthony Damico 29 May '15

29 May '15

hi, i've been running some pretty big queries on a few tables (total of 900 million records) on a 64GB windows machine and i'm curious if anyone might provide advice about whether any of these strategies are computationally expensive? i am maxing out my available RAM in my queries a lot, and at the point it hits that ceiling, the computation starts dragging. here's my pseudo-sql that displays the kinds of commands i've been running. thanks! ============ (a) i am conducting a left join where not all records match. the non-matching records need to be zeroes in general, is this the least computationally demanding way to get an average amount per person, including the zeroes? SELECT AVG( sum_amount ) AS avg_amt_per_person FROM ( SELECT person_id , SUM( CASE WHEN amount IS NULL THEN 0 ELSE amount END ) AS sum_amount FROM ( ( SELECT person_id FROM person_table ) AS a LEFT JOIN ( SELECT person_id , amount FROM amount_table ) AS b ON a.person_id = b.person_id ) AS temp_table GROUP BY person_id ) ; ============ (b) i am on windows (so no strptime) and i have dates in either a mm/dd/yy format but some january thru september are m/dd/yy (i.e. the month can either be one or two digits). i am just calculating the month as part of my query on-the-fly. is it foolish of me not to add a new, permanent column to the data set? i don't have a good sense of whether this segment slows down my query by a lot. it is one of my join/merge variables. CAST( CASE WHEN SUBSTRING( some_date , 2 , 1 ) = '/' THEN SUBSTRING( some_date , 1 , 1 ) ELSE SUBSTRING( some_date , 1 , 2 ) END AS DOUBLE ) AS some_month ============ (c) i have a three tables that have the same structure that get LEFT JOINed onto my main table. so right now i am doing something like-- main_table LEFT JOIN second_table LEFT JOIN third_table LEFT JOIN fourth_table is it smarter fo me to do this instead? -- CREATE TABLE stacked_table FROM second_table UNION ALL third_table UNION ALL fourth_table main_table LEFT JOIN stacked_table

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is bugzilla down?
by Anthony Damico 27 May '15

27 May '15

https://www.monetdb.org/bugzilla/ connection times out -- from computers in three countries.

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