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  • How to manage db connections on server?

    - by simpatico
    I have a severe problem with my database connection in my web application. Since I use a single database connection for the whole application from singleton Database class, if i try concurrent db operations (two users) the database rollsback the transactions. This is my static method used: All threads/servlets call static Database.doSomething(...) methods, which in turn call the the below method. private static /* synchronized*/ Connection getConnection(final boolean autoCommit) throws SQLException { if (con == null) { con = new MyRegistrationBean().getConnection(); } con.setAutoCommit(true); //TODO return con; } What's the recommended way to manage this db connection/s I have, so that I don't incurr in the same problem.

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  • unique constraint (w/o Trigger) on "one-to-many" relation

    - by elgcom
    To illustrate the problem, I make an example: A tag_bundle consists of one or more than one tags. A unique tag combination can map to a unique tag_bundle, vice versa. tag_bundle tag tag_bundle_relation +---------------+ +--------+ +---------------+--------+ | tag_bundle_id | | tag_id | | tag_bundle_id | tag_id | +---------------+ +--------+ +---------------+--------+ | 1 | | 100 | | 1 | 100 | +---------------+ +--------+ +---------------+--------+ | 101 | | 1 | 101 | +--------+ +---------------+--------+ There can't be another tag_bundle having the combination from tag 100 and tag 101. How can I ensure such unique constraint when executing SQL "concurrently"!! that is, to prevent concurrently adding two bundles with the same tag combination Adding a simple unique constraint on any table does not work, Is there any solution other than Trigger or explicit lock. I come to only this simple way: make tag combination into string, and let it be unique. tag_bundle (unique on tags) tag tag_bundle_relation +---------------+--------+ +--------+ +---------------+--------+ | tag_bundle_id | tags | | tag_id | | tag_bundle_id | tag_id | +---------------+--------+ +--------+ +---------------+--------+ | 1 | 100,101| | 100 | | 1 | 100 | +---------------+--------+ +--------+ +---------------+--------+ | 101 | | 1 | 101 | +--------+ +---------------+--------+ but it seems not a good way :(

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  • Postgres : Post statement (or insert) asynchronous, non-blocking processing.

    - by Hassan Syed
    I'm wondering if it is possible, that after a collection of rows is inserted, to initiate an operation that is executed asynchronously, is non-blocking, and doesn't need to inform the originator of the request - of the result. I am working with large amounts of events and I can guarantee that the post-insert logic will not fail -- I just want to have a single insert thread in my event-sources, and I want this thread to keep flying without blocking, and without being responsible for any post-delivery book-keeping. I can tell you that I would potentially have a 100 of these jobs executing concurrently and each job might operate on 5 tables with anywhere between 200-1000 inserts on each of these tables. A hint in the right direction should be enough.

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  • Why is this postgres function failing only on one specifc database?

    - by Ollie Edwards
    I'm trying to fix an issue with a legacy database. The quote_literal function is not working for a specific database on an 8.4 install of postgres. Here's my results on a fresh test database: select quote_literal(42); quote_literal --------------- '42' (1 row) And now the same on the target db select quote_literal(42); ERROR: function quote_literal(integer) is not unique LINE 1: select quote_literal(42); ^ HINT: Could not choose a best candidate function. You might need to add explicit type casts. AIUI, the quote_literal(anyvalue) function should handle integer values ok, and this seems to be upheld by the first test. So I figured the quote_literal function must have been overridden in this db but no this doesn't seem to be the case. I could override it with a specific quote_literal(integer) function but I don't see why I should have to. The question is what is could be causing the failure of this function in this specific database whilst not affecting the fresh db?

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  • Is this postgres function cost efficient or still have to clean

    - by kiranking
    There are two tables in postgres db. english_all and english_glob First table contains words like international,confidential,booting,cooler ...etc I have written the function to get the words from english_all then perform for loop for each word to get word list which are not inserted in anglish_glob table. Word list is like I In Int Inte Inter .. b bo boo boot .. c co coo cool etc.. for some reason zwnj(zero-width non-joiner) is added during insertion to english_all table. But in function I am removing that character with regexp_replace. Postgres function for_loop_test is taking two parameter min and max based on that I am selecting words from english_all table. function code is like DECLARE inMinLength ALIAS FOR $1; inMaxLength ALIAS FOR $2; mviews RECORD; outenglishListRow english_word_list;--custom data type eng_id,english_text BEGIN FOR mviews IN SELECT id,english_all_text FROM english_all where wlength between inMinLength and inMaxLength ORDER BY english_all_text limit 30 LOOP FOR i IN 1..char_length(regexp_replace(mviews.english_all_text,'(?)$','')) LOOP FOR outenglishListRow IN SELECT distinct on (regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','')) mviews.id, regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','') where regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','') not in(select english_glob.english_text from english_glob where i=english_glob.wlength) order by regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','') LOOP RETURN NEXT outenglishListRow; END LOOP; END LOOP; END LOOP; END; Once I get the word list I will insert that into another table english_glob. My question is is there any thing I can add to or remove from function to make it more efficient. edit Let assume english_all table have words like footer,settle,question,overflow,database,kingdom If inMinLength = 5 and inmaxLength=7 then in the outer loop footer,settle,kingdom will be selected. For above 3 words inner two loop will apply to get words like f,fo,foo,foot,foote,footer,s,se,set,sett,settl .... etc. In the final process words which are bold will be entered into english_glob with another parameter like 1 to denote it is a proper word and stored in the another filed of english_glob table. Remaining word will be stored with another parameter 0 because in the next call words which are saved in database should not be fetched again. edit2: This is a complete code CREATE TABLE english_all ( id serial NOT NULL, english_all_text text NOT NULL, wlength integer NOT NULL, CONSTRAINT english_all PRIMARY KEY (id), CONSTRAINT english_all_kan_text_uq_id UNIQUE (english_all_text) ) CREATE TABLE english_glob ( id serial NOT NULL, english_text text NOT NULL, is_prop integer default 1, CONSTRAINT english_glob PRIMARY KEY (id), CONSTRAINT english_glob_kan_text_uq_id UNIQUE (english_text) ) insert into english_all(english_text) values ('ant'),('forget'),('forgive'); on function call with parameter 3 and 6 fallowing rows should fetched a an ant f fo for forg forge forget next is insert to another table based on above row insert into english_glob(english_text,is_prop) values ('a',1),('an',1), ('ant',1),('f',0), ('fo',0),('for',1), ('forg',0),('forge',1), ('forget',1), on function call next time with parameter 3 and 7 fallowing rows should fetched.(because f,fo,for,forg are all entered in english_glob table) forgi forgiv forgive

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  • Get the last N rows in the database in order?

    - by Kristopher
    Let's say I have the following database table: record_id | record_date | record_value -----------+-------------+-------------- 1 | 2010-05-01 | 195.00 2 | 2010-07-01 | 185.00 3 | 2010-09-01 | 175.00 4 | 2010-05-01 | 189.00 5 | 2010-06-01 | 185.00 6 | 2010-07-01 | 180.00 7 | 2010-08-01 | 175.00 8 | 2010-09-01 | 170.00 9 | 2010-10-01 | 165.00 I want to grab the last 5 rows with the data ordered by record_date ASC. This is easy to do with: SELECT * FROM mytable ORDER BY record_date ASC LIMIT 5 OFFSET 4 Which would give me: record_id | record_date | record_value -----------+-------------+-------------- 6 | 2010-07-01 | 180.00 7 | 2010-08-01 | 175.00 3 | 2010-09-01 | 175.00 8 | 2010-09-01 | 170.00 9 | 2010-10-01 | 165.00 But how do I do this when I don't know how many records there are and can't compute the magic number of 4? I've tried this query, but if there are less than 5 records, it results in a negative OFFSET, which is invalid: SELECT * FROM mytable ORDER BY record_date ASC LIMIT 5 OFFSET (SELECT COUNT(*) FROM mytable) - 5; So how do I accomplish this?

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  • Check value at insert

    - by ThreeFingerMark
    Hello, i have this three tables. Table: Item Columns: ItemID, Title, Content, NoChange (Date) Table: Tag Columns: TagID, Title Table: ItemTag Columns: ItemID, TagID In the Item Table is a Field with NoChange, if this field = true no Tag is allowed to insert a ItemTag value with this ItemID. How can i check this in the insert? For Updates i have this Statement: UPDATE ItemTag SET TagID = ? where ItemID = ? AND TagID = ? AND exists ( select ItemID from Item where ItemID = ? AND NoChange is null)"); Thank you.

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  • Postgres vs Firebird

    - by Tedi
    I'm looking to use either Firebird or Postgres in my next development project ... largely because both are available under a BSD-like license. I found a great comparison of the two database at http://www.amsoftwaredesign.com/pg_vs_fb But this comparison is a good 2+ years old and both databases have come a long ways since. Does anyone mind updating the comparison table to be relevant for the current versions of both Firebird and Postgres ... or have a link to a site that does a good recent comparison between the two database?

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  • Check if row already exists, if so tell the referenced table the id

    - by flhe
    Let's assume I have a table magazine: CREATE TABLE magazine ( magazine_id integer NOT NULL DEFAULT nextval(('public.magazine_magazine_id_seq'::text)::regclass), longname character varying(1000), shortname character varying(200), issn character varying(9), CONSTRAINT pk_magazine PRIMARY KEY (magazine_id) ); And another table issue: CREATE TABLE issue ( issue_id integer NOT NULL DEFAULT nextval(('public.issue_issue_id_seq'::text)::regclass), number integer, year integer, volume integer, fk_magazine_id integer, CONSTRAINT pk_issue PRIMARY KEY (issue_id), CONSTRAINT fk_magazine_id FOREIGN KEY (fk_magazine_id) REFERENCES magazine (magazine_id) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE NO ACTION ); Current INSERTS: INSERT INTO magazine (longname,shotname,issn) VALUES ('a long name','ee','1111-2222'); INSERT INTO issue (fk_magazine_id,number,year,volume) VALUES (currval('magazine_magazine_id_seq'),'8','1982','6'); Now a row should only be inserted into 'magazine', if it does not already exist. However if it exists, the table 'issue' needs to get the 'magazine_id' of the row that already exists in order to establish the reference. How can i do this? Thx in advance!

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  • expand a varchar column very slowly , why?

    - by francs
    Hi We need to modify a column of a big product table , usually normall ddl statments will be excutely fast ,but the above ddl statmens takes about 10 minnutes?I wonder know the reason! I just want to expand a varchar column?The following is the detailsl --table size wapreader_log= select pg_size_pretty(pg_relation_size('log_foot_mark')); pg_size_pretty ---------------- 5441 MB (1 row) --table ddl wapreader_log= \d log_foot_mark Table "wapreader_log.log_foot_mark" Column | Type | Modifiers -------------+-----------------------------+----------- id | integer | not null create_time | timestamp without time zone | sky_id | integer | url | character varying(1000) | refer_url | character varying(1000) | source | character varying(64) | users | character varying(64) | userm | character varying(64) | usert | character varying(64) | ip | character varying(32) | module | character varying(64) | resource_id | character varying(100) | user_agent | character varying(128) | Indexes: "pk_log_footmark" PRIMARY KEY, btree (id) --alter column wapreader_log= \timing Timing is on. wapreader_log= ALTER TABLE wapreader_log.log_foot_mark ALTER column user_agent TYPE character varying(256); ALTER TABLE Time: 603504.835 ms

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  • Determining the popularity of a video with ratings and views

    - by user295825
    I am about to embark on a new project - a video website. Users will be able to register, and vote on videos by clicking "like" or "dislike", or something to that effect. In any event, it will be a 2-option voting system, not a 5-star system. Every X number of days, I will be generating a "chart" of the most popular videos. So my question is: how should I determine the popularity of a given video? If I went the route of tallying up the videos with the most views, this could have the effect of exceptionally bad videos making it to the of the charts (just because they're so bad). If I go the route of a scoring system based on the amount of "like" and "dislike" votes (eg. 100 like votes, and 50 dislike votes equals a score of 2), videos with few views could appear on the top of the charts. So, what I need to do is a combination of the two. Barring, of course, spammy views and votes. What's your guys' thoughts on the subject?

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  • PostGres if query?

    - by KnockKnockWhosThere
    Is there a way to select records based using an if statement? My table looks like this: id | num | dis 1 | 4 | 0.5234333 2 | 4 | 8.2234 3 | 8 | 2.3325 4 | 8 | 1.4553 5 | 4 | 3.43324 And I want to select the num and dis where dis is the lowest number... So, a query that will produce the following results: id | num | dis 1 | 4 | 0.5234333 4 | 8 | 1.4553

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  • Postgesql select from 2 tables. Joins?

    - by Daniel
    I have 2 tables that look like this: Table "public.phone_lists" Column | Type | Modifiers ----------+-------------------+-------------------------------------------------------------------- id | integer | not null default nextval(('"phone_lists_id_seq"'::text)::regclass) list_id | integer | not null sequence | integer | not null phone | character varying | name | character varying | and Table "public.email_lists" Column | Type | Modifiers ---------+-------------------+-------------------------------------------------------------------- id | integer | not null default nextval(('"email_lists_id_seq"'::text)::regclass) list_id | integer | not null email | character varying | I'm trying to get the list_id, phone, and emails out of the tables in one table. I'm looking for an output like: list_id | phone | email ---------+-------------+-------------------------------- 0 | | [email protected] 0 | | [email protected] 0 | | [email protected] 0 | | [email protected] 0 | | [email protected] 1 | 15555555555 | 1 | 15555551806 | 1 | 15555555508 | 1 | 15055555506 | 1 | 15055555558 | 1 | | [email protected] 1 | | [email protected] I've come up with select pl.list_id, pl.phone, el.email from phone_lists as pl left join email_lists as el using (list_id); but thats not quite right. Any suggestions?

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  • INSERT data from Textbox to Postgres SQL

    - by user1479013
    I just learn how to connect C# and PostgresSQL. I want to INSERT data from tb1(Textbox) and tb2 to database. But I don't know how to code My previous code is SELECT from database. this is my code private void button1_Click(object sender, EventArgs e) { bool blnfound = false; NpgsqlConnection conn = new NpgsqlConnection("Server=127.0.0.1;Port=5432;User Id=postgres;Password=admin123;Database=Login"); conn.Open(); NpgsqlCommand cmd = new NpgsqlCommand("SELECT * FROM login WHERE name='" + tb1.Text + "' and password = '" + tb2.Text + "'",conn); NpgsqlDataReader dr = cmd.ExecuteReader(); if (dr.Read()) { blnfound = true; Form2 f5 = new Form2(); f5.Show(); this.Hide(); } if (blnfound == false) { MessageBox.Show("Name or password is incorrect", "Message Box", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1); dr.Close(); conn.Close(); } } So please help me the code.

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  • Backup of folder + database - Python

    - by RadiantHex
    Hi there, I feel like this is quite delicate, I have various folders whith projects I would like to backup into a zip/tar file, but would like to avoid backing up files such as pyc files and temporary files. I also have a Postgres db I need to backup. Any tips for running this operation as a python script? Also, would there be anyway to stop the process from hogging resources in the process? Help would be very much appreciated.

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  • Add all lines multiplied by another line in another table

    - by russell
    Hi, I hope I can explain this good enough. I have 3 tables. wo_parts, workorders and part2vendor. I am trying to get the cost price of all parts sold in a month. I have this script. $scoreCostQuery = "SELECT SUM(part2vendor.cost*wo_parts.qty) as total_score FROM part2vendor INNER JOIN wo_parts ON (wo_parts.pn=part2vendor.pn) WHERE workorder=$workorder"; What I am trying to do is each part is in wo_parts (under partnumber [pn]). The cost of that item is in part2vendor (under part number[pn]). I need each part price in part2vendor to be multiplied by the quantity sold in wo_parts. The way all 3 tie up is workorders.ident=wo_parts.workorder and part2vendor.pn=wo_parts.pn. I hope someone can assist. The above script does not give me the same total as when added by calculator.

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  • INSERT and transaction searilization in PostreSQL

    - by Alexander
    Hello! I have a question. Transaction isolation level set to serializable. When the one user open transaction and INSERT or UPDATE data in "table1" and then another user open transaction and try to INSERT data to the same table is second user need to wait 'til the first user commits the transaction?

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  • Paginating data, has to be a better way

    - by John Tyler
    I've read like 10 or so "tutorials", and they all involve the same thing: Pull a count of the data set Pull the relevant data set (LIMIT, OFFSET) IE: SELECT COUNT(*) FROM table WHERE something = ? SELECT * FROM table WHERE something =? LIMIT ? offset ?` Two very similar queries, no? There has to be a better way to do this, my dataset is 600,000+ rows and already sluggish (results are determined by over 30 where clauses, and vary from user to user, but are properly indexed of course).

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  • How can I selectively override a django .count() method

    - by Tom Viner
    I'm using postGresSQL and my main table has about 20,000 rows. Sometimes count() methods can take ages or even timeout. Mod.manager.filter(...).count() I need to selectively override the count() method depending on what filter has been applied. Just having a cache of results would be a great gain but I'd like to be able to say: if filter query is just {'enabled'=True} then return 20,000 without touching the db. Note: I can't prevent the call to .count() as it's inside django's pagination, which always does a count.

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  • PropelBundle database:create for postgres

    - by Karol85
    I've installed propel bundle for symfony2. my database configuration is: propel: dbal: driver: pgsql user: postgres password: postgres dsn: pgsql:host=localhost;port=5432;dbname=test_database options: {} attributes: {} When i wan to create this database from console (console propel: database:create) i have got strange error : Unable to open PDO connection [wrapped: SQLSTATE[08006] [7] FATAL: database "pgsql" does not exist. i created pgsql database on my localhost and everything was good. Database "test_database" was succesfull created. Can somebody explain me why i got this previous error? On mysql i've created database without any problems.

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  • Error when pushing data to Heroku: time zone displacement out of range

    - by J. Pablo Fernández
    I run the following command to push the contents of my local database to Heroku: heroku db:push --app my-app and from my home computer it works flawlessly but from my work computer I get this error: Taps Server Error: PGError: ERROR: time zone displacement out of range: "2011-11-15 12:00:00.000000+5894114400" I'm not sure where that date is coming from, I can't find it in the data anywhere. Any ideas what's going on and/or how to fix it? Thanks.

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  • PostGres - run a query in batches?

    - by CaffeineIV
    Is it possible to loop through a query so that if (for example) 500,000 rows are found, it'll return results for the first 10,000 and then rerun the query again? So, what I want to do is run a query and build an array, like this: $result = pg_query("SELECT * FROM myTable"); $i = 0; while($row = pg_fetch_array($result) ) { $myArray[$i]['id'] = $row['id']; $myArray[$i]['name'] = $row['name']; $i++; } But, I know that there will be several hundred thousand rows, so I wanted to do it in batches of like 10,000... 1- 9,999 and then 10,000 - 10,999 etc... The reason why is because I keep getting this error: Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 3 bytes) Which, incidentally, I don't understand how 3 bytes could exhaust 512M... So, if that's something that I can just change, that'd be great, although, still might be better to do this in batches?

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