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  • Why MySQL multiple-column index is overpopulated?

    - by actual
    Consider following MySQL table: CREATE TABLE `log` ( `what` enum('add', 'edit', 'remove') CHARACTER SET ascii COLLATE ascii_bin NOT NULL, `with` int(10) unsigned NOT NULL, KEY `with_what` (`with`,`what`) ) ENGINE=InnoDB; INSERT INTO `log` (`what`, `with`) VALUES ('add', 1), ('edit', 1), ('add', 2), ('remove', 2); As I understand, with_what index must have 2 unique entries on its first with level and 3 unique entries in what "subindex". But MySQL reports 4 unique entries for each level. In other words, number of unique elements for each level is always equal to number of rows in log table. Is that a bug, a feature or my misunderstanding?

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  • oracle index for string column - does format of data affects quality of index?

    - by Jayan
    We have following type of "Unique ID" column for many tables in the database (Oracle). It is a string with following format <randomnumber>-<ascendingnumber>-<machinename> So we have some thing like this U1234-12345-NBBJD U1234-12346-NBBJD U1234-12347-NBBJD U1234-12348-NBBJD U1234-12349-NBBJD The UID value is unique, we have unique index on them. Does the following format is more efficient than above for index scans? NBBJD-U1234-12345 NBBJD-U1234-12346 NBBJD-U1234-12347 NBBJD-U1234-12348 NBBJD-U1234-12349

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  • cakephp isUnique for 2 fields?

    - by jodeci
    I have a registration form in which users can fill in two email address (email1 & email2). Marketing's requirement is that they need to be unique (unique as in if we had 10 users, then there would be 10*2=20 unique email address). The system is already built on cakephp, so what I'd like to know is, is there something similar to the isUnique feature (unique in one field) that can do this right out of the box? Or am I doomed to code this myself? Thanks in advance.

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  • Cleaner way to store to replace a scalar hash value with an array ref?

    - by user275455
    I am building a hash where the keys, associated with scalars, are not necessarily unique. I want the desired behavior to be that if the key is unique, the value is the scalar. If the key is not unique, I want the value to be an array reference of the scalars associated witht the key. Since the hash is built up iteratively, I don't know if the key is unique ahead of time. Right now, I am doing something like this: if(!defined($hash{$key})){ $hash{$key} = $val; } elseif(ref($hash{$key}) ne 'ARRAY'){ my @a; push(@a, $hash{$key}); push(@, $val); $hash{$key} = \@a; } else{ push(@{$hash{$key}}, $val); } Is there a simpler way to do this?

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  • Index a mysql table of 3 integer fields

    - by Doori Bar
    I have a mysql table of 3 integer fields. None of the fields have a unique value - but the three of them combined are unique. When I query this table, I only search by the first field. Which approach is recommended for indexing such table? Having a multiple-field primary key on the 3 fields, or setting an index on the first field, which is not unique? Thanks, Doori Bar

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  • So…is it a Seek or a Scan?

    - by Paul White
    You’re probably most familiar with the terms ‘Seek’ and ‘Scan’ from the graphical plans produced by SQL Server Management Studio (SSMS).  The image to the left shows the most common ones, with the three types of scan at the top, followed by four types of seek.  You might look to the SSMS tool-tip descriptions to explain the differences between them: Not hugely helpful are they?  Both mention scans and ranges (nothing about seeks) and the Index Seek description implies that it will not scan the index entirely (which isn’t necessarily true). Recall also yesterday’s post where we saw two Clustered Index Seek operations doing very different things.  The first Seek performed 63 single-row seeking operations; and the second performed a ‘Range Scan’ (more on those later in this post).  I hope you agree that those were two very different operations, and perhaps you are wondering why there aren’t different graphical plan icons for Range Scans and Seeks?  I have often wondered about that, and the first person to mention it after yesterday’s post was Erin Stellato (twitter | blog): Before we go on to make sense of all this, let’s look at another example of how SQL Server confusingly mixes the terms ‘Scan’ and ‘Seek’ in different contexts.  The diagram below shows a very simple heap table with two columns, one of which is the non-clustered Primary Key, and the other has a non-unique non-clustered index defined on it.  The right hand side of the diagram shows a simple query, it’s associated query plan, and a couple of extracts from the SSMS tool-tip and Properties windows. Notice the ‘scan direction’ entry in the Properties window snippet.  Is this a seek or a scan?  The different references to Scans and Seeks are even more pronounced in the XML plan output that the graphical plan is based on.  This fragment is what lies behind the single Index Seek icon shown above: You’ll find the same confusing references to Seeks and Scans throughout the product and its documentation. Making Sense of Seeks Let’s forget all about scans for a moment, and think purely about seeks.  Loosely speaking, a seek is the process of navigating an index B-tree to find a particular index record, most often at the leaf level.  A seek starts at the root and navigates down through the levels of the index to find the point of interest: Singleton Lookups The simplest sort of seek predicate performs this traversal to find (at most) a single record.  This is the case when we search for a single value using a unique index and an equality predicate.  It should be readily apparent that this type of search will either find one record, or none at all.  This operation is known as a singleton lookup.  Given the example table from before, the following query is an example of a singleton lookup seek: Sadly, there’s nothing in the graphical plan or XML output to show that this is a singleton lookup – you have to infer it from the fact that this is a single-value equality seek on a unique index.  The other common examples of a singleton lookup are bookmark lookups – both the RID and Key Lookup forms are singleton lookups (an RID lookup finds a single record in a heap from the unique row locator, and a Key Lookup does much the same thing on a clustered table).  If you happen to run your query with STATISTICS IO ON, you will notice that ‘Scan Count’ is always zero for a singleton lookup. Range Scans The other type of seek predicate is a ‘seek plus range scan’, which I will refer to simply as a range scan.  The seek operation makes an initial descent into the index structure to find the first leaf row that qualifies, and then performs a range scan (either backwards or forwards in the index) until it reaches the end of the scan range. The ability of a range scan to proceed in either direction comes about because index pages at the same level are connected by a doubly-linked list – each page has a pointer to the previous page (in logical key order) as well as a pointer to the following page.  The doubly-linked list is represented by the green and red dotted arrows in the index diagram presented earlier.  One subtle (but important) point is that the notion of a ‘forward’ or ‘backward’ scan applies to the logical key order defined when the index was built.  In the present case, the non-clustered primary key index was created as follows: CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col ASC) ) ; Notice that the primary key index specifies an ascending sort order for the single key column.  This means that a forward scan of the index will retrieve keys in ascending order, while a backward scan would retrieve keys in descending key order.  If the index had been created instead on key_col DESC, a forward scan would retrieve keys in descending order, and a backward scan would return keys in ascending order. A range scan seek predicate may have a Start condition, an End condition, or both.  Where one is missing, the scan starts (or ends) at one extreme end of the index, depending on the scan direction.  Some examples might help clarify that: the following diagram shows four queries, each of which performs a single seek against a column holding every integer from 1 to 100 inclusive.  The results from each query are shown in the blue columns, and relevant attributes from the Properties window appear on the right: Query 1 specifies that all key_col values less than 5 should be returned in ascending order.  The query plan achieves this by seeking to the start of the index leaf (there is no explicit starting value) and scanning forward until the End condition (key_col < 5) is no longer satisfied (SQL Server knows it can stop looking as soon as it finds a key_col value that isn’t less than 5 because all later index entries are guaranteed to sort higher). Query 2 asks for key_col values greater than 95, in descending order.  SQL Server returns these results by seeking to the end of the index, and scanning backwards (in descending key order) until it comes across a row that isn’t greater than 95.  Sharp-eyed readers may notice that the end-of-scan condition is shown as a Start range value.  This is a bug in the XML show plan which bubbles up to the Properties window – when a backward scan is performed, the roles of the Start and End values are reversed, but the plan does not reflect that.  Oh well. Query 3 looks for key_col values that are greater than or equal to 10, and less than 15, in ascending order.  This time, SQL Server seeks to the first index record that matches the Start condition (key_col >= 10) and then scans forward through the leaf pages until the End condition (key_col < 15) is no longer met. Query 4 performs much the same sort of operation as Query 3, but requests the output in descending order.  Again, we have to mentally reverse the Start and End conditions because of the bug, but otherwise the process is the same as always: SQL Server finds the highest-sorting record that meets the condition ‘key_col < 25’ and scans backward until ‘key_col >= 20’ is no longer true. One final point to note: seek operations always have the Ordered: True attribute.  This means that the operator always produces rows in a sorted order, either ascending or descending depending on how the index was defined, and whether the scan part of the operation is forward or backward.  You cannot rely on this sort order in your queries of course (you must always specify an ORDER BY clause if order is important) but SQL Server can make use of the sort order internally.  In the four queries above, the query optimizer was able to avoid an explicit Sort operator to honour the ORDER BY clause, for example. Multiple Seek Predicates As we saw yesterday, a single index seek plan operator can contain one or more seek predicates.  These seek predicates can either be all singleton seeks or all range scans – SQL Server does not mix them.  For example, you might expect the following query to contain two seek predicates, a singleton seek to find the single record in the unique index where key_col = 10, and a range scan to find the key_col values between 15 and 20: SELECT key_col FROM dbo.Example WHERE key_col = 10 OR key_col BETWEEN 15 AND 20 ORDER BY key_col ASC ; In fact, SQL Server transforms the singleton seek (key_col = 10) to the equivalent range scan, Start:[key_col >= 10], End:[key_col <= 10].  This allows both range scans to be evaluated by a single seek operator.  To be clear, this query results in two range scans: one from 10 to 10, and one from 15 to 20. Final Thoughts That’s it for today – tomorrow we’ll look at monitoring singleton lookups and range scans, and I’ll show you a seek on a heap table. Yes, a seek.  On a heap.  Not an index! If you would like to run the queries in this post for yourself, there’s a script below.  Thanks for reading! IF OBJECT_ID(N'dbo.Example', N'U') IS NOT NULL BEGIN DROP TABLE dbo.Example; END ; -- Test table is a heap -- Non-clustered primary key on 'key_col' CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col) ) ; -- Non-unique non-clustered index on the 'data' column CREATE NONCLUSTERED INDEX [IX dbo.Example data] ON dbo.Example (data) ; -- Add 100 rows INSERT dbo.Example WITH (TABLOCKX) ( key_col, data ) SELECT key_col = V.number, data = V.number FROM master.dbo.spt_values AS V WHERE V.[type] = N'P' AND V.number BETWEEN 1 AND 100 ; -- ================ -- Singleton lookup -- ================ ; -- Single value equality seek in a unique index -- Scan count = 0 when STATISTIS IO is ON -- Check the XML SHOWPLAN SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 32 ; -- =========== -- Range Scans -- =========== ; -- Query 1 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col <= 5 ORDER BY E.key_col ASC ; -- Query 2 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col > 95 ORDER BY E.key_col DESC ; -- Query 3 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 10 AND E.key_col < 15 ORDER BY E.key_col ASC ; -- Query 4 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 20 AND E.key_col < 25 ORDER BY E.key_col DESC ; -- Final query (singleton + range = 2 range scans) SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 10 OR E.key_col BETWEEN 15 AND 20 ORDER BY E.key_col ASC ; -- === TIDY UP === DROP TABLE dbo.Example; © 2011 Paul White email: [email protected] twitter: @SQL_Kiwi

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  • Solr Multicore Admin Problem

    - by Daniel M
    Im trying to add a url based security constraint to solr deployed in websphere 6.1. If I specify the core name in the url of the constraint then the admin url for that core gives a 404. Has anyone had any success with this or any suggestions? Cheers Cross-posted with stackoverflow

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  • Hibernate: @UniqueConstraint with @ManyToOne field???

    - by Misha Koshelev
    Dear All: Using the following code: @Entity @Table(uniqueConstraints=[@UniqueConstraint(columnNames=["account","name"])]) class Friend { @Id @GeneratedValue(strategy=GenerationType.AUTO) public Long id @ManyToOne public Account account public String href public String name } I get the following error: org.hibernate.AnnotationException: Unable to create unique key constraint (account, name) on table Friend: account not found It seems this has to do with the @ManyToOne constraint, which I imagine actually creates a separate UniqueConstraint??? In any case, if I take this out, there is no complaint about the UniqueConstraint, but there is another error which makes me believe it must be left in. org.hibernate.MappingException: Could not determine type for: com.mksoft.fbautomate.domain.Account, at table: Friend, for columns: [org.hibernate.mapping.Column(account)] Any hints how I can create such a desired constraint (i.e., that each combination of account and name occurs only once???) Thank you! Misha

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  • Fixtures and inheritance in Symfony

    - by Tere
    Hi! I have a database schema in Symfony like this: Persona: actAs: { Timestampable: ~ } columns: primer_nombre: { type: string(255), notnull: true } segundo_nombre: { type: string(255) } apellido: { type: string(255), notnull: true } rut: { type: string(255) } email: { type: string(255) } email2: { type: string(255) } direccion: { type: string(400) } ciudad: { type: string(255) } region: { type: string(255) } pais: { type: string(255) } telefono: { type: string(255) } telefono2: { type: string(255) } fecha_nacimiento: { type: date } Alumno: inheritance: type: concrete extends: Persona columns: comentario: { type: string(255) } estado_pago: { type: string(255) } Alumno_Beca: columns: persona_id: { type: integer, primary: true } beca_id: { type: integer, primary: true } relations: Alumno: { onDelete: CASCADE, local: persona_id, foreign: id } Beca: { onDelete: CASCADE, local: beca_id, foreign: id } Beca: columns: nombre: { type: string(255) } monto: { type: double } porcentaje: { type: double } descripcion: { type: string(5000) } As you see, "alumno" has a concrete inheritance from "persona". Now I'm trying to create fixtures for this two tables, and I can't make Doctrine to load them. It gives me this error: SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (eat/alumno__beca, CONSTRAINT alumno__beca_persona_id_alumno_id FOREIGN KEY (persona_id) REFERENCES alumno (id) ON DELETE CASCADE) Does someone know how to write a fixture for a table inherited from another? Thanks!

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  • What is the proper way to create a recursive entity in the Entity Framework?

    - by Orion Adrian
    I'm currently using VS 2010 RC, and I'm trying to create a model that contains a recursive self-referencing entity. Currently when I import the entity from the model I get an error indicating that the parent property cannot be part of the association because it's set to 'Computed' or 'Identity', though I'm not sure why it does it that way. I've been hand-editing the file to get around that error, but then the model simply doesn't work. What is the proper way to get recursive entities to work in the Entity Framework. CREATE TABLE [dbo].[Appointments]( [AppointmentId] [int] IDENTITY(1,1) NOT NULL, [Description] [nvarchar](1024) NULL, [Start] [datetime] NOT NULL, [End] [datetime] NOT NULL, [Username] [varchar](50) NOT NULL, [RecurrenceRule] [nvarchar](1024) NULL, [RecurrenceState] [varchar](20) NULL, [RecurrenceParentId] [int] NULL, [Annotations] [nvarchar](50) NULL, [Application] [nvarchar](100) NOT NULL, CONSTRAINT [PK_Appointments] PRIMARY KEY CLUSTERED ( [AppointmentId] ASC ) ) GO ALTER TABLE [dbo].[Appointments] WITH CHECK ADD CONSTRAINT [FK_Appointments_ParentAppointments] FOREIGN KEY([RecurrenceParentId]) REFERENCES [dbo].[Appointments] ([AppointmentId]) GO ALTER TABLE [dbo].[Appointments] CHECK CONSTRAINT [FK_Appointments_ParentAppointments] GO

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  • does the order a composite key is defined matter?

    I have a table with (col1,col2) as a composite primary key. create table twokeytable(col1 int,col2 int,constraint twokeytable_pk primary key (col1,col2)); and another table with col3,col4 collumns witha composite foreign key(col3,col4) which references the(col1,col2) primary key. For some processing I need to drop the foreign key and primary constraints .While restoring the constraints does order of the keys matter?. are these same? create table fktwokeytable(col3 int,col4 int,constraint fkaddfaa_fk foreign key(col4,col3) references twokeytable(col1,col2)) and create table fktwokeytable(col3 int,col4 int,constraint fkaddfaa_fk foreign key(col3,col4) references twokeytable(col1,col2))

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  • Converting LDAP from Tomcat to GlassFish

    - by Jon
    Hi, I have a simple web-app that is developed in Netbeans(6.8) and works fine in Tomcat(6) using LDAP(Active Directory). I need to convert this to an EE (JSF2), so I am moving from Tomcat to GlassFish(v3). I have changed the web files to xhtml and configured the xml files. However, I cannot get the GlassFish LDAP configuration to authenticate. I am attaching my old web.xml and server.xml (from Tomcat) snippets and the portions of the new web.xml, sun-web.xml, and the GlassFish configuration. If anyone can help me figure out where I am missing the piece that will allow a user to be authenticated, I would appreciate it. (btw, I am not using roles, just authenticating against the LDAP db is good enought.) As it is right now, my app will prompt me to enter a user when I try to access a file in the 'protected' area and the GlassFish server throws an exception when it fails to authenticate. Because it works under Tomcat, I know I have the right information, I just don't know how to format it to get GlassFish to pass it along. Thanks. TOMCAT FILES: - Tomcat server.xml: web.xml: <web-resource-collection> <web-resource-name>Protected Area</web-resource-name> <description>Authentication Required</description> <url-pattern>/faces/protected/*</url-pattern> </web-resource-collection> <auth-constraint> <role-name>*</role-name> </auth-constraint> * BASIC Please enter your user name and password: GLASSFISH FILES: (I enabled the Security Manager on the Security panel, set the Default Realm to 'LDAPRealm', and added "-Djava.naming.referral=follow" JVM options.) - domain.xml: <auth-realm name="certificate" classname="com.sun.enterprise.security.auth.realm.certificate.CertificateRealm" /> <auth-realm classname="com.sun.enterprise.security.auth.realm.ldap.LDAPRealm" name="LdapRealm"> <property description="()" name="search-bind-password" value="xxxxxxxx" /> <property description="()" name="search-bind-dn" value="cn=xxxxxxxx,ou=Administrators,ou=Information Technology,ou=ITTS,ou=Administrative,ou=xxx,dc=xxxxxx,dc=xxx" /> <property name="jaas-context" value="ldapRealm" /> <property name="base-dn" value="ou=xxx,dc=xxxxxx,dc=xxx" /> <property name="directory" value="ldap://xxxx.xxxxxx.xxx:389" /> <property name="search-filter" value="(&amp;(objectClass=user)(sAMAccountName=%s))" /> </auth-realm> -web.xml: <security-constraint> <display-name>protected</display-name> <web-resource-collection> <web-resource-name>ProtectedArea</web-resource-name> <description/> <url-pattern>/faces/protected/*</url-pattern> </web-resource-collection> <auth-constraint> <description/> <role-name>*</role-name> </auth-constraint> </security-constraint> <security-role> <description/> <role-name>*</role-name> </security-role> <login-config> <auth-method>FORM</auth-method> <realm-name>LDAPRealm</realm-name> <form-login-config> <form-login-page>/faces/login.xhtml</form-login-page> <form-error-page>/faces/loginError.xhtml</form-error-page> </form-login-config> </login-config> sun-web.xml: Here is the exception that it throws: SEVERE: SEC1113: Exception in LdapRealm when trying to authenticate user. javax.security.auth.login.LoginException: javax.security.auth.login.LoginException: User yyyyyyy not found. at com.sun.enterprise.security.auth.realm.ldap.LDAPRealm.findAndBind(LDAPRealm.java:450)

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  • Creating a foreign key in MySQL produces error:

    - by SnOrfus
    I'm trying to create a foreign key on a table in MySQL and I'm getting a strange error that there seems to be little info about in any of my searches. I'm creating the key with this (emitted from mysql workbench 5.2): ALTER TABLE `db`.`appointment` ADD CONSTRAINT `FK_appointment_CancellationID` FOREIGN KEY (`CancellationID` ) REFERENCES `db`.`appointment_cancellation` (`ID` ) ON DELETE NO ACTION ON UPDATE NO ACTION , ADD INDEX `FK_appointment_CancellationID` (`CancellationID` ASC) ; at which point I get the error: ERROR 1452: Cannot add or update a child row: a foreign key constraint fails (alarmtekcore., CONSTRAINT FK_lead_appointment_CancellationID FOREIGN KEY (CancellationID) REFERENCES lead_appointment_cancellation (`) I've checked here but there's no data in the table.

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  • DataMapper: using auto_migrate! with many-to-many dependencies?

    - by pschuegr
    Hi, I'm trying to migrate my app from MySql to Postgresql, using Rails3-pre and the latest DataMapper. I have several models which are related through many-to-many relationships using :through = Resource, which means that DataMapper creates a join table with foreign keys for both models. I can't auto_migrate! these changes, because I keep getting this: ERROR: cannot drop table users because other objects depend on it DETAIL: constraint artist_users_owner_fk on table artist_users depends on table users constraint site_users_owner_fk on table site_users depends on table users HINT: Use DROP ... CASCADE to drop the dependent objects too. I have tried everything I can think of, and thought I had things working when I added :constraint = :skip to the field definition, but I keep getting that error back when I try and run auto_migrate. I thought that :skip meant that it would ignore the dependents, but maybe that only applies for deleting rows and not dropping tables? I should mention that I can run auto_migrate after i nuke the db once, but after that, errors. Any suggestions or advice much appreciated.

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  • Working with foreign keys - cannot insert

    - by Industrial
    Hi everyone! Doing my first tryouts with foreign keys in a mySQL database and are trying to do a insert, that fails for this reason: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails Does this mean that foreign keys restrict INSERTS as well as DELETES and/or UPDATES on each table that is enforced with foreign keys relations? Thanks! Updated description: Products ---------------------------- id | type ---------------------------- 0 | 0 1 | 3 ProductsToCategories ---------------------------- productid | categoryid ---------------------------- 0 | 0 1 | 1 Product table has following structure CREATE TABLE IF NOT EXISTS `alpha`.`products` ( `id` MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT , `type` TINYINT(2) UNSIGNED NOT NULL DEFAULT 0 , PRIMARY KEY (`id`) , CONSTRAINT `prodsku` FOREIGN KEY (`id` ) REFERENCES `alpha`.`productsToSku` (`product` ) ON DELETE CASCADE, ON UPDATE CASCADE) ENGINE = InnoDB;

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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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  • Having difficulty catching postgresql exception in sequel/ruby

    - by mhd
    I have postgresql table that has somekind of unique constraint. I have ruby script that will update this table. The ruby script should be able to switch to UPDATE instead of INSERT when this kind of error occured: PGError: ERROR: duplicate key value violates unique constraint CMIIW, sequel seems cannot catch this exception?? Anyway,sample code below is something that I would like to see to work but apparently not: @myarray.each do |x| fresh_ds = DB["INSERT INTO mytable (id, col_foo) values ('#{x}' ,'#{myhash[x]}')"] result = fresh_ds.insert catch Sequel::Error do fresh_ds = DB["UPDATE mytable set col_foo = '#{myhash[x]} where id = #{x}"] result = fresh_ds.update end end Maybe my ruby code is wrong or I missed something I don't know. Any solution? Thanks. UPDATE: code below works, the error is caught when unique constraint is violated. @myarray.each do |x| begin # INSERT CODE rescue Sequel::Error # UPDATE CODE end end

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  • Incorrect value for UNIQUE_CONSTRAINT_NAME in REFERENTIAL_CONSTRAINTS

    - by van
    I am listing all FK constraints for a given table using INFORMATION_SCHEMA set of views with the following query: SELECT X.UNIQUE_CONSTRAINT_NAME, "C".*, "X".* FROM "INFORMATION_SCHEMA"."KEY_COLUMN_USAGE" AS "C" INNER JOIN "INFORMATION_SCHEMA"."REFERENTIAL_CONSTRAINTS" AS "X" ON "C"."CONSTRAINT_NAME" = "X"."CONSTRAINT_NAME" AND "C"."TABLE_NAME" = 'MY_TABLE' AND "C"."TABLE_SCHEMA" = 'MY_SCHEMA' Everything works perfectly well, but for one particular constraint the value of UNIQUE_CONSTRAINT_NAME column is wrong, and I need it in order to find additional information from the referenced Column. Basically, for most of the rows the UNIQUE_CONSTRAINT_NAME contains the name of the unique constraint (or PK) in the referenced table, but for one particular FK it is the name of some other unique constraint. I dropped and re-created the FK - did not help. My assumption is that the meta-data is somehow screwed. Is there a way to rebuild the meta data so that the INFORMATION_SCHEMA views would actually show the correct data?

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  • Why can I create a table with PRIMARY KEY on a nullable column?

    - by AlexKuznetsov
    The following code creates a table without raising any errors: CREATE TABLE test( ID INTEGER NULL, CONSTRAINT PK_test PRIMARY KEY(ID) ) Note that I cannot insert a NULL, as expected: INSERT INTO test VALUES(1),(NULL) ERROR: null value in column "id" violates not-null constraint DETAIL: Failing row contains (null). ********** Error ********** ERROR: null value in column "id" violates not-null constraint SQL state: 23502 Detail: Failing row contains (null). Why can I create a table with a self-contradictory definition? ID column is explicitly declared as NULLable, and it is implicitly not nullable, as a part of the PRIMARY KEY. Does it make sense? Edit: would it not be better if this self-contradictory CREATE TABLE just failed right there?

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  • Django - Expression based model constraints

    - by rtmie
    Is it possible to set an expression based constraint on a django model object, e.g. If I want to impose a constraint where an owner can have only one widget of a given type that is not in an expired state, but can have as many others as long as they are expired. Obviously I can do this by overriding the save method, but I am wondering if it can be done by setting constraints, e.g. some derivative of the unique_together constraint WIDGET_STATE_CHOICES = ( ('NEW', 'NEW'), ('ACTIVE', 'ACTIVE'), ('EXPIRED', 'EXPIRED') ) class MyWidget(models.Model): owner = models.CharField(max_length=64) widget_type = models.CharField(max_length = 10) widget_state = models.CharField(max_length = 10, choices = WIDGET_STATE_CHOICES) #I'd like to be able to do something like class Meta: unique_together = (("owner","widget_type","widget_state" != 'EXPIRED')

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  • ManyToManyField error when having recursive structure. How to solve it?

    - by luc
    Hello, I have the following table in the model with a recursive structure (a page can have children pages) class DynamicPage(models.Model): name = models.CharField("Titre",max_length=200) parent = models.ForeignKey('self',null=True,blank=True) I want to create another table with manytomany relation with this one: class UserMessage(models.Model): name = models.CharField("Nom", max_length=100) page = models.ManyToManyField(DynamicPage) The generated SQL creates the following constraint: ALTER TABLE `website_dynamicpage` ADD CONSTRAINT `parent_id_refs_id_29c58e1b` FOREIGN KEY (`parent_id`) REFERENCES `website_dynamicpage` (`id`); I would like to have the ManyToMany with the page itself (the id) and not with the parent field. How to modify the model to make the constraint using the id and not the parent? Thanks in advance

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  • C# tip: do not use “is” type, if you will need cast “as” later

    - by Michael Freidgeim
    We have a debate with one of my collegues, is it agood style to check, if the object of particular style, and then cast  as this  type. The perfect answer of Jon Skeet   and answers in Cast then check or check then cast? confirmed my point.//good    var coke = cola as CocaCola;    if (coke != null)    {        // some unique coca-cola only code    }    //worse    if (cola is CocaCola)    {        var coke =  cola as CocaCola;        // some unique coca-cola only code here.    }

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  • Configuring JPA Primary key sequence generators

    - by pachunoori.vinay.kumar(at)oracle.com
    This article describes the JPA feature of generating and assigning the unique sequence numbers to JPA entity .This article provides information on jpa sequence generator annotations and its usage. UseCase Description Adding a new Employee to the organization using Employee form should assign unique employee Id. Following description provides the detailed steps to implement the generation of unique employee numbers using JPA generators feature Steps to configure JPA Generators 1.Generate Employee Entity using "Entities from Table Wizard". View image2.Create a Database Connection and select the table "Employee" for which entity will be generated and Finish the wizards with default selections. View image 3.Select the offline database sources-Schema-create a Sequence object or you can copy to offline db from online database connection. View image 4.Open the persistence.xml in application navigator and select the Entity "Employee" in structure view and select the tab "Generators" in flat editor. 5.In the Sequence Generator section,enter name of sequence "InvSeq" and select the sequence from drop down list created in step3. View image 6.Expand the Employees in structure view and select EmployeeId and select the "Primary Key Generation" tab.7.In the Generated value section,select the "Use Generated value" check box ,select the strategy as "Sequence" and select the Generator as "InvSeq" defined step 4. View image   Following annotations gets added for the JPA generator configured in JDeveloper for an entity To use a specific named sequence object (whether it is generated by schema generation or already exists in the database) you must define a sequence generator using a @SequenceGenerator annotation. Provide a unique label as the name for the sequence generator and refer the name in the @GeneratedValue annotation along with generation strategy  For  example,see the below Employee Entity sample code configured for sequence generation. EMPLOYEE_ID is the primary key and is configured for auto generation of sequence numbers. EMPLOYEE_SEQ is the sequence object exist in database.This sequence is configured for generating the sequence numbers and assign the value as primary key to Employee_id column in Employee table. @SequenceGenerator(name="InvSeq", sequenceName = "EMPLOYEE_SEQ")   @Entity public class Employee implements Serializable {    @Id    @Column(name="EMPLOYEE_ID", nullable = false)    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="InvSeq")   private Long employeeId; }   @SequenceGenerator @GeneratedValue @SequenceGenerator - will define the sequence generator based on a  database sequence object Usage: @SequenceGenerator(name="SequenceGenerator", sequenceName = "EMPLOYEE_SEQ") @GeneratedValue - Will define the generation strategy and refers the sequence generator  Usage:     @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="name of the Sequence generator defined in @SequenceGenerator")

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  • Is it possible to have multiple sets of key columns in a table?

    - by Peter Larsson
    Filtered indexes is one of my new favorite things with SQL Server 2008. I am currently working on designing a new datawarehouse. There are two restrictions doing this It has to be fed from the old legacy system with both historical data and new data It has to be fed from the new business system with new data When we incorporate the new business system, we are going to do that for one market only. It means the old legacy business system still will produce new data for other markets (together with historical data for all markets) and the new business system produce new data to that one market only. Sounds interesting this far? To accomplish this I did a thorough research about the business requirements about the business intelligence needs. Then I went on to design the sucker. How does this relate to filtered indexes you ask? I'll give one example, the Stock transaction table. Well, the key columns for the old legacy system are different from the key columns from the new business system. The old legacy system has a key of 5 columns Movement date Movement time Product code Order number Sequence number within shipment And to all thing, I found out that the Movement Time column is not really a time. It starts out like a time HH:MM:SS but seconds are added for each delivery within the shipment, so a Movement Time can look like "12:11:68". The sequence number is ordered over the distributors for shipment. As I said, it is a legacy system. The new business system has one key column, the Movement DateTime (accuracy down to 100th of nanosecond). So how to deal with this? On thing would be to have two stock transaction tables, one for legacy system and one for the new business system. But that would lead to a maintenance overhead and using partitioned views for getting data out of the warehouse. Filtered index will be of a great use here. MovementDate DATETIME2(7) MovementTime CHAR(8) NULL ProductCode VARCHAR(15) NOT NULL OrderNumber VARCHAR(30) NULL SequenceNumber INT NULL The sequence number is not even used in the new system, so I created a clustered index for a new IDENTITY column to make a new identity column which can be shared by both systems. Then I created one unique filtered index for old system like this CREATE UNIQUE NONCLUSTERED INDEX IX_Legacy (MovementDate, MovementTime, ProductCode, SequenceNumber) INCLUDE (OrderNumber, Col5, Col6, ... ) WHERE SequenceNumber IS NOT NULL And then I created a new unique filtered index for the new business system like this CREATE UNIQUE NONCLUSTERED INDEX IX_Business (MovementDate) INCLUDE (ProductCode, OrderNumber, Col12, ... ) WHERE SequenceNumber IS NULL This way I can have multiple sets of key columns on same base table which is shared by both systems.

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  • Theory Of A Weird Thought - Forms Submission

    - by user2738336
    In theory, if you were to open two computers that were perfectly synced together on a website that has a form. This form has fields where say for example the username has to be unique. Assuming both computers have the same information on the form, and in theory let's say that the submit button was pressed at the same time, and that these two computers have the exact same build and internet speed and the same response time from the server, whose information would be submitted to the database and whose information would be denied knowing the username field is unique.

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