indexing

问题 For examples: doc1: { 'name':'apple' } doc2: { 'name':'apple juice' } when I create text index with pymongo: db.products_collection.create_index([('name', TEXT)], unique=True, background=True) it give me an error: E11000 duplicate key error collection: c.items_collection index: name_text_alias_text dup key: { : "apple", : 10.5 } Some one know why? I cannot add unique=True for text string? 回答1: A text index splits strings into tokens (words), and those tokens form the keys. So in your example,

问题 Well I was developing an application usin Symfony 1.4 and Doctrine when I realized a major drawback on my Zend Lucene implementation. I have a model called Publication that is related (via foreign key relations) with a few other models (subjects, genres, languages, authors, etc.) and I'm getting they're names when adding a new document to the index (using the Jobeet tutorial way) so that I can search for publications with a given subject, genre, language, author, etc... The problem is if for

问题 I am trying to figure out "what 5-digit number when multiplied by 4 gives you its reverse?" using this code but I get error: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 5 at java.lang.String.charAt(String.java:658) at Digits.main(Digits.java:12) public class Digits{ public static void main(String[] args) { int n = 0; int b = 0; String number = Integer.toString(n); String backwards = Integer.toString(b); for (int x = 9999; x < 100000 ; x++ )

问题 This my tables: CREATE TABLE IF NOT EXISTS `test_dates` ( `date` date NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE IF NOT EXISTS `test_log` ( `id` int(10) unsigned NOT NULL, `timest` datetime NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8; ALTER TABLE `test_dates` ADD PRIMARY KEY (`date`); ALTER TABLE `test_log` ADD PRIMARY KEY (`id`), ADD KEY `emissione` (`timest`); I have this query to count logs per date: SELECT d.date, COUNT(l.id) FROM test_dates d LEFT JOIN test_log l ON l

问题 I have a working code from a tutorial but don't understand it completely. Situation: After a button was pressed in my iPhone App an AlertView appears with three buttons. Now I like to check what button the user pressed. CODE FROM THE TUTORIAL: - (IBAction)infoButtonPressed:(id)sender { UIAlertView *myAlert1 = [[UIAlertView alloc]initWithTitle:@"My Alert View 1" message:@"Here we go" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"Option1", @"Option2", nil]; [alert show]; } -

问题 I have a Postgres 9.4 database with a table like this: | id | other_id | current | dn_ids | rank | |----|----------|---------|---------------------------------------|------| | 1 | 5 | F | {123,234,345,456,111,222,333,444,555} | 1 | | 2 | 7 | F | {123,100,200,900,800,700,600,400,323} | 2 | (update) I already have a couple indexes defined. Here is the CREATE TABLE syntax: CREATE TABLE mytable ( id integer NOT NULL, other_id integer, rank integer, current boolean DEFAULT false, dn_ids integer[]

问题 I have a Postgres 9.4 database with a table like this: | id | other_id | current | dn_ids | rank | |----|----------|---------|---------------------------------------|------| | 1 | 5 | F | {123,234,345,456,111,222,333,444,555} | 1 | | 2 | 7 | F | {123,100,200,900,800,700,600,400,323} | 2 | (update) I already have a couple indexes defined. Here is the CREATE TABLE syntax: CREATE TABLE mytable ( id integer NOT NULL, other_id integer, rank integer, current boolean DEFAULT false, dn_ids integer[]

问题 How do you specify the Fill Factor when creating an index in MySql? 回答1: You don't. http://dev.mysql.com/doc/refman/5.0/en/create-index.html However, it is an 'accepted' feature request for version 6.x: http://bugs.mysql.com/bug.php?id=18178 So, don't hold your breath on seeing it any time soon. 回答2: Assuming that you are using InnoDB, it seems like this is only supported at database level, not index level. The setting is called innodb_fill_factor and defaults to 100 see https://dev.mysql.com

问题 I have a query where I am searching against a string: SELECT county FROM city WHERE UPPER(name) = 'SAN FRANCISCO'; Now, this works fine, but it doesn't scale well, and I need to optimize it. I have found an option along the lines of creating a generated view, or something like that, but I was hoping for a simpler solution using an index. We are using DB2, and I really want to use an expression in an index, but this option seems to only be available on z/OS, however we are running Linux. I

问题 In Microsoft SQL Server and MySQL, index names need to unique within the table, but not within the database. This doesn't seem to be the case for PostgreSQL. Here's what I'm doing: I made a copy of a table using CREATE TABLE new_table AS SELECT * FROM old_table etc and need to re-create the indexes. Running a query like CREATE INDEX idx_column_name ON new_table USING GIST(column_name) causes ERROR: relation "idx_column_name" already exists What's going on here? 回答1: Indexes and tables (and