index

Why/when/how is whole clustered index scan chosen rather than full table scan?

IMO, please correct me... the leaf of clustered index contains the real table row, so full clustered index, with intermediate leaves, contain much more data than the full table(?) Why/when/how is ever whole clustered index scan chosen over the full table scan? How is clustered index on CUSTOMER_ID column used in SELECT query which ...

iphone tableview index config

Hi all, I have a tableview with 2 sections. - (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView { NSArray *listArray = [@"Save|Hist"componentsSeparatedByString:@"|"]; return listArray; } The index that I would prefer is these 2 sections to be located in the center of the index instead of one at the top and...

Why my mysql doesn't use index?

I'm tuning my query for mysql. the schema has index of user_id (following..) but the index is not used. why? Env: MySQL4.0.27,MyISAM SQL is the following : SELECT type,SUM(value_a) A, SUM(value_b) B, SUM(value_c) C FROM big_record_table WHERE user_id='<user_id>' GROUP BY type Explain: |table |type |possible_keys |key |key_len...

Index performance with WHERE clause in SQL

I'm reading about indexes in my database book and I was wondering if I was correct in my assumption that a WHERE clause with a non-constant expression in it will not use the index. So if i have SELECT * FROM statuses WHERE app_user_id % 10 = 0; This would not use an index created on app_user_id. But SELECT * FROM statuses WHERE app_...

Constraint is key is index is constraint?

in SQL Server Management Studio (SSMS) 2008 R2 Dev on the table (because I cannot ask without it) --SET ANSI_NULL_DFLT_ON ON create table B (Id int) I create unique constraint ALTER TABLE B ADD CONSTRAINT IX_B UNIQUE (ID) WITH (IGNORE_DUP_KEY = ON) SSMS shows that I do not have any constraint but have a key + index instead w...

MySQL index selection criteria

Hi there, I have a scenario, where I have though optimized the query, but don't understand on what basis the query optimizer choses to use a particular index. I am running the following query. SELECT r.review_id FROM game_reviews r INNER JOIN game_subchannel gs ON r.game_id = gs.game_id WHERE gs.subchannel_id=4 My table...

phpMyAdmin wants to add multiple indices as one multi-column index

Hey, I'm creating tables using phpMyAdmin and want to define two different columns as indices. I'm not trying to create a multi-column index but phpMyAdmin creates them as such. Are there any possible issues with that? The fields don't relate to each other directly and both fields will not be used in WHERE clauses simultaneously. Consi...

Can I access the index from within a foreach?

In PHP I can do this: $list = array("element1", "element2"); foreach ($list as $index => $value) { // do stuff } In C# i can write: var list = new List<string>(){ "element1", "element2" }; foreach (var value in list) { // do stuff () } But how can I access the index-value in the C# version? ...

how to get index keys from mysql index?

i have an innodb mysql table with a varchar(100) field called 'word'. i created a btree index on an that field. if i do a query like select * from table where word = 'non-linear', i get all variations of that word. so results would include (Non-linear, Non-Linear, non-Linear, etc...). it seems to me that that index doesnt care about ...

jQuery selector: defining array index

hi, i'm having several tables in my html markup which dont have any attributes and i'm wondering: is it possible to define a jquery selector which directly picks eg. the 3rd table? thx ...

C negative array index

this is my struct : struct Node { struct Node* data; struct Node* links[4]; } assuming there is no padding, does Node->links[-1] guaranteed to be pointing on Node::data ? ...

Very slow bitmap heap scan in Postgres

I have the following simple table that contains traffic measurement data: CREATE TABLE "TrafficData" ( "RoadID" character varying NOT NULL, "DateID" numeric NOT NULL, "ExactDateTime" timestamp NOT NULL, "CarsSpeed" numeric NOT NULL, "CarsCount" numeric NOT NULL ) CREATE INDEX "RoadDate_Idx" ON "TrafficData" USING btree ("RoadI...

Change schema in Solr without reindex

First of all, sorry about my english: In Solr, if we have a field in the schema with stored="true" and we change the analyzer associated with that field, are any posibility of update just this field without reindex all the documents ? Using the "stored" values of the field with the new analyzer without any datasource or external data. ...

noindex no follow variable- have I done this correct?

I have this script in the head of all my pages- which in an include: <?php if (isset($robots) && $robots == "off") { $robots = '<meta name="robots" content="noindex,nofollow">'; print $robots."\n"; } else { $robots = '<meta name="robots" content="index,follow">'; print $robots."\n"; } ?> After the hea...

Choosing optimal indexes for a SQL Server table

I have a SQL Server table with the following structure: CREATE TABLE [dbo].[Log]( [LogID] [bigint] IDENTITY(1,1) NOT NULL, [A] [int] NOT NULL, [B] [int] NOT NULL, [C] [int] NOT NULL, [D] [int] NOT NULL, [E] [int] NOT NULL, [Flag1] [bit] NOT NULL, [Flag2] [bit] NOT NULL, [Flag3] [bit] NOT NULL, [Counter] [int] NOT NULL, [Start...