A database structure that can improve the speed of queries at the cost of disk space and slower inserts/updates. It stores a copy of one or more columns but structures the data differently to allow for faster access.

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4
votes
1answer
730 views

Should one always VACUUM ANALYZE before REINDEXing in PostgreSQL 8.4?

Early in the morning every day a pgAgent job refreshes the contents of table A from table B on my PostgreSQL 8.4 database. Table A contains around 140k records across 91 columns and has two indexes - ...
1
vote
1answer
4 views

How to estimate PostgreSQL reindexing time?

How do you estimate the total time reindexing an entire table will take in PostgreSQL? I have a large PostgreSQL database, the primary table of which has 15 million records and 100 columns, and 200 ...
2
votes
2answers
250 views

MS SQL Included Columns in an Index: is there something like “too many”?

We have a table in one of our databases with approximately following structure: Field1 int primary key Field2 int foreign key A Field3 int foreign key B Field4 int foreign key C Field5 ... Field70 ...
0
votes
1answer
20 views

Splitting the table to get more clusterization options - will it help? [on hold]

Complete theory. Let's assume we have a table with a few millions rows. The table has clustered index over PK, and it is important for quick fetching of particular rows. However, the table also has a ...
3
votes
0answers
60 views

Sort operation sql server 2012

I am trying to optimize a query and the sort operation(91% cost) is the costliest operation.Any help will be appreciated. Query is : SELECT TOP 1 ArchiveType ,CONVERT(NVARCHAR(30), A.StartTime, 20) ...
36
votes
4answers
27k views

Index Seek vs Index Scan

Looking at an execution plan of a slow running query and I noticed that some of the nodes are index seek and some of them are index scan. What is the difference between and index seek and an index ...
0
votes
1answer
23 views

Full text indexes on big tables

I have a news website where I store my articles in a table that looks like that: Id title data Where data contains the content of the article and is the biggest column in the database by far. ...
7
votes
6answers
877 views

Fast reads without paying the price on writes

We have a large append-only table containing financial transactions. On average 1000 transactions are inserted per minute. Since there are now more and more usecases where we actually want to read, ...
0
votes
1answer
24 views

How to create unique index for both cases

I have table in PostgreSQL with sender_id and receiver_id and a unique index: add_index :my_table, [:sender_id, :recipient_id], unique: true Table will created, if sender_id: 1, and recipient_id: ...
3
votes
1answer
29 views

What indexing to be used over string columns(text type) with string length around 3000 characters

I am using open source columnar dbms (postgresql+Cstore). I am trying to speed up the response time of queries. My database has tables with strings mostly. String columns contain huge data (up to ...
3
votes
1answer
42 views

Fill Factor: Will the fill factor change automatically after it detects the changes in the index pages?

So lets say that the default fill factor is left at 0 initially. Data has been loaded up into the server and one fine weekend, the index rebuild job is run. Now if it detects any new data which must ...
8
votes
1answer
8k views

MySQL INNODB corruption after server crash during concurrent truncate command

My server crashed today I think due to a concurrent truncate table command on one of our INNODB tables. The server could be restarted, but after it starts up, everytime I try to issue an SQL command, ...
2
votes
1answer
58 views

Can I use an index to optimize select clause, versus where clause?

I'm not sure if this question has been answered, because I'm not sure of the proper wording to describe what I need. So here it is: I am trying to optimize a database that is running very slowly, ...
5
votes
1answer
3k views

How to create an index on an integer json property in postgres

I can't figure out for the life of me how to create an index on a property of my json column which is an integer. I tried it this way (and also dozens of others) CREATE INDEX user_reputation_idx ON ...
2
votes
2answers
48 views

Is there any point with a combined index on all columns in a table?

I have stumbled upon several cases of indices set on all columns of a table. In my mind this will be as efficient as the full table scan that would occur without the index. Is this correct or is there ...
1
vote
1answer
126 views

MYSQL - FORCE INDEX ON A DELETE

UPDATE backup.records FORCE INDEX(IDX_records_deviceId) SET readyToBeDeleted = 1 WHERE deviceId = 226219 AND timestamp <= 1445255546 *** (1) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space ...
2
votes
2answers
2k views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...
2
votes
0answers
70 views

How to estimate reindexing time?

How do you estimate the total time reindexing an entire table will take in PostgreSQL? I have a large PostgreSQL database, the primary table of which has 15 million rows with 100 columns and 200 ...
0
votes
1answer
47 views

Creating index using dynamic SQL [closed]

I have following code for creating gist index CREATE INDEX web_stats_project_107_properties_crosspromo_gist_idx ON web_stats_project_107 USING gist (properties) WHERE properties @> ...
10
votes
2answers
345 views

Minimizing Indexed Reads with Complex Criteria

I'm optimizing a Firebird 2.5 database of work tickets. They're stored in a table declared as such: CREATE TABLE TICKETS ( TICKET_ID id PRIMARY KEY, JOB_ID id, ACTION_ID id, STATUS str256 ...
8
votes
2answers
408 views

Unused Indexes Best Practices

Based on this query, if I see a low amount of total reads (very close to 0 or 0, like 1 or 2) and a high or moderate amount of user updates (I couldn't find inserts or deletes with this query) with a ...
0
votes
1answer
56 views

Oracle over-indexed tables

I am trying to improve performance of a view in Oracle 11g, the view joins 11 tables, the 3 biggest tables in the query are 40, 27, 19 milions of rows. I found that each of these big tables has more ...
2
votes
3answers
80 views

MySQL query takes over a minute to complete

I am trying to pull calls associated with website visits from our huge database... I have got SQL that works, pulls correct results it just takes over minute to complete... Here is the SQL SELECT ...
0
votes
0answers
24 views

Why is my spatial index not being used on Mariadb?

I have a spatial index on geo column, but when I do EXPLAIN it doesn't show that the index is being used. Can anyone tell why? EXPLAIN SELECT AsText(geo) FROM marker WHERE ...
3
votes
1answer
7k views

Why does MySQL (InnoDB) table get faster after OPTIMIZE TABLE, but then don't work?

I have a Django web application that stores data in a MySQL InnoDB database. There is a particular page that is accessed a lot on the django admin, and the query is taking a long time (~20 seconds). ...
2
votes
1answer
43 views

How to create an index to be picked by query

I have created multiple indexes one after another, but my query doesn't want to pick them :( CREATE INDEX x ON gan.paid (project_id, country_iso_code, source, date(created_at)); CREATE INDEX x ...
2
votes
4answers
115 views

Copy indexes from one table to another

I have a series of ETL jobs in which I create a swap table using CREATE TABLE table1_swap LIKE table1. In order to make the populating of table1_swap faster I do not include the indexes. When I'm ...
0
votes
1answer
58 views

Oracle index usage

I came across V$SEGMENT_STATISTICS dynamic view. What statistic should I consider to tell if index block is being updated from time to time (on the contrary to scenario where index block is created ...
9
votes
1answer
125 views

Why can my index seek estimate the right number of rows and the sort operator can't?

I've a query that uses a function on the predicate, something like this: commentType = 'EL' AND commentDateTime >= DATEADD(month,datediff(month,0,getdate()) - 13,0) I have a filtered index on ...
0
votes
0answers
35 views

Is there an equivalent of virtual columns in mysql?

Currently I'm taking a look at amazon's new aurora database and I'd like to check how my current setup performs there. The original table is on maria DB and contains a virtual column ...
9
votes
5answers
268 views

Getting a scan though I expect a seek

I need to optimize a SELECT statement but SQL Server always does an index scan instead of a seek. This is the query which, of course, is in a stored procedure: CREATE PROCEDURE dbo.something ...
1
vote
0answers
52 views

Query with join to a table on a different database need an index

I'm creating a query that one of its joins is made to a table from a different database. The query analyzer is suggesting the creation of an index, however I don't have permission to add objects to ...
4
votes
2answers
698 views

Check if an index exists by comparing columns

We are currently using ALL_IND_COLUMNS to check if an index exists by its name or the columns it is using. The problem is that we can only check if the index exists with columns in a specific order. ...
2
votes
0answers
29 views

MySQL Performance issue: ~360ms to fetch 120 rows with 10 columns

I have the following tables: CREATE TABLE `events` ( `id` int(11) NOT NULL AUTO_INCREMENT, `status` varchar(255) COLLATE utf8_unicode_ci DEFAULT 'draft', `publish_at` datetime DEFAULT NULL, ...
1
vote
0answers
26 views

Mysql slow copying to tmp table to indexing

I try to indexing table. The table size is about 60GB. But indexing query is hang on 'copying to tmp table' 18 hours. I found advice setting 'myisam_sort_buffer_size' myisam_sort_buffer_size : 128M ...
0
votes
2answers
116 views

List full text indexes in Oracle database

Using SQL Server, it's possible to execute a query that returns all the columns that contain a full text index. How can I do something similar using Oracle? Is it possible?
3
votes
4answers
367 views

Is there any scenario where the existence of one or more Indexes in a table can prejudice it?

The title sums it up. I've learned and always heard that indexes in tables improve CRUD operations. A developer that I met last weekend told me that he does not like Indexes because they are bad - ...
4
votes
3answers
11k views

Listing indexes and constraints

I am looking at a SQL Server database for an application I have inherited. I have not looked into SQL Server for approximately 10 years, so please bear with me. The database table I am looking at has ...
1
vote
1answer
196 views

Sybase ASA: Saving and dropping all foreign keys and most Primary Keys for (Bulk) Insert

Background Information: I am trying to migrate from an ASA 12 Database, to a ASA 12 Database by using a Remote Server. I have to migrate a lot of Rows (not all), spread over a lot of tables (not ...
0
votes
1answer
39 views

sqlite database table with 1000's of columns

I am using sqlite3 in an application to conduct an alalysis of distances between sets of points. Distances between these points have been precomputed using dijkstra's algorithim and left me with a ...
34
votes
2answers
22k views

Create index if it does not exist

I am working on a function that allows me to add an index if it does not exist. I am running into the problem that I cannot get a list of indexes to compare to. Any thoughts? This is a similar issue ...
1
vote
1answer
50 views

Slow query performance on large table with no unique keys

I have a table that has approximately 20 million records and I'm having a very hard time improving the performance of the following query. It's taking well over a minute to run. SELECT ...
4
votes
2answers
122 views

Will the Query Optimizer Ignore A Fragmented Index?

Scenario: I have a heavy OLTP table with an index. I see many inserts, updates and deletes and the index fragments heavily within a day or less. While on day one of the index build, the optimizer ...
0
votes
1answer
58 views

Innodb full table Scan

mytable is an InnoDB table with (a, b) as the primary key. Does this query check all table? Select * from mytable where ( b='2' and c='3') I want to find out if 'cluster' structure ...
1
vote
1answer
921 views

Slow insert with MySQL full-text index

I use a full-text index in a MySQL table, and each insert into this table takes about 3 seconds. It seems that MySQL rebuilds (a part) of the full text index after each insert/update. Is this right? ...
1
vote
1answer
167 views

Index to fix this query MySQL

We have an extremely large forum running lots of third party software (Most of which doesn't run all that well) and we're starting to optimize things as time allows. This query keeps popping up in the ...
1
vote
3answers
230 views

mysql need help optimizing query

I have a table containing servers logs, and another table containing rules to match certain and drop them. The logs tables contains around 1 million rows, and there are about 20-30 rules. The ...
1
vote
1answer
30 views

Why is MySQL choosing that index?

I have a large indexed table with over 35 million rows. Here are the indexes, with a naming convention that shows their sequential column order: IDX_E93438363DAE128B, ...
6
votes
1answer
143 views

Why is my SP_HELPINDEX showing a lot of indexes?

Using sp_helpindex My_table I have this list: But my table has only these indexes: Why is this happening? I'm using a query to search for "equal indexes" in a particular table. This query is ...
0
votes
1answer
179 views

Use index intersection feature in mongo 2.6 to compound shard key

I am having three indexes like name,age,salary. I can use them as compound index as per 2.6 (name and age together). But can i use the same indexes as compound shard key like name and age. i also have ...