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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5
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148 views

Which is more efficient b+ tree or search (binary or linear)?

SELECT A FROM T WHERE M > 1000 AND M < 5000; I am unable to judge which of the below is best suited for the above query: Linear search Binary search on M B+-tree with index on M B+-tree with ...
4
votes
0answers
316 views

SQL Server 2012 Error when creating Selective XML Index on XML Query Plan

I'm trying to create a database solution that will enable me to optimise high CPU/IO/Duration queries to improve overall performance of the database. Part of the optimisation requires persisting ...
3
votes
0answers
56 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) ...
3
votes
0answers
102 views

What's the point of prefixing each element in the column by its column number in multicolumn GiN indexes?

According to these slides which, I believe, are incorporated into the current implementation, each column element in multicolumn GiN indexes is prefixed by its column number and is stored separately ...
3
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0answers
35 views

Influence of index rebuild tasks in tempdb on the transaction log?

I have read pretty much about index maintenance and all the pros/cons of reorg, rebuild, online, offline, TEMPDB and timing and right now I am kind of more confused than ever before... The goal is to ...
3
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0answers
668 views

Do OR conditions in Oracle SQL queries spoil index use / cause full table scan?

I have a query on Oracle 11g of the following type, which results in a series of highly inefficient full table scans: select t.Id, t.ObjectId, t...[other Tasks columns] , od1...[ObjectData1 ...
3
votes
0answers
198 views

custom population of full text index

Is there any way to populate a full text search index without storing the backing information in the database? I don't mean using remote-blob-storage or FILESTREAM types. The backing information is a ...
3
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194 views

Key Lookup and Full-text index

I have the following query: SELECT T2.Title FROM TitleTable T1 INNER JOIN TitleTable T2 ON T2.FKID1 = T1.FKID1 WHERE T1.FKID2 = @ID_PARAM1 AND T2.FKID2 = @ID_PARAM2 AND ...
2
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0answers
69 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 ...
2
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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, ...
2
votes
0answers
33 views

B Tree and B+Tree diferencies

I'm studying B+ Tree and B Tree and I would like to understand two things about it, if someone can clarify it to me I would appreciate: Why can I store more search keys on an B+ Tree Index? My guess ...
2
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0answers
55 views

Rebuild index online without risk to other requests

We have a MS sql server 2012 enterprise database whose indices fragment very fast. We use a maintenance plan that reorganizes those indices daily, and rebuilds them weekly. The rebuild happens ...
2
votes
0answers
22 views

Combine several missing index suggestions with one index?

I investigate on missing indexes recommendations of my sql server engine. Looking at the most useful ones (for a specific table) that are candidates based on their potential usage and potential ...
2
votes
0answers
57 views

Postgres: CREATE INDEX, but very slowly, to reduce performance hit on rest of database?

I have a large production PostgreSQL (9.1) database running on Ubuntu Linux. It is currently being queried and used. However there is another use I need later, and I will need to create a large ...
2
votes
0answers
39 views

SQL Server 2012 duplicate key error with Spatial index that shouldn't be unique

We have a table that has a geometry column that is filled by a stored procedure from two x and y values whenever they're changed ( SW_GEOMETRY = GEOMETRY::STGeomFromText('POINT('+ ...
2
votes
0answers
58 views

Database fragmentation and heap SQL Server

We have critical performance issues with our production database (its around 300 gb size) We have run the following script for a few huge tables : DECLARE @db_id SMALLINT; DECLARE @object_id INT; ...
2
votes
0answers
47 views

How long does the final phase of an online index creation take?

In reading the whitepaper: Online Indexing Operations in SQL Server 2005 it says: The online index build process can be roughly divided into three phases: Preparation Build Final ...
2
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0answers
231 views

Why is this MySQL query “using where” instead of “using index”?

Could you help me with this query, please? SELECT p.patid, MAX(c1.eventdate) as eventdate from patient as p left join op_adv_effects._clinical as c1 on p.patid = c1.patid left join ...
2
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0answers
46 views

SQL Server 2005 Datawarehouse DB - Integrity failure caused by NonClustered indexes

Last year I've been working with a data warehouse database (SQL Server 2005) loaded on a daily basis during the nights. Overall database performance is acceptable. However, there is a "known error" ...
2
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0answers
87 views

Unique Index much bigger than the table itself

Pg 9.3 on debian 7. I have a very huge table in rows, about 178 million (will turn 250 million in a week and then grow 500 thousand a day), but not that huge in size, wich is 20GB, it's a small ...
2
votes
0answers
59 views

SQL Server 2008 R2 - Should I be worried at this statistics regarding indices causing locks?

We have some mild table locking issue during our peak hours so I figured the following query query taken from this site would be a good start. And boy, does it show me some seriously concerning ...
2
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0answers
58 views

ola hallengren Index Maintenance script - GUID Index

We been running ola hallengren Index Maintenance script and was ran into a problem with some indexes that have GUID as the Index Key, They are Frag and have a page count of 6,309, but they don’t get ...
2
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0answers
107 views

MySQL table partition strange behavior (slow query suddenly)

(I asked this question in "stack overflow" and was recommended to ask in here). (MySQL version: 5.6.15) I have a huge table (Table_A) with 10M rows, in entity-attribute-value model. It has a ...
2
votes
0answers
73 views

work/cache table issues, heavy inserts with heavy reads

we have a work table that stores availability of products. This table is updated with millions of inserts every night and medium amounts of inserts throughout the day. during the updates, we delete ...
2
votes
0answers
71 views

Can there be any case where it would require additional indexes while all columns compose primary key

Ok i don't know whether this question is asked before or not Here my table SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[tblProductPagesFeatures]( ...
2
votes
0answers
40 views

See indices implicitly created for foreign key constaints in MySQL

When I add a foreign key constraint to my table, SHOW INDEX doesn't show any new indices, but the overall space used by the indices in that table increases. Apparently, the index for the field I put a ...
2
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0answers
129 views

Disabled index still incurs overhead when inserting

I have a 38 million row table that I periodically truncate and refill. I disable the indexes (non-clustered) when I do this. But when I included the Execution Plan I noticed SQL Server 2005 is still ...
2
votes
0answers
480 views

PostgreSQL index array of int4range using GIN / GIST - custom operator class

Here is my table: CREATE TABLE mytable ( id INT NOT NULL PRIMARY KEY, val int4range[] ); I want to index the val column: CREATE ...
2
votes
0answers
57 views

How to make continues cluster?

I have a report table with the following index: providerid, date The table is around 30M records and it grows about 100K rows per day. I want to use in the index above as a cluster, but as I ...
2
votes
0answers
92 views

How can one improve the performance of a query that selects on a low cardinality column in MySQL?

I have a "State" column that has a low cardinality (three possible value), on which most of my queries perform an equality selection (WHERE col = 'blah') AFAIK you need something like a bitmap index ...
2
votes
0answers
343 views

Best Practice to update columnstore indexed tables

I have a table with aprox. 22 Bn rows, for each month I have made one partition that and each partition has two data files. I created the columnstore index on this table and the performance ...
2
votes
0answers
37 views

Can I read data from a 'hash field' in a legacy Ingres database?

I have been asked to read and present data from the 'hash fields' of an Ingres 2.0 database, which are apparently multiple pieces of data stored together in a single field in various combinations. I ...
2
votes
0answers
255 views

MS-SQL index not using all the available columns as seek predicates

I have a sql query on a large table (>17 million rows) that some times does not populate all the predicates before performing index seek, which results in not filtering out enough rows and slowing the ...
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 ...
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 ...
1
vote
0answers
45 views

PostgreSQL doesn't use index on inherited tables

I have two tables in PostgreSQL 9.4.5 deployed on Amazon RDS: an append only, weekly partitioned, All Positions table. These store all position readings from about 100,000 sensors. There are about ...
1
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0answers
20 views

How to bucketize using Query optimal bucketization algorithm

I am trying to implement query optimal bucketization algorithm (QOB). The input of the algorithm is D=(V,F) where V is the value of the attribute and F is the frequency of occurrence. For EXAMPLE D ...
1
vote
0answers
52 views

Which indexes should I create?

I need assistance in which indexes to create on a table, and the best approach for querying it. We use PostgreSQL. Here’s the table: create table myt ( the_time timestamp, oid int, ...
1
vote
0answers
15 views

Oracle unable to extend index but I have many space free

I have application using Oracle database, and when I'm trying to call my pl/sql function which inserts many rows in tables I get an error: unable to extend index MY_INDEX by 128 in tablespace ...
1
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0answers
51 views

SQL Server index rebuild cause database growth

I have a 80GB database with about 20GB of indices size. Whenever I build the indices online the database file will grow to gain 20GB of unallocated space, and if the unallocated space is less than ...
1
vote
0answers
24 views

Index comparison

On my Production server (SQL2008) I have a query that returns suggestions of indexes. SELECT * FROM sys.dm_db_missing_index_groups g INNER JOIN sys.dm_db_missing_index_group_stats gs on ...
1
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0answers
80 views

How can I rebuild an index on table with 100 million rows without a wait time out?

I have the following table with ~100 million rows: CREATE TABLE Result ( MetricId int NOT NULL, PeriodId int NOT NULL, Value decimal (18, 2) NOT NULL, CONSTRAINT PK_Result PRIMARY KEY ...
1
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0answers
69 views

Does “CREATE INDEX WITH DROP_EXISTING” use the bufferpool for the recreated index?

We have recreate our 4TB clustered index in ouor SQL Server. Even thought we have 1.5TB of memory we still run into the following error message: "Msg 802, Level 17, State 2, Line 30 There is ...
1
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0answers
28 views

How does PostgreSQL compute the cost for index scan?

Consider the following plan: Index Scan using foo_c1_idx1 on foo (cost=0.00..8.38 rows=1 width=37) (actual time=0.012..0.013 rows=1 loops=1) Index Cond: (c1 = 500) Buffers: shared hit=4 Total ...
1
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0answers
44 views

Can an index become inconsistent for “no reason”?

Of course, when i say no reason i mean "apparently" no reason because nothing happened on the server (forced shutdowns, data corruption, deadlocks, etc...). I ask this because, there was an ...
1
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0answers
51 views

Fragmented clustered primary key (sequential GUID) index after processing - SQL Server

I'm in the process of evaluating a schema change on the primary keys of several of our biggest tables in our software. Till now we used varchar(36) for all of our PKs and FKs and Hibernate generated ...
1
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0answers
27 views

DMV Index proposals still reported as missing

We have recently converted a big client running our patient/journal application from ORACLE to MSSQL, and after the conversion we have had quite a few performance issues. After running the DMV query: ...
1
vote
0answers
142 views

Script to find unused indexes over a period of time doesn't work in Oracle 11g

The statspack_unused_indexes.sql script described in this page would be incredibly useful to me, but it has been coded for an earlier version of Oracle. When I try to run it on 11g, I get the ...
1
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0answers
16 views

Access algorithms in Partial Index implementation of PostgreSQL 9.4?

I am studying big-O time-space complexities of different algorithms with the partial index of PostgreSQL 9.4: introsort (O(n log n)-time, O(log n)-space) and heapsort (O(n log(n))-time ...
1
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0answers
40 views

Speeding Up Query - Hangs at Sending Data - Indexed Correctly

I am looking for ways to speed up the below query. I currently have indices on FIRST, LAST, UNIT_PARENT, HomeAddressLine1, HomeAddressLine2, HomeCityNAme, HomeStateAbbreviation, HomeZipCode, HomeZip4, ...