Questions tagged [index-tuning]
The process of determining which indexes are useful and which are not.
0
votes
1answer
29 views
Efficient partition pruning with ORDER BY on same column as PARTITION BY RANGE + LIMIT?
I've set up a table in MariaDB (10.4.5, currently RC) with InnoDB using partitioning by a column of which its value is incrementing-only and new data is always inserted at the end. For this case, ...
1
vote
2answers
28 views
PostgreSQL partial index not used depending on boolean comparison
I need help understanding why a partial index would be used in one query and would not in second one which is effectively the same.
I have the following table:
Column | Type ...
0
votes
0answers
19 views
compund MongoDB index with _id
I have database with few fields:
_id, field0, field1, field2, field3, field4, field5..
I created index on as follows:
db.usertable.createIndex( { _id: 1, field1:1} )
The expected that a query ...
3
votes
0answers
26 views
Will my database index be more performant with a smaller varchar size?
We're using Mysql 5.7
We have an index over a varchar(255) column in a table of ~ 500M rows.
select distinct varchar_column from table yields seven results, with the max length 21.
A DBA consultant ...
1
vote
0answers
57 views
How does mysql optimizer works?
I have two tables t_core_blueprints,t_ci.
CREATE TABLE `t_core_blueprints` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`last_modified_on` ...
3
votes
2answers
79 views
Database design that requires an index over two tables
Using PostgreSQL (currently 9.6, but upgrades are possible), I currently have the following database layout where customers can order products, which are themselves sorted into categories (products ...
1
vote
1answer
21 views
Azure SQL Server - Cannot get rid of the sort operator
I'm using Azure SQL Server (Microsoft SQL Azure (RTM) - 12.0.2000.8 Apr 3 2019 13:27:00 Copyright (C) 2019 Microsoft Corporation), Premium tier 4 (500 DTUs).
Query: offer progress has a history ...
2
votes
3answers
139 views
Why does sql server prefer the nonclustered index over the clustered index?
I am trying to speed up a table and as I was experimenting I ran into this (what I think is) odd occurrence. I created a clustered index and a nonclustered index that should be the same thing. However,...
1
vote
0answers
23 views
Spatial index unused on nested set
I'm using the nested set architecture to store URL hierarchies in the following InnoDB table on MySQL 5.7. From my research, I've learnt that using a SPATIAL index will significantly speed up any ...
0
votes
2answers
50 views
How to index/optimize sum of two columns in PostgreSQL?
We have a database where one table contains serialized temporary data that needs to be kept for various times (usually between tens of minutes and two weeks). We also have a low priority background ...
1
vote
2answers
78 views
What is the best practice when an index with key/include columns are inversed for a second index on the same table
I have an index on a table of the form:
NONCLUSTERED INDEX [IDX1] ON [TABLE]
(
[COL_ID_A] ASC
)
INCLUDE
(
[COL_ID_B]
)
For a different query on the same table MSSMS proposes the following ...
2
votes
1answer
100 views
How to optimize the execution of query that takes too long
I am working with a query that is taking around 53 minutes to execute, which I feel is excessive.
Maria DB version: Server version: 10.1.38-MariaDB-1~stretch mariadb.org
The declaration of the ...
0
votes
1answer
61 views
Is MongoDB index creation single threaded?
I have rather big dataset - 2TB of text data, 18.000 millions of lines.
Each document is same: 5 fields: 4 strings + 1 integer.
All fields should be indexed and searched by.
That is: array of 3 ...
1
vote
0answers
41 views
Background index creation resource provisioning
I have a long running background index creation running in MongoDB. However, the CPU and RAM usage is below 30%.
Is there a way to allocate more resources to the index creation process or is it ...
0
votes
1answer
51 views
Optimizer choosing a bad index
I have a pretty simple select statement,
select column 4 from table_x where column1=:1 and column2=:2 and column3=:3
Columns 1,2 and 3 make up the primary key on the table.
For some reason, ...
1
vote
1answer
88 views
Query Index question
I am trying to figure out how I can index this query below. The table is 155 columns. It has a clustered index on the column which is not in the query. The query is dynamically created from out of the ...
2
votes
3answers
68 views
Identify proper index for group and order by date and hour (2 columns)
PostgreSQL 10.4
I have a table that has already an index on date column. Current query plan is doing a Bitmap Heap Scan using the existing date index. I would like to add a new index for this query, ...
3
votes
1answer
28 views
Is PRIMARY(ColumnA, ColumnB) + INDEX(ColumnB) + PARTITIONING(ColumnB) redundant?
I have a big table (30 millions rows) defined like this:
CREATE TABLE `drawing` (
`id` int unsigned NOT NULL,
`artist` int unsigned NOT NULL,
`imageUrl` text NOT NULL,
`uploadDate` timestamp NOT ...
1
vote
1answer
62 views
Index Optimization for Datetime comparing day of week and hour
I have a table of sensor observations with obs_ts timestamp, sensor_id text, sensor_val int, and to fill in gaps with data we have models by day of week and hour of day: model_id int, hour_of_day int, ...
3
votes
1answer
126 views
What is the best index strategy or query SELECT when performing a search/lookup BETWEEN IP address (IPv4 and IPv6) ranges?
Question: Is there a better indexing strategy or query SELECT that I can use for looking up one large data set against another large data set? Or, should I look at placing the lookup dimension table ...
5
votes
2answers
126 views
Why are partial PostgreSQL HASH indices not smaller than full indices?
I want to create the most efficient index for a sparsely populated column. I only need equality operations, so a HASH index should be beneficial.
Now I'm wondering why a partial HASH index isn't ...
3
votes
1answer
347 views
Redundant indexes in SQL Server
I am currently going through all indexes in our data warehouse as a performance tuning exercise. Several of these indexes are not used in the system stats, and I am considering removing them to reduce ...
1
vote
1answer
41 views
Advice on fine-tuning query and index for performance
Currently my query is as below:
select id_request,username_request
from darkhast_follower
where darkhast_follower.id_request != '9762952594'
AND darkhast_follower.status =0
AND NOT exists (...
-1
votes
2answers
166 views
Queries key look up [closed]
SELECT Col1, Col2, Col3, Col4, Col5, Col6, Col25...
FROM Tabl1
WHERE ( Col30 IS NOT NULL
AND Col28 <> @P0
AND DATEDIFF(
dd,
Col31,
...
1
vote
2answers
62 views
PostgreSQL: hstore trgm search on fixed key
I have a table of products with custom properties for each product. So I have props::hstore column in my table. I want the user to be able to search products by key/value by first selecting the key ...
0
votes
0answers
45 views
Slow query with order by join table
I have a SQL with multiple join left, because some data is empty.
However, I need to sort the data using a string column from a join table.
I thought about creating an index for this table, but this ...
2
votes
3answers
441 views
Struggling to create an efficient index for this query
I am struggling to create an index for a query and unfortunately I cannot change the query at all as it part of an ERP system. The problem is this query has over 1m reads and sometimes a duration of ...
7
votes
1answer
387 views
Index help for bad Query on fairly big table (2m)
I am looking for some assistance please. I have a query that is running against a fairly big table (2 million records).
I have been trying to get the indexes working efficiently. There are a few ...
0
votes
1answer
56 views
SQL Server indexes Work Sometimes [duplicate]
So I have the following indexes on my table:
CREATE NONCLUSTERED INDEX [$5] ON [dbo].[Record Link]
(
[Company] ASC,
[Record ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, ...
0
votes
1answer
19 views
Performance recommendations stuck on 'Validating'
I have been tasked with migrating a 'database from hell' to Azure SQL. It has some complicated and long-running queries (20 seconds on the S6 tier, >600 seconds on S4 tier) and I'd like to optimise ...
2
votes
2answers
155 views
Enlighten me about INCLUDE on indexes
Well, After reading Erik Darling's post Filtered Indexes: Just Add Includes I'm really curious and sad about how I use INCLUDES:
He gives some examples and etc. about INCLUDE, but I'm confused about ...
0
votes
1answer
35 views
Why are bulk multi-column key queries so slow in MySQL?
(For this question, I am using AWS/Aurora MySQL with a reasonably-spec'd RDS instance)
Consider the following schema:
Table T:
col0: the usual autoincrement primary key
col1: varchar
...
1
vote
0answers
147 views
Creating index on a big text column in postgres
We are talking about postgresql 9.5 on windows with a database which has UTF8 encoding and "English_United States.1252" (default) LC_COLLATE and LC_CTYPE.
The column is of type text and it is used ...
2
votes
1answer
145 views
PostgreSQL performance with (col = value or col is NULL)
This question deals with PostgreSQL 9.5 query performance.
The table is:
CREATE TABLE big_table
(
id integer NOT NULL,
flag bigint NOT NULL,
time timestamp with timezone NOT NULL,
val ...
-1
votes
1answer
60 views
Composite index and Normal index,redundant/duplicate index - Incurred Performance penalty [closed]
Need suggestion on below indexes, whether our composite index is enough and can the normal index be removed.
Scenario - We have ix4 and ix6 indexes as below, please review and advise if ix4 is ...
1
vote
1answer
58 views
Is there any benefit to having both an ordered and unordered index on the same column in postgres?
I have inherited a postgres database where there are two identical indexes except for their order:
CREATE INDEX avail_time_ix ON table (availability_time);
CREATE INDEX avail_time_dc_ix ON table (...
1
vote
2answers
65 views
Live update index in production database [closed]
I have read Perform Index Operations Online provided by MSFT but I couldn't find any detail information for my questions.
My questions are:
What is the impact when I update (create/drop) non-...
1
vote
1answer
75 views
Include Columns in Index : SQL Server
I have one question regarding include column in the indexes. If I have an include column which is updating its value quite often, does it update the index every time it's updating the value or does ...
1
vote
3answers
58 views
Performance tuning across two tables using indexes?
Let say I have two tables and a SQL query like this
SELECT table_a.*, table_b.*
FROM table_a, table_b
WHERE table_a.id = ?
AND table_b.col_x = table_a.col_x
AND table_b.id = table_a.id;
Would there ...
0
votes
1answer
44 views
Composite index design where only a subset will be queried
I have a table with columns A (typedate), B1 ... B24 (all boolean).
Generally, A will always be used in every query and only one of B1 ... B24. A large subset of the B columns (more than half) will ...
0
votes
0answers
31 views
Update stats as default or with a sample value
I have been reading many blogs on this and cannot come to a conclusion on update stats for VLDB;s
On SQL server 2012Sp4 and 2014Sp2 we have databases over 15 TB with 4-5 tables covering most of the ...
2
votes
1answer
52 views
Efficient predictable ordering in PostgreSQL
I have a large table of locations. I would like to efficient paginate though the table. I had previously being using an OFFSET approach however the size of the table made that approach unusable. So I ...
0
votes
1answer
66 views
use DBCC SHRINKDATABASE after rebuild / reindex [duplicate]
I have little free disk space.
Why shouldn't you use DBCC SHRINKDATABASE (DBName, TRUNCATEONLY) after every rebuild/reindex operation?
0
votes
1answer
28 views
Primary index is being used, not the one which is on the field present in the where condition
I have 2 tables, one is category table and has below coulmns and has a primary index on cat_id column.
cat_id (primary key), acc_id, islive
Another table is cat_brand table which has below fields ...
-1
votes
1answer
47 views
Adding Multiple Individual Indexes vs One Combined Index for Multiple Foreign Keys
Background
I have a "join" table that is used to join one "transactional" table with a "category" table based on multiple columns (and through several joins):
TxnTable(Entity1Name, Entity2Name, ...
2
votes
0answers
93 views
Best Way to Index Multiple Effective Date Columns
I've got a table that is primarily to represent relationships between entities (i.e. mostly composed of foreign keys). These relationships change over time, and so the table has a StartDate and an ...
1
vote
1answer
83 views
Performance Tuning ETL
I administer a datawarehouse running on SQL Server 2016. This datawarehouse has most of its ETL processing done during a nightly load, except for a few SSIS packages that run throughout the day, then ...
0
votes
1answer
29 views
I need help creating an index for timestamp
I have a query taking too long.
This is the table:
mysql> describe parking_data;
+----------------+--------------+------+-----+-------------------+----------------+
| Field | Type ...
0
votes
1answer
130 views
SQL Server 2012 Aggressive Over-Indexing when i run sp_BlitzIndex
I observed blocking and time outs in one of our production server and there is prod outage to one of the application continuously,
When i run sp_BlitzIndex i got Aggressive Over-Indexing, ran script ...
1
vote
0answers
280 views
mongodb aggregation query performance
We have a collection PurchaseOrder, it has embedded array of documents PurchaseOrderLines and another embedded document Warehouse.
The record count is about ~4m for PurchaseOrder and each purchase ...
