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Questions tagged [performance-tuning]

Improving the performance characteristics of a database application or system.

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28 views

Need Help in extended events SQL Server

I have created an extended event as below. I want to know how to query the historical data using T-SQL to see the issues at particular timestamps. The trace is running as of now CREATE EVENT SESSION [...
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0answers
78 views

How to investigate locks impact on MSSQL performance? [closed]

I have performance issues with 3rd-party application on MSSQL database. By query sys.dm_os_wait_stats (from sqlskills) I have this results: WaitType Wait_S Resource_S Signal_S ...
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1answer
25 views

does sequence of columns in where condition matters the sequence of composite key? in Oracle Database

here, In the code where exists clause contains all primary key columns in where, I want to know that the sequence of this columns in it, matters in query performance. update temp_fd_dtl_svj a set ...
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1answer
22 views

Filegroup: [primary] dbcc shrinkfile() need balanced extent counts per file when done

I'm working with a ~1 terabyte db, server 40+cores, memory 500G+, db files on SAN (no control over lun segments), the bottleneck now is file contention. Currently running 2014 but by final "release" ...
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0answers
4 views

Performance considerations for a standalone server running Postgres 9.4 on 8 CPU core with 47GB RAM

I'm running: Postgres 9.4 8 CPU cores 47GB RAM shared_buffers = 13.8GB work_mem = 32MB The server gets its workload from 6 web application nodes which connect using JDBC connection pooling. Each web ...
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1answer
70 views

Partitioning and Performance of DB Table [closed]

After partitioning a table the performance of select queries returning large datasets degrades as compared to performance earlier. For small datasets there is no degradation. No change in index is ...
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2answers
41 views

What kind of SSD to speed up querying a lot of data?

For research purposes I am using a big MariaDB database (~500 GB) with 20 Tables (engine: myISAM) and around 9 Billion rows. Due to missing free storage on my Laptop (16 GB RAM), I put the data on an ...
3
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1answer
80 views

Empty Table: Insert into Table WITH (TABLOCK)

We have a clustered index table which is empty. Table has around eg: 20 columns, 50 million rows, around (40GB). Is it best practice to apply Insert With (TABLOCK) for empty tables such as this? The ...
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1answer
38 views

Are these stats reasonable? If not, where should I start?

The below is the output result of mysqladmin for our mysql server which has been having consistent problems for months since we switched from a dedicated server to the cloud. In the switch, we ...
-1
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0answers
52 views

Slowly Changing Dimension table Index Optimization

What is the optimal way to created index on slowly changing dimension tables which have Begin and EndDates? If I want to select when Customer owned house or enrolled in school. Should EndDate be in ...
2
votes
3answers
145 views

SQL Server: Performance Insert Into vs Select Into

I am hearing different things from colleagues/research. What are good guidelines in performance for, Select Into vs Insert into when creating a temp table? I know difference is minimal for small ...
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0answers
15 views

any knowledge or experience with dynamic ax [duplicate]

I support a system called "dynamics ax" and sometimes my optimizer picks a good plan, drops it and then picks a bad plan (where the same code is been ran). users who usually wait for 10 seconds start ...
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0answers
41 views

oracle slow query with diferent user

I have a question with an oracle query that takes almost 20 minutes when it is executed from a schema and yet when it runs as sys users it runs in 1 second maximum ... how is this possible? ... I do ...
1
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1answer
30 views

Debug Connection Pool Error

I have been getting the below error. System.Data.Entity.Core.EntityException: The underlying provider failed on Open. ---> System.InvalidOperationException: Timeout expired. The timeout ...
4
votes
1answer
107 views

why is this left join faster than an inner join?

So I'm tuning this query, and I am pretty sure that in this instance, I can replace an inner join with a left join without affecting the data. However, I'm not entirely sure why this is faster. Here ...
1
vote
1answer
52 views

When to Disable and Recreate Indexes in Data Warehouse ETL?

We are moving data from Staging Database into Kimball Data Warehouse DB. I am hearing different ideas regarding when to disable and rebuild indexes. Stage tables are truncated every day for each new ...
2
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0answers
52 views

Recommendations around managing large amounts of data that needs to be aggregated (SUM)

I am looking for alternatives to redesign a part of our system that needs to perform cumulative SUMs over large data sets of rows based on user and dates. How the system works We are running a web (...
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1answer
85 views

Index vs Statistics [duplicate]

In SQL Server, when to create statistics only on a table column instead of index and when create to index (which creates statistics as well automatically)? I mean both improve query performance then ...
2
votes
2answers
88 views

Slow query that includes a WHERE clause with SUBSTRING

I have the following query in SQL Server 2016, as there is no code for the "enter code here" column, I had to do a search with SUBSTRING. But as expected it is slow, the query ends in 00:03:37. with ...
4
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2answers
69 views

CXPACKET wait on SQL Server

Recently I am experiencing performance issue on a SQL Server database and I have two queries that show me the wait as shown below, one of the databases on this server is a member of Always On replica, ...
1
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0answers
60 views

pgbench - 20-30% variation in benchmark results (non-repeatable benchmarks)

Problem I'm trying to use pgbench to help me tune Postgres for my hardware, but I'm seeing a very strange behaviour. I cannot seem to get a stable number for TPS in consecutive runs of pgbench. Since ...
0
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0answers
33 views

RAC DB Slowness - AWR Report

While going through the AWR report found that the row lock waits on indexes and buffer busy waits are more (rest of the stats look normal). Could someone tell me if we can interpret by the below if ...
0
votes
1answer
86 views

sp_WhoIsActive waiting resource

I have a huge query in SQL Server 2016 – when I run the query for a subset of records, it completes in 15 minutes. When I extrapolate it to total number of records, it is supposed to be complete in 1 ...
0
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1answer
109 views

TSQL or SSIS for Direct Insert Speed Performance

I am moving data from Table A into Table B. Tables have the exact same DDL, table structure, and are straight inserts. We are Not transforming or modifying data. If TSQL Server and SSIS have the ...
3
votes
1answer
91 views

Identify Query Waiting on resources

I have some query with CXCONSUMER wait time when i ran sp_whoisactive as shown in the screenshot below. When i checked the status it is suspended.That means it is waiting for some process to release ...
2
votes
1answer
119 views

Microsoft Optimal method for columns into 1 word: XML Raw or Concat

What is fastest, performance method to make columns into one word? Does Microsoft have recommendation, or is there performance Big-O studies on FOR XML RAW vs Concat? Company has multiple tables with ...
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2answers
135 views

Is NEWSEQUENTIALID unique within a database for Many tables?

Is NEWSEQUENTIALID unique within a database? We plan many tables in a database with NEWSEQUENTIALID, inserting simultaneously and want to ensure every guid will be unique, regardless if they are in ...
0
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1answer
61 views

powerful VPS but slow MS SQL- why? [closed]

VPS (Contabo) : 10 cores (Xeon E5 2.2GHz), 60 GB RAM, SSD, MS SQL Web Edition (configured to use 10 CPUs), Windows Server 2016 When running SQL takes ~32GB of RAM, When I execute SQL a stored ...
0
votes
1answer
75 views

Update sys.job$ set this_date=:1 where job=:2 as one of the most time-consuming queries - oracle

I am currently helping some organization with their Oracle database performance. They are using Oracle 11gR2 Standard Edition in Windows 2008. As there are no enterprise performance packages ...
0
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1answer
38 views

Oracle 9i historical long queries since instance startup

please I would like to know any query that shows the queries or the top 10 queries that take more time to finish since the beginning of the instance with user and the sql sentence, I have seen several ...
0
votes
3answers
225 views

Create Slowly Changing Dimension table from Repeated Data

I am receiving transaction snapshot data from a file, it contains a history of repeated data. Currently trying to find Slowly Changing Dimensions on table with [ProductId] Business Key. Many ...
0
votes
1answer
61 views

Loading 400 Million Records into MySQL Hangs on “Sending Data”

I have a large dataset of approximately 420 million records and I was able to load them into a temporary table in a timely manner of about 15 minutes using a LOAD DATA INFILE statement. Super awesome. ...
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2answers
23 views

MariaDB “EXECUTE AS” or User Impersonation

With MariaDB, is there a way to impersonate a user execution context when connected with a higher privileged account? For instance, when connected with a "MasterUser" execute a SELECT using the more ...
7
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2answers
274 views

SQL Staging Tables: Primary Key Clustered or Heap

We are taking legacy flat txt files and inserting them into stage tables with SSIS.The question arose whether table should have primary clustered key index or not. This is direct flat file import with ...
1
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1answer
92 views

SSIS Data Source: Embedded Queries, Stored Procedures, or Functions

We are moving data from OLTP server into Data Warehouse server, utilizing SSIS to conduct this. When writing queries from the OLTP Data Source, it it better to utilize? 1) Inline Embedded queries 2)...
0
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2answers
34 views

Index columns on pre-production?

If I understand correctly, indexing a column will increase SELECT speed but decrease INSERT speed. Say your app is new and you have identified columns which are good candidates for indexing (based on ...
0
votes
1answer
36 views

Query Locks Table And Takes Long Time to Run

I have a query that can take a long time to run. I tried running the same query in a test server and it runs very quick. However, in production it seems to hang and causes blocking of other queries. ...
1
vote
1answer
38 views

SQL Except Statement and Add in One more column

How do I conduct a Except statement and Add in one more column? Three tables with the exact same structure. (CustomerTransaction1,CustomerTransaction2, CustomerTransactionDiff) I want the LoadDate ...
3
votes
1answer
224 views

Memory Pressure in SQL Server - Enable LPIM or not?

I have slow query execution in my SQL Server 2016. Server configurations: Total Physical Memory : 128 GB SQL server Max Memory : 102 GB Transaction replication is enabled. Database Size:1.6 TB ...
0
votes
1answer
73 views

SP_WhoIsActive - RESOURCE_SEMAPHORE_QUERY_COMPILE

Had an issue with one of our production servers earlier today. Many transactions were suspended with RESOURCE_SEMAPHORE_QUERY_COMPILE wait. Have sp_whoisactive data logged to table every minute. Below ...
8
votes
1answer
188 views

What is the algorithm behind the EXCEPT operator?

What is the internal algorithm of how the Except operator works under the covers in SQL Server? Does it internally take a hash of each row and compare? David Lozinksi ran a study, SQL: Fastest way to ...
0
votes
1answer
24 views

DB2 Workfile scan

We just migrate from LUW to zos and we're finding that in z/os the accesspath explains show new node named WFSCAN (Workfile scan) and this rises when there is a join, group by or any kind of sort. ...
0
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2answers
1k views

SSIS vs T-SQL Join Performance, Difference Databases on Same server

We are researching the performance difference between SSIS Lookup and T-SQL Join. We want to join two tables; tables are in the same SQL server instance, different databases. I suspect for small ...
2
votes
1answer
328 views

Oracle 12c - Slow query to tables ALL_CONS_COLUMNS and ALL_CONSTRAINTS

We have successfully upgraded Oracle 11g to Oracle 12c. So far it's been going well. But We noticed one problem, queries made for Oracle's constraint tables (ALL_CONS_COLUMNS and ALL_CONSTRAINTS) are ...
1
vote
1answer
170 views

How Large Table before Using Clustered Columnstore Index

At what size should we consider applying Columnstore Index on a table? Is there a SQL Server storage or design guidance? Our Data Warehouse is 5TB total. Additionally, we have tables which are 100GB ...
1
vote
2answers
324 views

Can a table have Both a Clustered Columnstore Index and Nonclustered Columnstore Index?

Can I a table have both Clustered Columnstore Index and Nonclustered Columnstore Index? I am seeing example strategies to use Clustered Columnstore Indexes with only Nonclustered Binary row indexes. ...
3
votes
1answer
149 views

MySQL creates tables very slow

On my home machine running Ubuntu 18.04 and MySQL version 8.0.12 with better hardware, table creation, database creation and so on are very slow. On my other computer with older hardware (slower SSD), ...
1
vote
1answer
113 views

what are memory fractions and how to get rid of them (or the sort operator) in the example below?

This execution plan has the following memory fractions: Memory fraction input:1, Memory Fraction Output:1. it is a very simple query: SELECT [a].[activityId], ...
2
votes
2answers
572 views

Performance differences between RID Lookup vs Key Lookup?

Are there any performance differences between when a non-clustered index uses the clustered index's key to locate the row vs when that table doesn't have a clustered index and the non-clustered index ...
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votes
1answer
123 views

What is the Optimized Way to Dynamic SQL Select all Columns from Table?

I just generated this script. It will select all columns from a table dynamically. Is there an alternative or more clean, efficient way of conducting this? Additionally, I want to place line breaks ...