Questions tagged [performance]

An evaluation of whether a system works well enough to be fit for purpose. Normally performance refers to the speed with which a system completes an operation or set of operations over time.

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1answer
972 views

Select * from statement execute very slowly, innodb io read speed is low

I have a very simple query " select * from ap_statistic " running in my servers. the servers have the same hardware and software configuration (CPU 8 core, mem :32G, OS: redhat 5.5, mysql version: 5....
5
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1answer
293 views

PostgreSQL - How does multicolumn B-Tree index work with order by on 1st column and IN lookup for 2nd?

I created such table (similar to example from http://use-the-index-luke.com/sql/example-schema/postgresql/performance-testing-scalability ) CREATE TABLE scale_data ( section NUMERIC NOT NULL, ...
5
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3answers
110 views

Optimizing table/indices for getting the latest row (filtering by one additional column)

I have a SQL Server table (SQL Server 2012 SP3 Standard edition) that stores a bunch of configuration information (basically text blobs) for different organizations. The schema is something like this: ...
5
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1answer
1k views

Poor performance in my pgpool cluster

I've configured a postgres cluster with pgpool2 using the following link. The replication seems to be ok, but I ran some benchmarks (pg_bench) and the performance is lower than a single node, for ...
5
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2answers
1k views

Multi-threaded replay of master activity for load/performance testing

Does anyone know of any existing tools/products that accomplish what I'm trying to do? After searching around for a bit the only thing I could find surrounding what I'm trying to accomplish is ...
5
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1answer
3k views

SQL SERVER 2016 high CPU

I have a brand new server with SQL Server 2016. It has 24 CPU, about 80go of RAM. The thing is, sometimes, the CPU gets pretty high (> 70%) with no specific reason at all. If I look at the 'execute ...
5
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1answer
734 views

Measure Performance for INSERT, UPDATE and DELETE commands on DB2

I have a DB2 database with a table for daily transactions, which is cleared to a history table at the end of the day, every day. I insert rows to this table via java-JDBC INSERT commands and they ...
4
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2answers
563 views

Performance problem using mysql fulltext search

I have a fulltext index on a column that contains an absolute file path (file_path), for a file indexing application. There are 500 000 rows in the table. The MySQL version is 5.7.19. Most, if not ...
4
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0answers
318 views

Performance degradation after upgrade from 3.0.11 to 3.2.12

Environment: CentoOS 6 (kernel 2.6.32), MongoDB community edition 3.0.11 and 3.2.12 , storage engine MMAP, config servers on SCCC We are experiencing performance degradation when moving from 3.0.11 ...
4
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2answers
651 views

Column Cardinality and Total Number of Rows Are Equal

I have a table with 128'914'635 number of rows. Some columns cardinality (i.e. address, lastname, firstname) is equal to the total number of rows in the table (128'914'635). The queries are really ...
4
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1answer
269 views

Guidelines on best indexing strategy for varying searches on 20+ columns

I’m running a search engine for cars. It’s backed by a postgresql 9.3 installation. Now I’m unsure about the best approach/strategy on doing index optimization for the fronted search. The problem: ...
4
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1answer
89 views

Sample a Mysql table to increase performance

we are storing all our clients traffic data in a MySQL 5.1.73 database (MyISAM) and then we use it to generate user and internal statistics/graphs, always searchinng for a client id and a date/hour. ...
4
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2answers
421 views

poor and/or unreliable InnoDB performance

I recognize that there are a ton of posts like this, but after reading up on InnoDB performance problems, nothing I tried has helped. I have a database containing four InnoDB tables. The largest ...
3
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1answer
337 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), ...
3
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0answers
422 views

What can cause slow planning times for “select 1”?

I have a database that is used by a Production application. It's an db.m3.medium on Amazon RDS. We've noticed that a lot of queries are starting to get slow that typically shouldn't be slow (e.g. ...
3
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0answers
43 views

Query plan shows high negative value and the server slows down

My SQL Server 2016 had been presenting problems certain days, all process since the morning begins to run slowly than normally. Sometimes updating statistics works, sometimes not and had to reboot ...
3
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3answers
781 views

Optimise Large Record Deletion Procedure

I'm creating a database that mirrors our production database, but is lighter and anonymised - for local development purposes. Ensuring we've enough data to operate on as an engineering team, I'm ...
3
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0answers
2k views

PostgreSQL High Disk I/O

I am evaluating PostgreSQL as an alternative to Oracle. I have a database with 533 Tables which contain up to 250,000 entries. For a performance comparison, I built the datbase both on Oracle and ...
3
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1answer
651 views

AWS RDS Showing CPU spikes on a MySQL system every 5 minutes — how can I track the cause?

I'm seeing a CPU spike every 5 minutes (though it's not FIXED on the 5 minutes, every so often it's 6 minutes between a spike, then 5, 5, 5 again). None of my code runs on a 5 minute interval (it ...
3
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0answers
50 views

What is a cost of search for records in a table with an equality predicate on a non key attribute A and a static hash organization?

To speed up the search for records in a table with an equality predicate on a non key attribute A and selectivity factor fs, is preferable: A sequential organization on a key attribute ? A ...
3
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1answer
133 views

sp_primary_keys_rowset is consuming a lot of CPU

I manage a database server that supports a C#/VB.NET application and we've had a lot of CPU usage problems. I am using the following dmv query from Glenn Berry at SQLSkills: SELECT TOP(50) DB_NAME(t....
3
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0answers
146 views

Can CTE sub-statements be prevented from executing at all?

Through this strategy, time consumed by queries for my application have dropped to extreme lows; however, some queries consume more milliseconds than necessary. The reason why is that upon ...
3
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0answers
926 views

Galera cluster consume many CPU percent and CPU high load

I have implemented a cluster include three nodes: two stored nodes and one garbd (also haproxy - load balancer). Some information about servers: SSD 480G Raid1 Memory 32G Swap 16G 2xCPU, number of ...
3
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0answers
260 views

Find Most active databases that can be offloaded from a busy server

I am in the process of identifying the most active databases on the server and will be moving the databases off the current server to alleviate the load. The reason to do it is that our servers are ...
3
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0answers
226 views

Why does removing a RID by creating a clustered index lose parallelism and slow down execution by 2X

If I remove a RID lookup by replacing 2 non-clustered indices (non unique) with 2 identical clustered indicies (non-unique) where there weren't any before, why does this query slow down by a factor ...
3
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0answers
1k views

MySQL: Improve performance for one row insert into table with unique constraint

I have a table with ~ 40 mil records, with a unique index on the url column, of type varchar(255). Now the insert speed is about 30/s, is this expected? how could I improve it? I can't use bulk ...
3
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1answer
2k views

SQL Server performance issue (CXPACKET wait type)

I have a performance issue with production SQL Server 2012 which has 24 cores and 32 GB of RAM. From wait type I can see CXPACKET is on the top based on the following SQL Server metrics, should I ...
2
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0answers
27 views

Advantage of querying data outside a filtered index

Is there any way to take an advantage of having a filtered index to speed DML queries targeting data sets outside that index? My playground: Table with billion rows and 100 columns Unique clustered ...
2
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1answer
81 views

Need help in parallel execution of current running queries

I need some help in understanding if there is any problem here with very high utilization of CPU on my read-only server. Read-only means this server is secondary read-only configured via Log Shipping (...
2
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0answers
40 views

the cost decreased but the time was practically the same, why?

Table definition: CREATE TABLE schema.mylogoperation ( id_mylogoperation serial, data DATE, myschema VARCHAR(255), column_var_2 VARCHAR(255), user VARCHAR(255), action TEXT, ...
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0answers
92 views

What's the more performant database design for query speed and write overhead when storing many boolean columns?

Setting the scene I have a PostgreSQL 11 database running on a very fast 64core, 10 SSD HW RAID 10 server. In the database I need to create a table with a couple of million rows, let's call it cars. ...
2
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1answer
41 views

One vs. Many Tables for Frequently but Asynchronously Updated Columns?

As part of my Postgres 10 schema, I have two tables; current and historic -- both have the same columns. current has about 20 (+/-) columns, and holds the most up-to-date information for accounts. I ...
2
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0answers
48 views

Poor query planning in Postgres 10

The query planner in Postgres10 seems to be ignoring the fact that my tables are clustered. I have to explicitly put "hints" in my query to have it perform the correct type of join. Here's my ...
2
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0answers
41 views

How costly is changing column datatype in PostgreSQL?

I'm currently evaluating PostgreSQL for an app we are developing which comes with a weird usecase. We want to allow clients to create new fields which in turn will create new columns in a client-...
2
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1answer
50 views

Regularly updating table with huge amount of rows

I have a table containing (in addition to some metadata) a score and a boolean flag: CREATE TABLE scores ( score_id SERIAL NOT NULL CONSTRAINT score_pkey PRIMARY KEY, user_id ...
2
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1answer
78 views

Spike and time out errors every x th minute

I have very complicated situation here. Application team was reporting that they see spikes and errors every 20 mins. We checked what was running and found log backups. So we tuned log backups using ...
2
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0answers
48 views

Automating performance tests in PostgreSQL

I want to check the performance of specific queries in a Postgres database on a regular basis. Also, I want to be able to check the change in performance of different queries with any change in my ...
2
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1answer
191 views

Inefficient execution plan selected by postgresql

I have the following SQL query explain analyze select CERTIFICATE_ID, SERIAL_NUMBER, SUBJECT_DISTINGUISHED_NAME, NOT_BEFORE, NOT_AFTER, FIRST_SEEN, REVOKED, LINT_ERRORS from (...
2
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1answer
246 views

SQL Profiler plus Include Actual Execution Plan

Is there any option to show "Include Actual Execution Plan" plus query cost and recommended indexes in SQL Profiler? I see Showplan XML, but it shows only the execution plan without recommended ...
2
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1answer
34 views

How to compare across rows in large table?

I need some help with a complicated query. Here are the dataset structures I'm dealing with. This is a MySQL database. *transactions_table* zip | date ----------------- 1234 | 2010-05-01 4567 | ...
2
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0answers
137 views

What is the difference between “OPTION (OPTIMIZE FOR UNKNOWN)” and “OPTION (USE HINT('DISABLE_PARAMETER_SNIFFING'))”

Can you tell me what is difference between OPTION (USE HINT('DISABLE_PARAMETER_SNIFFING')) and OPTION (OPTIMIZE FOR UNKNOWN)?
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0answers
76 views

Is it correct to get SQL Server read write ratio from sys.dm_os_buffer_descriptors?

I'm reading a book and the author taught us a trick to calculate the read write ratio by using sys.dm_os_buffer_descriptors. I suspect the correctness of this method. After a page has been read into ...
2
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0answers
3k views

“Acknowledge over PGA limit” wait event

Is it possible for this wait event to activate/showup even when the PGA has not crossed over PGA_AGGREGATE_LIMIT? I am continuously seeing this wait event in the ASH, but the PGA allocated stays ...
2
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0answers
170 views

SQL Edition Downgrade Impact on Jobs

we’ve made a downgrade from Enterprise Evaluation Edition to Standard and we saw the over night jobs all running much longer these are ETL packages and SQL Stored Procedures to load data from ...
2
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0answers
357 views

Repair running too slow

Last week I asked a question that was answered below... I need to improve the question I asked earlier (in quotes below) and give a little more context. The answer below did help the repair ...
2
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0answers
515 views

What to do when you find slow running query?

I have two databases. One with 10.000 rows and one with 10 million rows. I have a load test and I am running it towards a rest api endpoint. This endpoint does a query to database and average ...
2
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0answers
434 views

SSIS 14 - Buffer Memory - Good practices

I've a some packages in SSIS 14 in order to extract the data from a lot of operational databases and load into my Data Warehouse. I've the following virtual machine: Windows Server R2 Standard RAM:...
2
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0answers
32 views

How much does a query of deletion costs in terms of operations when the attribute is a key or an attribute?

How much does the following query costs in terms of operations when the attribute is a key or an attribute ? DELETE FROM R WHERE ATTRIBUTE = 50 We assume we have R(K,A,B,other) a relation with ...
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0answers
556 views

Postgresql 9.6 autovacuum blocks all update operations

I have a table with following definition: CREATE TABLE public.json_stream_packet_filter ( stream_packet_id bigint NOT NULL, filter_data jsonb, CONSTRAINT json_stream_packet_filter_pkey PRIMARY ...
2
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0answers
67 views

TSQL: how to define efficient index on partitioned panel-data table?

The underlying table piddt is a panel-data structure containing three fields: (pid, dt, attribs). The defined primary key is (pid, dt). The number of rows is around 6 Billion, and the table is ...