Search results “Oracle cardinality cost”
What is Cardinality and High Cardinality and Low Cardinality in Oracle
What is Cardinality and High Cardinality and Low Cardinality in Oracle SQL Tutorial SQL Tutorial for beginners PLSQL Tutorial PLSQL Tutorial for beginners PL/SQL Tutorial PL SQL Tutorial PL SQL Tutorial for beginners PL/SQL Tutorial for beginners Oracle SQL Tutorial
Views: 676 TechLake
Oracle tutorial : Using execution plan to optimize query in oracle
Oracle tutorial: Explain plan for query optimization in Oracle PLSQL oracle tutorial for beginners using execution plan to optimize query sql query analyzer sql query cost analysis https://techquerypond.wordpress.com This oracle tutorial show you how to use EXPLAIN PLAN in oracle. This video covers how to check cost of the query from DBMS_XPLAN.DISPLAY . You can find the cost of the query using the Using EXPLAIN PLAN FOR and based on the result you can optimize the query for faster performance. Subscribe on youtube: https://www.youtube.com/channel/UCpiyAesWNYOXSz5GPq8lbkA For more tutorial please visit #techquerypond https://twitter.com/techquerypond
Views: 8923 Tech Query Pond
Oracle SQL Tuning - How to Read Execution Plans (Explain Plan)
In this free tutorial you will learn how to generate and read (interpret) an execution plan in Oracle Databases. See more FREE Oracle Tuning tutorials at http://skillbuilders.com/free-oracle-tutorials. Understanding what the Oracle Database does with your SQL is essential to tuning - and the execution plan is the key. Oracle Certified Master DBA John Watson will provide a brief introduction (4 minutes) - which includes John's tuning methodology, then demonstrate EXPLAIN PLAN, SQL*Plus AUTOTRACE and DBMS_XPLAN.DISPLAY_CURSOR. In the tutorial, John will teach you: - How to read an execution plan - Find the 1st step in the plan - Decipher the order of the steps in the plan - That EXPLAIN PLAN can be very misleading Prerequisites: To get the most from this tutorial, you should: 1 Know how to code SQL 2 Be familiar with SQL*Plus 3 Know - in very general terms - what an execution plan is. 4 Have a basic understanding of the Library Cache (this is where Oracle Database stores parsed SQL statements) 5 Have a basic understanding of the Cost Based Optimizer (this is the part of the database that parses your SQL, creates an execution plan. Hopefully the correct - most efficient - plan).
Views: 62514 SkillBuilders
Oracle Performance Tuning - Read and interpret Explain Plan
Connect with me or follow me at https://www.linkedin.com/in/durga0gadiraju https://www.facebook.com/itversity https://github.com/dgadiraju https://www.youtube.com/c/TechnologyMentor https://twitter.com/itversity
Views: 36544 itversity
Oracle Cost Based Optimizer Basics
When it comes to writing efficient queries there are a few key concepts that need to be understood. One of them is the Oracle Cost-Based Optimizer (CBO). Although it's called a cost-based optimizer it's actually not the cost we need to focus on primarily to understand why the optimizer makes certain decisions. In this webinar, you will learn the basics of the CBO, see why it is crucial that the optimizer's picture of the data fits reality, why cardinality and selectivity estimates matter so muc
Views: 58117 Redgate Videos
Oracle Optimizer Cost Calculation from explain plan
This presentation describes the method to understand how oracle calculate cost during explain plan generation
Views: 678 debasis maity
Oracle SQL Tuning Re-Optimizing Execution Plans with Cardinality Feedback
Cardinality feedback, introduced with Oracle Database 11g, has been significantly enhanced with 12c. Cardinality feedback allows the CBO to learn from a cardinality estimate mistake and re-optimize the execution plan. Learn more in this free SQL Tuning tutorial. See all free Oracle Database tutorials at http://www.skillbuilders.com/free-oracle-tutorials.
Views: 3008 SkillBuilders
Why Won't Oracle Use My Index - 12c Attribute Clustering - Lesson 1
Sometimes a poor clustering factor is the cause when Oracle Database cost based optimizer does not choose to use an index. With Oracle 12c ( EE) offers a new feature that can really help - "Atrribute Clustering". This is implemented with a new keyword on CREATE TABLE - "CLUSTERING BY LINEAR ORDER". In this Free Tutorial from SkillBuilders and Oracle Certified Master DBA John Watson, you'll get a brief refresher on clustering factor and a demonstration of CREATE TABLE - "CLUSTERING BY LINEAR ORDER" - so the CBO will use your index! In this first lesson, John will provide a brief review of clustering factor. See all 6 lessons - FREE - at http://www.skillbuilders.com/12c-attribute-clustering
Views: 357 SkillBuilders
SQL Server Cardinality Estimation – Quick Notes – Part 1
In this video you will learn how the SQL Optimizer uses Density information to compute default cardinality estimations Twitter: http://www.twitter.com/SQLMaestros Twitter: http://www.twitter.com/A_Bansal http://www.SQLMaestros.com http://www.amitbansal.net
Views: 2768 SQLMaestros
07 07 Index Selectivity
Views: 329 oracle ocm
Using Auto DOP, Part 1
This video is the first in a two-part presentation on how to use the Auto DOP feature of Oracle Database 11g, Release 2. Copyright © 2012 Oracle and/or its affiliates. Oracle® is a registered trademark of Oracle and/or its affiliates. All rights reserved. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the "Materials"). The Materials are provided "as is" without any warranty of any kind, either express or implied, including without limitation warranties of merchantability, fitness for a particular purpose, and non-infringement.
15a  Index Selectivity
Views: 75 B's March
14  Index Cardinality
Views: 45 B's March
SQL Tuning How to Tune Joins - Lesson 1
How do you tune SQL Joins? Start with the most important ingredient - the join order! In this free tutorial by Oracle Certified Master DBA John Watson of SkillBuilders.com you will learn what is the best join order and how to get the optimal join order. Watch all Lessons, FREE, at http://skillbuilders.com/tuning-joins-optimal-join-order.
Views: 3320 SkillBuilders
Oracle SQL Tuning - Equal SQL is not Always Equal
Learn how and why equivalent SQL statements can have a dramatic effect on performance. Certified Master J Watson demonstrates...See all our free Oracle Database tutorials at http://skillbuilders.com/free-oracle-tutorials. The Oracle Database cost-based optimizer (CBO) should recognize equivalent SQL statements and re-write them into the most efficient form. Well, nothing is perfect - not even Oracle Database. Sometimes the way you write your SQL can have a dramatic effect on performance. Presented by John Watson, Oracle Certified Master DBA. Some experience with SQL tuning is expected.
Views: 1870 SkillBuilders
Oracle Database SQL Tuning with Constraints - Lesson 1 of 5
Learn how to tune SQL - especially in Data Warehouse environments - with Constraints. Constraints provide critical information to the Cost Based Optimizer in the Oracle Database. Don't drop your constraints for query performance! In these 5 lessons, Oracle Certified Master DBA John Watson will demonstrate how constraints - unique, foreign key, not null - improve the execution plan and thus performance of SQL in an Oracle database. View all 5 lessons, free at http://www.skillbuilders.com/oracle-database-sql-tuning-with-constraints.
Views: 892 SkillBuilders
The Evils of Implicit Conversions and other SQL Skullduggery
Presented by Tom Kyte Thurs 21st June 2012 Summary SQL and PL/SQL are deceptively simple, user-friendly languages, which is great for productivity, but also makes it relatively easy to write bad, non-scalable code. Certain features, in particular, seem to sound an irresistible siren call into a world of Oracle applications that perform poorly and yield unpredictable results. In this webinar, Tom Kyte, a Senior Technical Architect at Oracle Corporation, and the man behind asktom.oracle.com, takes a look at a few of the worst offenders: Triggers - much trickery is possible via triggers, and much of it causes pain, confusion and unexpected side effects Indexes, NULLs and cardinality - misinformation abounds with regard to the effect of NULLs on cardinality estimates, and the impact of NULLs on index use Implicit conversions - strings to numbers, strings to dates, raw to string... probably #2 on the list of 'bugs I see time and time (and time) again' With Tom's typically example-driven approach, you'll see first-hand evidence of the damage caused when fundamental features are misused, misunderstood and implemented badly. A live Q+A session with Tom follows the presentation. For our complete archive, and to sign up for upcoming webinars please go to http://www.red-gate.com/oracle-webinars
Views: 587 Redgate Videos
How to Think Like the SQL Server Engine, Part 3: Statistics and Memory Grants
Why does one query get wildly different execution plans? Learn how statistics influence your query plans, discover how to see your own statistics, and understand how stats help build memory grants.
Views: 4544 Brent Ozar Unlimited
Query Tuning 101 What to Look for in Autotrace Output
You're up and running with autotrace, looking at the actual execution plan for a query. Now the real work begins! What is it you're actually looking for in the execution plan? This video shows what you need to investigate and how to use the HotSpot feature of SQL Developer 4.1 to highlight parts of the query you need to pay attention to. ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 7659 The Magic of SQL
Oracle SQL Developer - Comparing SQL Execution Plans
This is a short video about a feature in SQL Developer which alllow any DBA or developer to compare different execution plans of a SQL Statement. My Blog: https://navneetupnejadba.wordpress.com/ Slideshare: https://www.slideshare.net/navneetupneja1/sql-developer-powerful-free-tool-for-developers-and-dbas
Views: 94 Navneet Upneja
Statistics histogram Cardinality In simple word.
The SQL Server query optimizer uses distribution statistics when creating a query plan. The statistics provide information about the distribution of column values across participating rows, helping the optimizer better estimate the number of rows, or cardinality, of the query results. Cardinality (SQL statements) In SQL (Structured Query Language), the term cardinality refers to the uniqueness of data values contained in a particular column (attribute) of a database table. The lower the cardinality, the more duplicated elements in a column
Views: 284 SqlIsEasy
SQL Tuning for Beginners Lesson 1 When and Why to Tune SQL
Lesson 1 in this tuning tutorial Oracle Certified Master DBA John Watson discusses when a SQL should be tuned and why. i.e. Don't waste your time tuning things that will not help.
Views: 726 SkillBuilders
Reading Oracle SQL Execution Plans - Practice Makes Perfect
To tune a SQL statement, you need to understand the execution plan. Can you identify the 1st step in an execution plan? The 2nd? The 3rd? In this short tutorial, Oracle Certified Master DBA John Watson of SkillBuilders uses a MERGE JOIN to help you understand how to find the order of execution, essential for SQL tuning.
Views: 1115 SkillBuilders
Oracle Database SQL Tuning with Direct and Indirect Reads
Oracle Database SQL Tuning tutorial. Learn what direct and indirect reads are and what impact they have on tuning SQL in Oracle Database. In this free tutorial from www.SkillBuilders.com, Oracle Master DBA John Watson will explain and demonstrate what direct / indirect reads are, pros and cons, why they can cause instability in the performance of your SQL (unpredictable response time), why stored outlines, SQL plan baselines and hints usually don't help. Perhaps most importantly, John will tell you what you can do about it. Intended Audience: Experience Oracle DBA's, developers and anyone with Oracle SQL tuning experience.
Views: 1620 SkillBuilders
A Cost Based Optimizer
50% Performance Tuning Course: https://www.udemy.com/sql-server-performance-tuning-101/?couponCode=Website
Views: 365 Mike
Oracle SQL Performance Tuning for Developers: Understand Explain Plans
Understanding Explain Plans is an excerpt from Oracle SQL Performance Tuning for Developers: http://www.informit.com/store/oracle-sql-performance-tuning-for-developers-livelessons-9780134117027 6+ Hours of Video Instruction The focus of Oracle SQL Performance Tuning for Developers LiveLessons is to illustrate coding techniques that ensure a consistent response time between instances and releases of the Oracle database. This course works closely with performance tuning of actual SQL statements. Description In this video training, Dan Hotka starts out with a complete overview of the Oracle architecture so students can get an understanding how their SQL and applications can take advantage of the computing environment. This course then goes in-depth on understanding and controlling the Explain Plan, which is how and in what order Oracle retrieves data. The discussion includes considerable detail, with SQL examples, on how the optimizers--both rule-based and cost-based, but mostly cost-based--make their decisions. Students will work with a variety of SQL statements, reviewing Explain Plans and making changes to make these SQL statements perform better. Lectures include index design, using hints and coding style to control the Explain Plans, and how to use useful tools such as index monitoring, SQL Trace, and the PL/SQL profiler. This LiveLessons course takes a close look at indexes: how Oracle selects them, why they are sometimes not used, and how to tell if indexes are being used. This course includes Oracle10g, Oracle11g, and Oracle12c SQL tuning topics. Skill Level Intermediate Learn How To Read and understand Explain Plan content Review an Explain Plan and tell quickly if this is a good plan Understand a good index column candidate from a not-so-good candidate Quickly tell the likelihood if your SQL will use an existing index Use coding and a variety of Hints (directives) that can produce better performing SQL Execute and interpret SQL trace output Who Should Take This Course Oracle programmers Oracle database administrators who need additional training on SQL tuning Course Requirements Working knowledge of the SQL query language http://www.informit.com/store/oracle-sql-performance-tuning-for-developers-livelessons-9780134117027
Views: 3176 LiveLessons
Oracle Database 12c Security - Oracle Virtual Private Database (VPD)
Learn how to use Oracle Virtual Private Database (VPD) to secure your data. See all lessons at http://skillbuilders.com/12c-TSDP-Tutorial First, Virtual Private Database. What is it? Answer: It's a declarative technique for enforcing security. Typically, it's based on user application context. That was the first limitation of 8i. Backed with 8i context were session-specific. The context variables were sort in the PGA. That means you simply couldn't use this in a web environment. However, global context, with use of 9i, Virtual Private Database became usable for web applications with connection pooling. But whether you're using it to client server or on a three tier environment, it's declarative technique rather than a programmatic technique. I can go behind the back of the application as a DBA and generate predicates to get appended to all SQLs. Select, insert, update, delete the end users. Issue the SQL and I will generate a predicate that filters the access. It's impossible to bypass. All users will have predicates appended to all their code. It doesn't matter whether they're using SQL Plus, Discoverer, Business Objects, Crystal Reports, eBusiness Suites, whatever they're using, I as DBA can filter their access to roles. The end result, different users see different data sets while running the same code and accessing the same tables, hence, the name Virtual Private Database. Different users will think they're seeing a totally different set of tables, but in fact it's one column database, one set of tables hosting a single application shared by all the users. The mechanism - you can apply VPD to tables, to views, to synonyms, and a declarative technique. Once the technique you write a function that generates the predicate, you associate the function with the table. From then on whenever the user issue SQL against that table the Cost-Based Optimizer rewrites the code. The Cost-Based Optimizer rewrites the user SQL to call the function to generate the predicate. The predicate is then appended to the SQL and it's the modified SQL that is parsed and executed. Let's see how this actually works. I'm working here by the way. This is just a perfectly normal 12.1 database. But what I'm going to demonstrate at this point will in fact work on 11g as well. I'm not going to be using any of the 12c enhancements to VPD for this little demonstration. I'll work in the scott schema. What do we have to do? We write a function to generate the predicate string. Create function. And I'll my function vpdf. The function must conform to a fixed specification. It must take two varchar arguments. One of the arguments is intended to be the schema to which the function will be applied. The other argument is the object within the schema to which the function will be applied. And it must return a varchar2, which is the generated predicate. Let's begin. Within this function you can do just about anything. There are some limitations. It's impossible for the function to query or update the table against which the VPD calls here is going to be applied or we violate the rules of purity that we come across so often with PL/SQL. But apart from that, it can do just about anything - including a number of dreadful side effects can be introduced by writing VPD functions. I'm going to do a very simple one on this one. I'll shall simple return immediately a predicate. What predicate? Ename, which is the ename column from this scott.emp table. Ename should equal sys_context. I'll go to the local context, my user end context, and just extract session user. We can see that John has tested this earlier today and therefore the object already was suggesting and he's just dropping it now and cleaning up the recreate. I hope you realize these really are live demonstrations. I'm not just running scripts. I've created a function. What's that function going to do? It's going to return this value here. Test it. Always test it and see what it's actually going to do. I'll select vpdf. I have to give it a couple of arguments. This one will do for now.
Views: 4371 SkillBuilders
Why Did Your SQL Execution Plan Change? | Alfredo Krieg
Oracle ACE Alfredo Krieg offers advice on tools for improving database performance in this 2 Minute Tech Tip recorded at the 2016 Great Lakes Oracle Conference in Cleveland, OH.
SQL Tuning with Oracle Database 12c Histograms
Learn the new 12c options for creating histograms. See all free video tutorials at http://www.skillbuilders.com/free-oracle-tutorials. In this free tutorial, Oracle Certified Master DBA John Watson demonstrates what histograms do (provide correct cardinality), the difference between histogram types (Frequency and Height Balanced). You will also learn the importance of the auto sample size algorithm in 12c and the new "Hybrid" and "Top Frequency" type histograms.
Views: 3418 SkillBuilders
Analysing Parallel Execution Skew - DFOs and DFO Trees
This is the second part of the video tutorial "Analysing Parallel Execution Skew". In this part I cover the concepts of Data Flow Operations (DFOs) and Data Flow Operation Trees (DFO Trees). Getting a grip at these concepts is important for understanding some of the effects that will be demonstrated in the later parts of this video tutorial. This tutorial also covers new parallel 12c features. See the initial part here: https://www.youtube.com/watch?v=4YKDns1EyTw If you're interested in reproducing the SQLs analysed here, you can find the scripts as part of the following blog post: http://oracle-randolf.blogspot.de/2014/04/analysing-parallel-execution-skew-data.html
Views: 938 Randolf Geist
otw14 christian antognini
Views: 1248 kyle Hailey
Oracle Database 11g: SQL Tuning Workshop
'עמי אהרונוביץ, מנהל תחום אורקל בג'ון ברייס מכללת הי-טק, יו"ר ארגון משתמשי אורקל בישראל. מייסד ומנכ"ל DBACES , מציג את הקורס לשיפור ביצועים בסיבת אורקל - SQL TUNING למפתחים ולמנהלי בסיס נתונים. לפרטים נוספים על הקורס הקליקו כאן:http://bit.ly/17kSIYj בואו להיות חברים שלנו בפיסבוק : http://on.fb.me/J6Ru6b
Views: 230 JohnBryceTraining
Histograms Pre-12c and now
Anju Garg is an Oracle Ace Associate with over 12 years of experience in IT Industry in various roles. Since 2010, she has been involved in teaching and has trained more than a hundred DBAs from across the world in various core DBA technologies like RAC, Data guard, Performance Tuning, SQL statement tuning, Database Administration etc. She is a regular speaker at Sangam and OTNYathra.  She also writes articles for All Things Oracle. She is passionate about learning and has keen interest in RAC and Performance Tuning. She shares her knowledge via her technical blog at http://oracleinaction.com/ ABSTRACT--- To improve optimizer estimates in case of skewed data distribution , histograms can be created. Prior to 12c frequency and height balanced histograms could be created.  if no. of buckets >= NDV, frequency histogram is created and the optimizer makes correct estimates. If no. of buckets < NDV, height balanced histogram is created and accuracy of optimizer estimates depends on whether a key value is an endpoint or not. The problem of optimizer misestimates in case of height balanced histograms is resolved to a large extent in Oracle Database 12c by introducing top-frequency and hybrid histograms which are created if no. of buckets < NDV. This webinar explores Pre as well post 12c histograms while highlighting the top-frequency and hybrid histograms introduced in Oracle Database 12c.
31.  SOQL Performance Series Part 3  - Selectivity
In this episode we will look at what makes a query selective and how query thresholds are generated.
Views: 890 cloudbites tv
Oracle Tuning Tutorial - Long Full Table Scans Part 5 of 5
See all 5 tutorials, free, at SkillBuilders.com/OracleTuningFullTableScans. In summary, serial full table scans were always indirect before 11.2, parallel scans always direct before 11.2. These are the two critical parameters. That hidden parameter _serial_direct_read, remember, defaults to auto so your application may start behaving very differently as you upgrade from 11.2.01 or 11.2.02. Parallel_degree_policy, that defaults to manual. But again, it becomes an option when you go to 11.2 to enable the automatic facility which allows not only automatic tuning to the degree of parallelism but also enables the ability to make indirect reads when doing a full table scan.
Views: 1563 SkillBuilders
SQL Tuning How to Tune Joins - Lesson 2 of 4 - Optimal Join Order
Tune your SQL joins! Learn what "filtered rows percentage" is and how to get the optimal join order. A free tutorial from SkillBuilders and Oracle Certified Master DBA John Watson. See all lessons, Free, at http://skillbuilders.com/tuning-joins-optimal-join-order.
Views: 1499 SkillBuilders
SQL Tuning for Beginners 2 How SQL Executes
Learn Oracle SQL Tuning. In this lesson (#2) OCM John Watson teaches the SQL Execution Cycle. See all FREE lessons at http://www.skillbuilders.com/sql-tuning-for-beginners-free-tutorial.
Views: 502 SkillBuilders
Oaktable World 2014 Jonathan Lewis on Calculating Selectivity
Oaktable World 2014 Jonathan Lewis on Calculating Selectivity
Views: 1025 kyle Hailey
"Why We Built Our Own Distributed Column Store" by Sam Stokes
How do you understand the behaviour of complex distributed systems in production? Distributed systems can fail in unpredictable, hard-to-detect ways. To track down problems quickly, you need to look for patterns and correlations in your data, trying different ways of breaking it down. "Does the problem occur on just one host, or one partition, or for particular customers?" Sub-second complex queries over large data volumes in real time: sounds like a tall order. The Scuba paper from Facebook describes an architecture that can do it: a low-latency, distributed, schemaless database. Scuba achieves fast queries by storing all data in memory. It stores the raw events, and fans out queries to multiple nodes, so it can support complex queries including aggregates (like mean and percentile statistics) and breakdowns by fields of arbitrary cardinality. Building Honeycomb, we needed a database with these properties, but we had additional constraints: multi-tenancy, cost to serve, and the limited resources of a startup. This talk describes Retriever, a custom-built database inspired by Scuba. Retriever ingests events from Kafka, and chooses disk over memory, using an efficient column-oriented storage model. I'll discuss interesting aspects of the implementation, and lessons learned from operating a hand-rolled database at production scale with paying customers. Sam Stokes HONEYCOMB Sam Stokes is a software engineer who can't leave well enough alone. He's compelled to fix broken things, whether they are software systems, engineering processes or cultures. After watching too many systems catch fire, he's building better smoke detectors at Honeycomb; in a past life he cofounded Rapportive and built recommendation systems at LinkedIn.
Views: 4870 Strange Loop
AIOUG - North India Chapter  Webinar - Adaptive Query Optimization in 12c
About Speaker Anju Garg is an Oracle Ace Associate with over 12 years of experience in IT Industry in various roles. Since 2010, she has been involved in teaching and has trained more than 100 DBAs from across the world in various core DBA technologies like RAC, Data guard, Performance Tuning, SQL statement tuning, Database Administration etc. SSince 2010, she has been involved in teaching and  has  trained more than 100 DBA's from across the world in various core DBA technologies like RAC, Data guard, Performance Tuning, SQL statement tuning, Database Administration etc. She is  certified for - Oracle 12c OCP (DBA) - Oracle 11g R2 RAC OCE - Oracle 11g Performance Tuning OCE - Oracle 11g SQL statement Tuning OCE - Oracle 11g OCP (DBA) - Oracle 9i OCP (DBA) She presented papers on following papers during SANGAM 14 - Histograms Pre-12c and now - Adaptive Query Optimization Her white paper on " Histograms Pre-12c and now" was published in Issue7 of ORACLE CONNECT  (AIOUG publication)  published in Dec 2014. She is passionate about learning and has keen interest in RAC and Performance Tuning. She shares her knowledge via her  technical blog at   http://oracleinaction.com/ .
Cost Based Optimizer Framework for Spark SQL: Spark Summit East talk by Ron Hu/Zhenhua Wang
In Spark SQL’s Catalyst optimizer, many rule based optimization techniques have been implemented, but the optimizer itself can still be improved. For example, without detailed column statistics information on data distribution, it is difficult to accurately estimate the filter factor, cardinality, and thus output size of a database operator. With the inaccurate and/or misleading statistics, it often leads the optimizer to choose suboptimal query execution plans. We added a Cost-Based Optimizer framework to Spark SQL engine. In our framework, we use Analyze Table SQL statement to collect the detailed column statistics and save them into Spark’s catalog. For the relevant columns, we collect number of distinct values, number of NULL values, maximum/minimum value, average/maximal column length, etc. Also, we save the data distribution of columns in either equal-width or equal-height histograms in order to deal with data skew effectively. Furthermore, with the number of distinct values and number of records of a table, we can determine how unique a column is although Spark SQL does not support primary key. This helps determine, for example, the output size of join operation and multi-column group-by operation. In our framework, we compute the cardinality and output size of each database operator. With reliable statistics and derived cardinalities, we are able to make good decisions in these areas: selecting the correct build side of a hash-join operation, choosing the right join type (broadcast hash-join versus shuffled hash-join), adjusting multi-way join order, etc. In this talk, we will show Spark SQL’s new Cost-Based Optimizer framework and its performance impact on TPC-DS benchmark queries.
Views: 875 Spark Summit
Cost Based Optimizer in Apache Spark 2 2 continues -  Zhenhua Wang &  Wenchen Fan
Apache Spark 2.2 ships with a state-of-art cost-based optimization framework that collects and leverages a variety of per-column data statistics (e.g., cardinality, number of distinct values, NULL values, max/min, avg/max length, etc.) to improve the quality of query execution plans. Leveraging these reliable statistics helps Spark to make better decisions in picking the most optimal query plan. Examples of these optimizations include selecting the correct build side in a hash-join, choosing the right join type (broadcast hash-join vs. shuffled hash-join) or adjusting a multi-way join order, among others. In this talk, we'll take a deep dive into Spark's cost based optimizer and discuss how we collect/store these statistics, the query optimizations it enables, and its performance impact on TPC-DS benchmark queries. Talk contributors: Zhenhua Wang (Huawei Technologies) and Wenchen Fan (Databricks) Session hashtag: #SFdd2
Views: 684 Databricks
Ask TOM Office Hours: Prepare Optimizer for Proof of Concept or Benchmark
Held on May 1 2018 If you are running an Oracle Database proof of concept or benchmark focusing on performance, what optimizer settings should you use? What statistics do you need to gather and how should you gather them? In this session Nigel Bayliss shows how you can get consistent results and avoid burning time chasing problems. Covers Oracle Database 12c Release 1 onwards. 3:55 The Adaptive Optimizer (12.1) 8:44 The Mechanics of Adaption 12:03 Adaptive Optimizer Settings 16:18 Recommended Defaults 18:53 12.1 Proof of Concept Recommendations 21:26 12.2+ Proof of Concept Recommendations 34:35 Regathering Statistics 42:24 Dynamic Sampling and Parallel 44:55 More General Recommendations AskTOM Office Hours offers free, monthly training and tips on how to make the most of Oracle Database, from Oracle product managers, developers and evangelists. https://asktom.oracle.com/ https://developer.oracle.com/ https://cloud.oracle.com/en_US/tryit music: bensound.com
Views: 180 Oracle Developers
Partner Webcast – Managing Exadata with Oracle Enterprise Manager 12c - 25 Sep 2014
Oracle Enterprise Manager 12c is system management software that delivers centralized monitoring, administration, and life cycle management functionality for the complete Oracle IT infrastructure, including engineering systems. With a broad set of end-to-end monitoring, administration, configuration management, provisioning, and security capabilities, Enterprise Manager Cloud Control reduces the cost and complexity of managing computing environments. Oracle EM12c is using a holistic approach to manage Oracle Exadata Database Machine allowing administrators to monitor and manage Exadata hardware and software from single console. Presenter: Alexey Kotelnitzky – EM Specialist, FORS Distribution | FORS Group Oracle Partner Hub Migration Center Russia (http://blogs.oracle.com/imc) [Read More @ https://blogs.oracle.com/imc/entry/managing_exadata_with_em_12c]
Views: 1279 Oracle IMC
Viewing executions plans in Oracle database - Hebrew presentation by Eran Koren
In this hebrew presentation I show some of the ways to view execution plans of SQL statements in Oracle: * Autotrace in SQL*Plus * DBMS_XPLAN procedures * DBMS_WORKLOAD_REPOSITORY (AWR SQL Report) * GUI tools Enjoy, Eran Koren [email protected] צפייה בתכניות פעולה באורקל - ערן קורן
Views: 219 Eran Koren
Oracle 10g, 11g, 12c Expert Performance Tuning C & As 2 of 3
In this tutorial you will learn how to do performance tuning on Oracle 10g, 11g, 12c databases.
Views: 2434 DBA Pro

Typo in college admissions essay question
Cover letter for foreman position
Legal investigator cover letter
Lanxess newsletter formats
Olow emu plains newsletter formats