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  • why does mysql have so many more open and fragmented tables than tables in the DB?

    - by kswift
    I've been working making our database run a little smoother and had good results over the past week. But there are still some things I dont understand. For one thing, the database has 25 tables. But mysql status shows 512 are open: mysqladmin status Uptime: 212854 Threads: 1 Questions: 43041 Slow queries: 7 Opens: 2605 Flush tables: 1 Open tables: 512 Queries per second avg: 0.202 I've read that isam opens extra file descriptors and a few other reasons why the number of open tables might be higher than 25, but I am guessing that 512 is not a good thing. Any suggestions on why this might be or what I should be looking into? I've also been using mysqltuner and its been helpful. But it has consistently listed the number of fragmented tables at 207. In phpmyadmin I've selected all the tables and optimized them several times. It hasn't reduced the number of fragmented tables that mysqltuner reports. I think I am missing some important concept about how this all works. Does anyone have any suggestions to point me in the right direction or narrow down google searches or just generally help me be less clueless? Thanks!

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  • Mysqld increases the load on the CPU and drops after flush-tables

    - by mirage
    Help please advice on the issue. Normal load on the cpu 20-30% us + sy. After restoring the database files from the slave server (same version) began a periodic problem. mysql starts to load the cpu at 100% (us + sy grows proportionally). The queue is growing, everything slows down. But with mysqladmin flush-tables are normalized for a few hours. Dedicated linux server running mysql 2 x E5506 24Gb RAM, database size 50Gb. [OK] Currently running supported MySQL version 5.0.51a-24 + lenny4-log [OK] Operating on 64-bit architecture -------- Storage Engine Statistics --------------------------------------- ---- [-] Status: + Archive-BDB-Federated + InnoDB-ISAM-NDBCluster [-] Data in MyISAM tables: 33G (Tables: 1474) [-] Data in InnoDB tables: 1G (Tables: 4) [-] Data in MEMORY tables: 120K (Tables: 3) [-] Reads / Writes: 91% / 9% [-] Total buffers: 12.8M per thread and 7.1G global [OK] Maximum possible memory usage: 15.8G (66% of installed RAM) 4000 - 5500 rps key_buffer = 1536M max_allowed_packet = 2M table_cache = 4096 sort_buffer_size = 409584 read_buffer_size = 128K read_rnd_buffer_size = 8M myisam_sort_buffer_size = 64M thread_cache_size = 500 query_cache_size = 100M thread_concurrency = 24 max_connections = 700 tmp_table_size = 4096M join_buffer_size = 4M max_heap_table_size = 4096M query_cache_limit = 1M low_priority_updates = 1 concurrent_insert = 2 wait_timeout = 30 server-id = 1 log_bin = /var/log/mysql/mysql-bin.log expire_logs_days = 10 max_binlog_size = 100M innodb_buffer_pool_size = 1536M innodb_log_buffer_size = 4M innodb_flush_log_at_trx_commit = 2 How to solve the problem?

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  • MySQL Tables Missing/Corrupt After Recreation

    - by Synetech inc.
    Hi, Yesterday I dumped my MySQL databases to an SQL file and renamed the ibdata1 file. I then recreated it and imported the SQL file and moved the new ibdata1 file to my MySQL data directory, deleting the old one. I’ve done it before without issue, however this time something is not right. When I examine the (personal, not MySQL config) databases, they are all there, but they are empty… sort of. The data directory still has the .ibd files with the correct content in them and I can view the table list in the databases, but not the tables themselves. (I have file-per-table enabled, and am using InnoDB as default for everything.) For example with the urls database and its urls table, I can successfully open mysql.exe or phpMyAdmin and use urls;. I can even show tables; to see the expected table, but then when I try to describe urls; or select * from urls;, it complains that the table does not exist (even though it just listed it). (The MySQL Administrator lists the databases, but does not even list the tables, it indicates that the dbs are completely empty.) The problem now is that I have already deleted the SQL file (and cannot recover it even after scouring my hard-drive). So I am trying to figure out a way to repair these databases/tables. I can’t use the table repair function since it complains that the table does not exist, and I can’t dump them because again, it complains that the tables don’t exist. Like I’ve said, the data itself is still present in the .ibd files and the table names are present. I just need a way to get MySQL to recognize that the tables exist in the databases (I can find the column names of the tables in question in the ibdata1 file using a hex-editor). Any idea how I can repair this type of corruption? I don’t mind rolling up my sleeves, digging in, and taking a bunch of steps to fix it. Thanks a lot.

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  • SQL SERVER – Identify Numbers of Non Clustered Index on Tables for Entire Database

    - by pinaldave
    Here is the script which will give you numbers of non clustered indexes on any table in entire database. SELECT COUNT(i.TYPE) NoOfIndex, [schema_name] = s.name, table_name = o.name FROM sys.indexes i INNER JOIN sys.objects o ON i.[object_id] = o.[object_id] INNER JOIN sys.schemas s ON o.[schema_id] = s.[schema_id] WHERE o.TYPE IN ('U') AND i.TYPE = 2 GROUP BY s.name, o.name ORDER BY schema_name, table_name Here is the small story behind why this script was needed. I recently went to meet my friend in his office and he introduced me to his colleague in office as someone who is an expert in SQL Server Indexing. I politely said I am yet learning about Indexing and have a long way to go. My friend’s colleague right away said – he had a suggestion for me with related to Index. According to him he was looking for a script which will count all the non clustered on all the tables in the database and he was not able to find that on SQLAuthority.com. I was a bit surprised as I really do not remember all the details about what I have written so far. I quickly pull up my phone and tried to look for the script on my custom search engine and he was correct. I never wrote a script which will count all the non clustered indexes on tables in the whole database. Excessive indexing is not recommended in general. If you have too many indexes it will definitely negatively affect your performance. The above query will quickly give you details of numbers of indexes on tables on your entire database. You can quickly glance and use the numbers as reference. Please note that the number of the index is not a indication of bad indexes. There is a lot of wisdom I can write here but that is not the scope of this blog post. There are many different rules with Indexes and many different scenarios. For example – a table which is heap (no clustered index) is often not recommended on OLTP workload (here is the blog post to identify them), drop unused indexes with careful observation (here is the script for it), identify missing indexes and after careful testing add them (here is the script for it). Even though I have given few links here it is just the tip of the iceberg. If you follow only above four advices your ship may still sink. Those who wants to learn the subject in depth can watch the videos here after logging in. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • The case against INFORMATION_SCHEMA views

    - by AaronBertrand
    In SQL Server 2000, INFORMATION_SCHEMA was the way I derived all of my metadata information - table names, procedure names, column names and data types, relationships... the list goes on and on. I used the system tables like sysindexes from time to time, but I tried to stay away from them when I could. In SQL Server 2005, this all changed with the introduction of catalog views. For one thing, they're a lot easier to type. sys.tables vs. INFORMATION_SCHEMA.TABLES? Come on; no contest there - even...(read more)

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  • Microsoft Access 2010: How to Modify Tables

    As you work with Microsoft Access 2010, it is highly likely that you will run in to times where you need to modify the fields contained within your tables. Luckily, this is a task that is not hard to accomplish, and this tutorial will teach you how to do so. Before you begin modifying tables, you should be aware that there are basically three different ways in which you can affect or control the type of data that enters your fields, which are data types, character limits, and validation rules. We will be taking a look at them today, so let's begin, shall we? Keep in mind that for this tutor...

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  • Microsoft Access 2010: How to Add, Edit, and Delete Data in Tables

    Tables are such an integral part of databases and corresponding tasks in Access 2010 because they act as the centers that hold all the data. They may be basic in format, but their role is undeniably important. So, to get you up to speed on working with tables, let's begin adding, editing, and deleting data. These are very standard tasks that you will need to employ from time to time, so it is a good idea to start learning how to execute them now. As is sometimes the case with our tutorials, we will be working with a specific sample. To learn the tasks, read over the tutorial and then apply...

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  • Fusion Tables API enfocando a los desarrolladores

    Fusion Tables API enfocando a los desarrolladores En este programa presentaremos una visión general de las novedades tecnológicas desde el equipo de relaciones para desarrolladores de la región de sur de Latinoamérica. Seguiremos presentando nuestro enfoque de desarrollo, ingeniería y las mejores prácticas para implementar tecnología Google favoreciendo la evolución de soluciones tecnológicas. Luego nos introduciremos en un escenario técnico en donde analizaremos la solución Fusion Tables API para desarrolladores(seguimos trabajando sobre los entornos de persistencia en la nube). Finalmente estaremos conversando con la comunidad de desarrollo, resolviendo un desafío técnico y premiando todo el talento regional From: GoogleDevelopers Views: 0 1 ratings Time: 00:00 More in Education

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  • Introduction to SQL Server 2014 CTP1 Memory-Optimized Tables

    There are a number of new features that became available with SQL Server 2014. One of the more exciting features is the new Memory-Optimized tables. In this article Greg Larson explores how to create Memory-Optimized tables, and what he's found during his initial exploration of using this new type of table. Countless happy developers. One award-winning bundle.The SQL Developer Bundle can transform the way you and your team work, aiding collaboration, efficiency, and consistency. Download your free trial now.

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  • How to find classes that use certain DB tables

    - by Songo
    Problem: I'm asked to prepare a document where all our DB tables are listed and I'm supposed to list all Controllers that uses these DB tables for read and another list for Controllers that do write operations. Ex: +------------------------------------------+------------+ | DB table | tbl_Orders | +------------------------------------------+------------+ |Controllers that perform read operations | ?? | +------------------------------------------+------------+ |Controllers that perform write operations | ?? | +------------------------------------------+------------+ We are trying to write some documentation for a legacy system built using Zend framework. The code is scattered everywhere. There is code in the Controllers, in the models and even in the views. The application uses PROPEL as an ORM. What makes this really difficult is that the Controller may not be directly calling the table, but it may be instantiating a model class that calls that table. Is there an educated way to approach this crazy task? Note: Searching for the table name won't provide a solution because if a model uses that table I wouldn't know which Controller is using that model.

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  • how to remove or change background fills in all tables in a microsoft word document

    - by PA.
    I have a bunch of large documents, with many tables that have different and inconsistent fill styles - some of them are not readable in black and white when printed. I cannot change the background fill for all the tables at once. The problem I have is that when I open such a document, and Select All, the Table Properties are inactive. Do you know a technique for selecting all the tables, or a method for applying global format of tables, with a script or some other way?

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  • How to Create Views for All Tables with Oracle SQL Developer

    - by thatjeffsmith
    Got this question over the weekend via a friend and Oracle ACE Director, so I thought I would share the answer here. If you want to quickly generate DDL to create VIEWs for all the tables in your system, the easiest way to do that with SQL Developer is to create a data model. Wait, why would I want to do this? StackOverflow has a few things to say on this subject… So, start with importing a data dictionary. Step One: Open of Create a Model In SQL Developer, go to View – Data Modeler – Browser. Then in the browser panel, expand your design and create a new Relational Model. Step Two: Import your Data Dictionary This is a fancy way of saying, ‘suck objects out of the database into my model’ This will open a wizard to connect, select your schema(s), objects, etc. Once they’re in your model, you’re ready to cook with gas I’m using HR (Human Resources) for this example. You should end up with something that looks like this. Our favorite HR model Now we’re ready to generate the views! Step Three: Auto-generate the Views Go to Tools – Data Modeler – Table to View Wizard. I don’t want all my tables included, and I want to change the naming standard Decide if you want to change the default generated view names By default the views will be created as ‘V_TABLE_NAME.’ If you don’t like the ‘V_’ you can enter your own. You also can reference the object and model name with variables as shown in the screenshot above. I’m going to go with something a little more personal. The views are the little green boxes in the diagram Can’t find your views? They should be grouped together in your diagram. Don’t forget to use the Navigator to easily find and navigate to those model diagram objects! Step Four: Generate the DDL Ok, let’s use the Generate DDL button on the toolbar. Un-check everything but your views If you used a prefix, take advantage of that to create a filter. You might have existing views in your model that you don’t want to include, right? Once you click ‘OK’ the DDL will be generated. -- Generated by Oracle SQL Developer Data Modeler 4.0.0.825 -- at: 2013-11-04 10:26:39 EST -- site: Oracle Database 11g -- type: Oracle Database 11g CREATE OR REPLACE VIEW HR.TJS_BLOG_COUNTRIES ( COUNTRY_ID , COUNTRY_NAME , REGION_ID ) AS SELECT COUNTRY_ID , COUNTRY_NAME , REGION_ID FROM HR.COUNTRIES ; CREATE OR REPLACE VIEW HR.TJS_BLOG_EMPLOYEES ( EMPLOYEE_ID , FIRST_NAME , LAST_NAME , EMAIL , PHONE_NUMBER , HIRE_DATE , JOB_ID , SALARY , COMMISSION_PCT , MANAGER_ID , DEPARTMENT_ID ) AS SELECT EMPLOYEE_ID , FIRST_NAME , LAST_NAME , EMAIL , PHONE_NUMBER , HIRE_DATE , JOB_ID , SALARY , COMMISSION_PCT , MANAGER_ID , DEPARTMENT_ID FROM HR.EMPLOYEES ; CREATE OR REPLACE VIEW HR.TJS_BLOG_JOBS ( JOB_ID , JOB_TITLE , MIN_SALARY , MAX_SALARY ) AS SELECT JOB_ID , JOB_TITLE , MIN_SALARY , MAX_SALARY FROM HR.JOBS ; CREATE OR REPLACE VIEW HR.TJS_BLOG_JOB_HISTORY ( EMPLOYEE_ID , START_DATE , END_DATE , JOB_ID , DEPARTMENT_ID ) AS SELECT EMPLOYEE_ID , START_DATE , END_DATE , JOB_ID , DEPARTMENT_ID FROM HR.JOB_HISTORY ; CREATE OR REPLACE VIEW HR.TJS_BLOG_LOCATIONS ( LOCATION_ID , STREET_ADDRESS , POSTAL_CODE , CITY , STATE_PROVINCE , COUNTRY_ID ) AS SELECT LOCATION_ID , STREET_ADDRESS , POSTAL_CODE , CITY , STATE_PROVINCE , COUNTRY_ID FROM HR.LOCATIONS ; CREATE OR REPLACE VIEW HR.TJS_BLOG_REGIONS ( REGION_ID , REGION_NAME ) AS SELECT REGION_ID , REGION_NAME FROM HR.REGIONS ; -- Oracle SQL Developer Data Modeler Summary Report: -- -- CREATE TABLE 0 -- CREATE INDEX 0 -- ALTER TABLE 0 -- CREATE VIEW 6 -- CREATE PACKAGE 0 -- CREATE PACKAGE BODY 0 -- CREATE PROCEDURE 0 -- CREATE FUNCTION 0 -- CREATE TRIGGER 0 -- ALTER TRIGGER 0 -- CREATE COLLECTION TYPE 0 -- CREATE STRUCTURED TYPE 0 -- CREATE STRUCTURED TYPE BODY 0 -- CREATE CLUSTER 0 -- CREATE CONTEXT 0 -- CREATE DATABASE 0 -- CREATE DIMENSION 0 -- CREATE DIRECTORY 0 -- CREATE DISK GROUP 0 -- CREATE ROLE 0 -- CREATE ROLLBACK SEGMENT 0 -- CREATE SEQUENCE 0 -- CREATE MATERIALIZED VIEW 0 -- CREATE SYNONYM 0 -- CREATE TABLESPACE 0 -- CREATE USER 0 -- -- DROP TABLESPACE 0 -- DROP DATABASE 0 -- -- REDACTION POLICY 0 -- -- ERRORS 0 -- WARNINGS 0 You can then choose to save this to a file or not. This has a few steps, but as the number of tables in your system increases, so does the amount of time this feature can save you!

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  • Indexing data from multiple tables with Oracle Text

    - by Roger Ford
    It's well known that Oracle Text indexes perform best when all the data to be indexed is combined into a single index. The query select * from mytable where contains (title, 'dog') 0 or contains (body, 'cat') 0 will tend to perform much worse than select * from mytable where contains (text, 'dog WITHIN title OR cat WITHIN body') 0 For this reason, Oracle Text provides the MULTI_COLUMN_DATASTORE which will combine data from multiple columns into a single index. Effectively, it constructs a "virtual document" at indexing time, which might look something like: <title>the big dog</title> <body>the ginger cat smiles</body> This virtual document can be indexed using either AUTO_SECTION_GROUP, or by explicitly defining sections for title and body, allowing the query as expressed above. Note that we've used a column called "text" - this might have been a dummy column added to the table simply to allow us to create an index on it - or we could created the index on either of the "real" columns - title or body. It should be noted that MULTI_COLUMN_DATASTORE doesn't automatically handle updates to columns used by it - if you create the index on the column text, but specify that columns title and body are to be indexed, you will need to arrange triggers such that the text column is updated whenever title or body are altered. That works fine for single tables. But what if we actually want to combine data from multiple tables? In that case there are two approaches which work well: Create a real table which contains a summary of the information, and create the index on that using the MULTI_COLUMN_DATASTORE. This is simple, and effective, but it does use a lot of disk space as the information to be indexed has to be duplicated. Create our own "virtual" documents using the USER_DATASTORE. The user datastore allows us to specify a PL/SQL procedure which will be used to fetch the data to be indexed, returned in a CLOB, or occasionally in a BLOB or VARCHAR2. This PL/SQL procedure is called once for each row in the table to be indexed, and is passed the ROWID value of the current row being indexed. The actual contents of the procedure is entirely up to the owner, but it is normal to fetch data from one or more columns from database tables. In both cases, we still need to take care of updates - making sure that we have all the triggers necessary to update the indexed column (and, in case 1, the summary table) whenever any of the data to be indexed gets changed. I've written full examples of both these techniques, as SQL scripts to be run in the SQL*Plus tool. You will need to run them as a user who has CTXAPP role and CREATE DIRECTORY privilege. Part of the data to be indexed is a Microsoft Word file called "1.doc". You should create this file in Word, preferably containing the single line of text: "test document". This file can be saved anywhere, but the SQL scripts need to be changed so that the "create or replace directory" command refers to the right location. In the example, I've used C:\doc. multi_table_indexing_1.sql : creates a summary table containing all the data, and uses multi_column_datastore Download link / View in browser multi_table_indexing_2.sql : creates "virtual" documents using a procedure as a user_datastore Download link / View in browser

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  • I need some MySQL lookup table advice

    - by Gary Beam
    I have a MySQL database with about 200 tables. 50 of these are small 2-field 'id-data' lookup tables. Several of these DB's are hosted on a shared server. I have been informed that I need to reduce the total number of tables in the shared hosting environment because of performance issues relating to too many tables. My question is: Could/Should the 50 2-Field lookup tables be combined into a single 3-field table with 'id-field_name-data' Fields? Even if this can be done, I will have a lot of work to do on the PHP user application. My other choice is moving the DB's to a dedicated server at much higher hosting cost. I don't believe my 200 table DB's are actually causing any performance issues on this shared hosting server, at least not from the user application standpoint. There are never more than 10 of these tables joined in any single query; although I have seen some very-slow queries generated by phpmyadmin on these DB's.

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  • Combine two or more tables into a third separate table

    - by Samuel
    Hi community, I have an excel workbook that has three pivot tables in it. What I am wanting to do is create a fourth table that combines the data from all three of the other tables. Essentially I want to concatenate the tables together but still preserve the source tables. Another criteria of what I am wanting to do is if I add a row to any of the source tables it must update the combined table and it must work with x amount of rows where x could be any size. I know I am asking a lot but I would be so grateful if I could get some help working this out. I am comfortable with using either VBA or native excel to solve this. If you guys need examples I will be happy to upload some.

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  • Kill your temp tables using keyboard shortcuts : SSMS

    - by jamiet
    Here’s a nifty little SSMS trick that my colleague Tom Hunter educated me on the other day and I thought it was worth sharing. If you’re a keyboard shortcut junkie then you’ll love it. How often when working with code in SSMS that contains temp tables do you see the following message: Msg 2714, Level 16, State 6, Line 78 There is already an object named '#table' in the database. Quite often I would imagine, it happens to me all the time! Usually I write a bit of code at the top of the query window that goes and drops the table if it exists but there’s a much easier way of dealing with it. Remember that temp tables disappear as soon as your sessions ends hence wouldn’t it be nice if there were a quick way of recycling (i.e. stopping and restarting) your session? Well turns out there is and all it takes is a sequence of 4 keystrokes: Bring up the context menu using that mythically-named button that usually sits 3 to the right of the space bar ‘C’ for “Connection” ‘H’ for “Change Connection…” ‘Enter’ to select the same connection you had open last time (screenshots below) Once you’ve done it a few times you’ll probably have the whole sequence down to less than a second. Such a simple little trick, I’m annoyed with myself for it not occurring to me before! The only caveat is that you’ll need a “USE <database>” directive at the top of your query window but I don’t think that’s much of a bind! That is all other than to say if you like little SSMS titbits like this then Lee Everest’s blog is a good one to keep an eye on! @jamiet Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • More Tables or More Databases?

    - by BuckWoody
    I got an e-mail from someone that has an interesting situation. He has 15,000 customers, and he asks if he should have a database for their data per customer. Without a LOT more data it’s impossible to say, of course, but there are some general concepts to keep in mind. Whenever you’re segmenting data, it’s all about boundary choices. You have not only boundaries around how big the data will get, but things like how many objects (tables, stored procedures and so on) that will be involved, if there are any cross-sections of data (do they share location or product information) and – very important – what are the security requirements? From the answer to these types of questions, you now have the choice of making multiple tables in a single database, or using multiple databases. A database carries some overhead – it needs a certain amount of memory for locking and so on. But it has a very clean boundary – everything from objects to security can be kept apart. Having multiple users in the same database is possible as well, using things like a Schema. But keeping 15,000 schemas can be challenging as well. My recommendation in complex situations like this is similar to a post on decisions that I did earlier – I lay out the choices on a spreadsheet in rows, and then my requirements at the top in the columns. I  give each choice a number based on how well it meets each requirement. At the end, the highest number wins. And many times it’s a mix – perhaps this person could segment customers into larger regions or districts or products, in a database. Within that database might be multiple schemas for the customers. Of course, he needs to query across all customers, that becomes another requirement. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • More Tables or More Databases?

    - by BuckWoody
    I got an e-mail from someone that has an interesting situation. He has 15,000 customers, and he asks if he should have a database for their data per customer. Without a LOT more data it’s impossible to say, of course, but there are some general concepts to keep in mind. Whenever you’re segmenting data, it’s all about boundary choices. You have not only boundaries around how big the data will get, but things like how many objects (tables, stored procedures and so on) that will be involved, if there are any cross-sections of data (do they share location or product information) and – very important – what are the security requirements? From the answer to these types of questions, you now have the choice of making multiple tables in a single database, or using multiple databases. A database carries some overhead – it needs a certain amount of memory for locking and so on. But it has a very clean boundary – everything from objects to security can be kept apart. Having multiple users in the same database is possible as well, using things like a Schema. But keeping 15,000 schemas can be challenging as well. My recommendation in complex situations like this is similar to a post on decisions that I did earlier – I lay out the choices on a spreadsheet in rows, and then my requirements at the top in the columns. I  give each choice a number based on how well it meets each requirement. At the end, the highest number wins. And many times it’s a mix – perhaps this person could segment customers into larger regions or districts or products, in a database. Within that database might be multiple schemas for the customers. Of course, he needs to query across all customers, that becomes another requirement. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • how to diffrentiate between same field names of two tables in a select query??

    - by developer
    i have more than two tables in my database and all of them contains same field names like table A table B table C field1 field1 field1 field2 field2 field2 field3 field3 field3 . . . . . . . . . . . . I have to write a SELECT query which gets almost all same fields from these 3 tables.Iam using something like this :- select a.field1,a.field2,a.field3,b.field1,b.field2,b.field3,c.field1,c.field2,c.field3 from table A as a, table B as b,table C as c where so and so. but when i print field1's value it gives me the last table values. How can i get all the values of three tables with the same field names??? do i have to write individual query for every table OR there is any ways of fetching them all in a single query????

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  • How do I restrict concurrent statistics gathering to a small set of tables from a single schema?

    - by Maria Colgan
    I got an interesting question from one of my colleagues in the performance team last week about how to restrict a concurrent statistics gather to a small subset of tables from one schema, rather than the entire schema. I thought I would share the solution we came up with because it was rather elegant, and took advantage of concurrent statistics gathering, incremental statistics, and the not so well known “obj_filter_list” parameter in DBMS_STATS.GATHER_SCHEMA_STATS procedure. You should note that the solution outline below with “obj_filter_list” still applies, even when concurrent statistics gathering and/or incremental statistics gathering is disabled. The reason my colleague had asked the question in the first place was because he wanted to enable incremental statistics for 5 large partitioned tables in one schema. The first time you gather statistics after you enable incremental statistics on a table, you have to gather statistics for all of the existing partitions so that a synopsis may be created for them. If the partitioned table in question is large and contains a lot of partition, this could take a considerable amount of time. Since my colleague only had the Exadata environment at his disposal overnight, he wanted to re-gather statistics on 5 partition tables as quickly as possible to ensure that it all finished before morning. Prior to Oracle Database 11g Release 2, the only way to do this would have been to write a script with an individual DBMS_STATS.GATHER_TABLE_STATS command for each partition, in each of the 5 tables, as well as another one to gather global statistics on the table. Then, run each script in a separate session and manually manage how many of this session could run concurrently. Since each table has over one thousand partitions that would definitely be a daunting task and would most likely keep my colleague up all night! In Oracle Database 11g Release 2 we can take advantage of concurrent statistics gathering, which enables us to gather statistics on multiple tables in a schema (or database), and multiple (sub)partitions within a table concurrently. By using concurrent statistics gathering we no longer have to run individual statistics gathering commands for each partition. Oracle will automatically create a statistics gathering job for each partition, and one for the global statistics on each partitioned table. With the use of concurrent statistics, our script can now be simplified to just five DBMS_STATS.GATHER_TABLE_STATS commands, one for each table. This approach would work just fine but we really wanted to get this down to just one command. So how can we do that? You may be wondering why we didn’t just use the DBMS_STATS.GATHER_SCHEMA_STATS procedure with the OPTION parameter set to ‘GATHER STALE’. Unfortunately the statistics on the 5 partitioned tables were not stale and enabling incremental statistics does not mark the existing statistics stale. Plus how would we limit the schema statistics gather to just the 5 partitioned tables? So we went to ask one of the statistics developers if there was an alternative way. The developer told us the advantage of the “obj_filter_list” parameter in DBMS_STATS.GATHER_SCHEMA_STATS procedure. The “obj_filter_list” parameter allows you to specify a list of objects that you want to gather statistics on within a schema or database. The parameter takes a collection of type DBMS_STATS.OBJECTTAB. Each entry in the collection has 5 feilds; the schema name or the object owner, the object type (i.e., ‘TABLE’ or ‘INDEX’), object name, partition name, and subpartition name. You don't have to specify all five fields for each entry. Empty fields in an entry are treated as if it is a wildcard field (similar to ‘*’ character in LIKE predicates). Each entry corresponds to one set of filter conditions on the objects. If you have more than one entry, an object is qualified for statistics gathering as long as it satisfies the filter conditions in one entry. You first must create the collection of objects, and then gather statistics for the specified collection. It’s probably easier to explain this with an example. I’m using the SH sample schema but needed a couple of additional partitioned table tables to get recreate my colleagues scenario of 5 partitioned tables. So I created SALES2, SALES3, and COSTS2 as copies of the SALES and COSTS table respectively (setup.sql). I also deleted statistics on all of the tables in the SH schema beforehand to more easily demonstrate our approach. Step 0. Delete the statistics on the tables in the SH schema. Step 1. Enable concurrent statistics gathering. Remember, this has to be done at the global level. Step 2. Enable incremental statistics for the 5 partitioned tables. Step 3. Create the DBMS_STATS.OBJECTTAB and pass it to the DBMS_STATS.GATHER_SCHEMA_STATS command. Here, you will notice that we defined two variables of DBMS_STATS.OBJECTTAB type. The first, filter_lst, will be used to pass the list of tables we want to gather statistics on, and will be the value passed to the obj_filter_list parameter. The second, obj_lst, will be used to capture the list of tables that have had statistics gathered on them by this command, and will be the value passed to the objlist parameter. In Oracle Database 11g Release 2, you need to specify the objlist parameter in order to get the obj_filter_list parameter to work correctly due to bug 14539274. Will also needed to define the number of objects we would supply in the obj_filter_list. In our case we ere specifying 5 tables (filter_lst.extend(5)). Finally, we need to specify the owner name and object name for each of the objects in the list. Once the list definition is complete we can issue the DBMS_STATS.GATHER_SCHEMA_STATS command. Step 4. Confirm statistics were gathered on the 5 partitioned tables. Here are a couple of other things to keep in mind when specifying the entries for the  obj_filter_list parameter. If a field in the entry is empty, i.e., null, it means there is no condition on this field. In the above example , suppose you remove the statement Obj_filter_lst(1).ownname := ‘SH’; You will get the same result since when you have specified gather_schema_stats so there is no need to further specify ownname in the obj_filter_lst. All of the names in the entry are normalized, i.e., uppercased if they are not double quoted. So in the above example, it is OK to use Obj_filter_lst(1).objname := ‘sales’;. However if you have a table called ‘MyTab’ instead of ‘MYTAB’, then you need to specify Obj_filter_lst(1).objname := ‘”MyTab”’; As I said before, although we have illustrated the usage of the obj_filter_list parameter for partitioned tables, with concurrent and incremental statistics gathering turned on, the obj_filter_list parameter is generally applicable to any gather_database_stats, gather_dictionary_stats and gather_schema_stats command. You can get a copy of the script I used to generate this post here. +Maria Colgan

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  • MySql: Query multiple identical dynamic tables.

    - by JYelton
    I have a database with 500+ tables, each with identical structure, that contain historical data from sensors. I am trying to come up with a query that will locate, for example, all instances where sensor n exceeds x. The problem is that the tables are dynamic, the query must be able to dynamically obtain the list of tables. I can query information_schema.tables to get a list of the tables, like so: SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name'; I can use this to create a loop in the program and then query the database repeatedly, however it seems like there should be a way to have MySql do the multiple table search. I have not been able to make a stored procedure that works, but the examples I can find are generally for searching for a string in any column. I want to specifically find data in a specific column that exists in all tables. I admit I do not understand how to properly use stored procedures nor if they are the appropriate solution to this problem. An example query inside the loop would be: SELECT device_name, sensor_value FROM device_table WHERE sensor_value > 10; Trying the following does not work: SELECT device_name, sensor_value FROM ( SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name' ) WHERE sensor_value > 10; It results in an error: "Every derived table must have its own alias." The goal is to have a list of all devices that have had a given sensor value occur anywhere in their log (table). Ultimately, should I just loop in my program once I've obtained a list of tables, or is there a query structure that would be more efficient?

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