SQL Server 2014 :: Memory Optimized Tables And Indexes
Feb 18, 2015
I'm just beginning to experiment with memory optimised tables.
I have two sets of near identical tables - one set normal, the other set memory optimised with DURABILITY=SCHEMA_ONLY - and am running test queries against these. When I say that the two sets are "near identical", I mean that they are the same except for the primary keys: for the normal tables these are defined as PRIMARY KEY CLUSTERED whereas for the memory-optimed ones they are defined as PRIMARY KEY NONCLUSTERED HASH WITH (BUCKET_COUNT=nnnn) as per the requirements for such tables.
I then run a pair of test queries, again identical but one referencing the normal tables and the other referencing the memory optimised ones.
(The query uses an inner join on three tables with row counts of approx 3m rows, 100000 rows and 5000 rows.)
The query against the normal tables runs noticeably faster than that against the memory optimised ones. To try to find out why, I examined the execution plans. the plan for the memory optimised query suggests that I have a missing index: but of course I can't create this againsty a memory optimised table. Is this a bug or am I missing something? Why the performance between the two should be so different?
- An MSSQL 2014 Standard server that houses multiple small databases (in excess of a hundred). - These databases are frequently dropped and restored by an application that uses this SQL Server. - There is a business need for this setup at this time, so I can't get away from it. Therefore answers like "don't have so many small databases that are frequently dropped and restored" would be somewhat unuseful
This is the problem I have:
- When I connect SSMS 2014 to the server and expand the "Databases" node, it takes forever to display. In comparison, SSMS 2008 connected to SQL 2008R2 server with the same number of databases displays the Databases tree very quickly.
I ran a trace to see what exactly SSMS 2014 is doing. When the "Databases" node is expanded, it runs a query that checks each database for Memory-Optimized Tables (new and wonderful feature of SQL 2014 for sure, but I'm not using it, at least yet). Naturally, when you have to loop through over a hundred DBs, it takes time. Worse yet, if one of these DBs is in process of being restored, the query sits and waits to time out before proceeding to the next DB. Sometimes this causes outright timeouts. Here is the query:
use [MyDatabase] SELECT ISNULL((select top 1 1 from sys.filegroups FG where FG.[type] = 'FX'), 0) AS [HasMemoryOptimizedObjects]
To be sure, this is NOT a SQL Server performance issue. This server processes a rather heavy workload and has been doing so for over a month, and the workload completes within expected time limits or better. Even so I've done some basic performance measuring, and the server itself is quite all right.
Moreover, if I connect SSMS 2008 to it, I get an error message (Index out of bounds or somesuch), but SSMS 2008 does connect, and displays the Databases tree much faster than SSMS 2014.
I'd like to turn off the option to check for Memory Optimized Objects altogether, as I'm not using the feature.
CREATE TABLE [Sales].[Test_inmem] ( [c1] [int] NOT NULL, [c2] [nvarchar](20) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [ModifiedDate] [datetime2](7) NOT NULL CONSTRAINT [IMDF_Test_ModifiedDate] DEFAULT (sysdatetime()),
[Code] ....
I have to generate 1000000 random records into it. I tried various ways to insert records, but not being a developer could not do it. I hope to make the C1 as a serial number, C2 can be anything, C3 I want to be the timestamp.
How do i find Total allocated space and used space of a memory optimized filegroup?
use memory_optimized_db Go select (SUM(size)*8.0)/1024.0 as Space, FILEGROUP_NAME ( data_space_id ) , type_desc from sys.database_files group by data_space_id,type_desc;
above query gives "current used size of the container " of memory optimized file group but doesn't give Total space detail.
I've been having some trouble getting a single-column "varchar(5)" field to reliably use a table seek instead of a table scan. The production table in this case contains 25 million rows. As impressive as it is to scan 25 million rows in 35 seconds, the query should run much faster.
Typically, this table is accessed with a query that includes:
SELECT ... FROM SummaryTable WHERE ixZIP IN (SELECT ZipCode FROM @ZipCodesForMO)
This query insists on using a table scan. I've tried WITH (FORCESEEK) for example, but that just makes the query fail.
As I've investigated this issue I also tried:
SELECT * FROM Summaries WHERE ZipCode IN ('xxxxx', 'xxxxx', 'xxxxx')
When I run this query with 64 or fewer (actual, valid) ZIP codes, the query uses a table seek.But when I give it 65 or more ZIP codes it uses a table scan.
To summarize, the production query always uses a table scan, and when I specify 65 or more ZIP codes the query also uses a table scan. I'm wondering if the data type of the indexed column (Latin1_General_100_BIN2) is somehow the problem. I'll likely try converting the ZIP codes to an integer to see what happens.
I try to load data into a memOpt table (INSERT INTO ... SELECT ... FROM ...). The source table has a size about 1 Gb and 13 Mio Rows. During this load the LDF File grows to size of 350 GB (until the space if the disk is run out of space). The Server has about 110 GB Memory for the SQL Server reserved. The tempdB doesn't grow. The Bucket Size in the create statement has a size of 262144. The Hash key as 4 fields`(2 fields have the datatype int,1 has smallint, 1 has varchar(200). ) The disk for the datafiles has still space for the datafiles (incl. the hekaton files).
How can I reduce the size of the ldf files during the load of the data ?
We are planning to upgrade. We are using Sql 2008R2 now. Which is the better option migrating to SQL 2012 or migrating to 2014?I am thinking 2014 has memory optimized tables and updatable column stored index. So it is better option.
I've a database with a memory optimized filegroup on it. How can I remove it?I have removed the memory optimized table I had on it, but when I try to remove the filegroup I receive an error.
I have inherited a database that is over-indexed, i.e. there are sometimes 10-20 indexes on a table. The performance is at times not great due to blocking from long running queries. I want to clean up the indexes as a starting point.
Through a query I found some time ago on the SQLCat blog I have discovered a large number of indexes in the database that have a huge disparity between reads and writes. The range of difference is sometimes almost 2 million more writes than reads. Should I just drop the indexes that have say, more than 100,000 more writes than reads and then see what the Missing Index DMVs tell me after a few days of running without those indexes?
In some cases there are a few hundred thousand reads but maybe a million writes on the index. Thus, there are a fair number of reads happening, just not in comparison to the number of writes. In some cases there are almost no reads and a million or more writes. I am obviously dropping those indexes. I just am not sure what to do about the indexes that do have a fair number of reads.
I've been trying to get a definitive answer to this question but alas I have conflicting and patchy answers so far from other sources. I have an index that, lets say, requires 10GB of data space to rebuild..This index resides on a filegroup that spans 2 files on two seperate drives (i.e. a mdf and ndf)
When I rebuild this index how will each of these datafiles grow as the rebuild proceeds to completion? Lets for the time being remove the caveats of any other activity hitting the example index/database in question.My tests seem to show that only the mdf will grows (or the file with the lowest id in the that filegroup) provided there is enough space available in that particular file to complete the operation. The secondary ndf dat file doesnt grow at all if the mdf has enough space.
Is expected behavior? i.e. the index will be rebuilt in a contiguous manner relative to the files contained with the filegroup i.e. fileid 1 will grow till limit reached then next fileid grows etc?
My database server memory utilisation is growing faster from past 1 week. it remained same for 1 week around 55% and now it is going to 70% and increasing.
Total OS memory is 32GB and I kept cap for sql server memory upto 29GB. Dont know what to do..
I am doing a performance testing for In-memory option is sql server 2014. As a part I want to insert 500 million rows of records into a in-memory enabled test table I have created.
I need a sample script to insert 500 million records into a table ....
We have run into an issue on a dedicated SSAS 2012 SP1 server where the allocated memory is not being utilized, causing some slowness in use, connections, and queries.
Total Memory on the server is 512, and after startup, the utilized memory gets up to a max of 60GB and stops there. Checking the Resource Monitor, msmdsrv.exe is only taking around 39GB overall. With the current properties, that should be at 330GB. Am I missing something in the settings or in configuration that should be changed?
Version: SQL Server 2012 SP1 Enterprise (11.0.3000) OS: Windows Server 2012 Datacenter - Fully patched and up to date Databases: 2 Tabular models Server: 512GB RAM
I'm working on a large scale project that is currently in production. We have a big process that recently changed to use In-Memory Tables with SQL 2014 for performance efficiency.
The Process uses:
51 In-Memory SQL Tables. 50 Stored Procedures (not native) that loads data(Insert) from about 150 regular Tables and IM tables. 300 Validations (short stored procedure not native) Selecting from those 50 In-Memory Tables (And insert to In-Memory table that save the validation errors if exists on In-Memory table).
At the end of this process we clean the table from the data that relavnt to etch prosses(DELETE FROM WHERE)
B.T.W No UPDATE STAT on In-Memory are used-when we test the prosses it slow as down and cause some locks.
We are calling this process from ADO.Net, loads stored procedure first and then validations, each SP use different SQL Connection. In normal use, everything works fine and takes about 1.5 second.
Under stress test (6 Clients X 100 Tasks) for 30 minutes. After several minutes we are starting to get this SQL Exception (1 SQL Exception for every 20 tasks):
41301. A previous transaction that the current transaction took a dependency on has aborted, and the current transaction can no longer commit.
Transactions in Memory-Optimized Tables
The Exception is not clear. We are not using BEGIN TRANSACTION in the process. The SQL Exception occurs in different stored procedures each time.
NODE1 -256GB INST1 - 64GB min/64GB max INST2 - 64GB min/64GB max NODE2 - 256GB INST3- 64GB min/64GB max INST4- 64GB min/64GB max
With this configuration and if all instances are running on the same node there will be enough memory for them to run. Knowing that normally i ll have only 2 instances in each node wouldnt it be better the following config?
NODE1 -256GB INST1 - 64GB min/128GB max INST2 - 64GB min/128GB max NODE2 - 256GB INST3- 64GB min/128GB max INST4- 64GB min/128GB max
With this configuration and in case all the instances (due to a failure) start running on only 1 node, SQL will adjust all instances to just use Min memory specified?
Hello, I have a question about indexes and memory. I was told by an Oracle DBA that told me that Oracle can put commonly used indexes into memory. I know that SQL Server caches indexes, but I don't know how long it stays in memory. Does anyone know when a cached index is dropped from memory? And, I don't know if you can put indexes directly into memory.
If anyone can comment on this, I would greatly appreciate this.
hi, if exists (select * from sysobjects where id = object_id('dbo.MRDD_FINAL') and sysstat & 0xf = 3) drop table dbo.MRDD_FINAL
This code was generated when I used the create a script to build a table from an existing table. is there a way to check if a a table contains data or not, The whole idea is to check if table A contains data, I need to truncate the table,otherwise I do nothing... regards
I had to reinstall my local copy of SQL a few weeks ago, which naturally overwrote the
msdb.dbo.sysmanagement_shared_server_groups_internal and msdb.dbo.sysmanagement_shared_registered_servers_internal tables.
However I still have the local XML file that SSMS reads so I can still access the groups, I just get weird errors when trying to re-register my install as the new CMS. How to rebuilt those tables from the XML file or know of a way to repopulate?
