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Questions tagged [columnstore]

An index where data is stored by columns as compared to the traditional storage by rows. This enables much higher data compression saving time on disk I/O and also makes analytics queries much faster since they typically aggregate and group data by columns.

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What is a columnstore index and how is different from clustered and non-clustered indexes?

I am confused about the columnstore index. What is a columnstore index, and how it is different from clustered and non-clustered indexes?
Dilip Kr Singh
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Does order of the columns in columnstore index matters in SQL Server 2012

I have a table with ~200 million rows and ~15 columns in it. I am planning to create the column store index on my table. Will there be any change in performance based on the order of columns that I use in the column store index? If Yes, what is the…
Vinay Kumar Chella
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Why is columnstore index not being used

I have a non-clustered columnstore index on all columns a 40m record non-memory optimized table on SQL Server 2016 Enterprise Edition. A query forcing the use of the columnstore index will perform significantly faster but the optimizer continues to…
Rory
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Column has a data type that cannot participate in a columnstore index

I want to create a clustered columnstore index in a table using the following query: CREATE CLUSTERED COLUMNSTORE INDEX cci ON agl_20180319_bck And I am getting this error: Msg 35343, Level 16, State 1, Line 6 The statement failed. Column…
alexithymia
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Best possible ways to disable index before insert operation and enable back Index after insert

I'm planning to create a Non-clustered columnstore index on SQL Server 2014. But non clustered column store index is read-only and cannot perform DML operations, we need to disable before insert and enable back after insert. What are the best…
Jay Nani
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How to create primary keys in ClickHouse

I did found few examples in the documentation where primary keys are created by passing parameters to ENGINE section. But I did not found any description about any argument to ENGINE, what it means and how do I create a primary key. Thanks in…
Yuriy Nazarenko
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SQL Replace All Tables with Clustered Columnstore Index

We are conducting a migration project, and looking to replace most Rowstore indexes with Clustered Columnstore indexes for large Data Warehouse. We are adding a unique index on the identity column. Does anyone have script to alter run through all…
user11156893
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How to optimize SQL Server Columnstore Alignment

I have a Clustered Columnstore Index Table for our IOT metrics (timeseries data). It contains more than 1 billion rows and structured like this: CREATE TABLE [dbo].[Data]( [DeviceId] [bigint] NOT NULL, [MetricId] [smallint] NOT NULL, [TimeStamp]…
Ted van der Veen
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How does columnar database optimization differ from relational database optimization?

I have the following database structure, stored in a relational database: Two fact tables with ~80 million rows each Three dimension tables that have between 300,000 - 500,000 rows Both fact tables have 3 foreign keys that are used to join to the…
Nick Morgan
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Is a table with lots of columns still an anti-pattern when using clustered column storage index in SQL Server 2014?

Reading about clustered column store index in SQL Server 2014, I'm wondering if having a table with a huge number of columns is still an anti-pattern. Currently to alleviate the problem of having a single table with lots of columns I'm using…
marcob
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Query to identify if current SQL Server version supports columnstore indexes

I have a stored procedure that creates some dynamic tables. If columnstore indexes are supported on the host version of SQL Server then I want to create a columnstore index, otherwise fallback to creating just a normal row store index. I have found…
Mark Robinson
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SQL Server 2012: performance columnstore index vs B-tree

One of the benefits of a columnstore-index is that the data of a single column is stored "next to each other on disk". This stands for better compression and faster read times. However; when using a B-tree (a regular non-clustered index), aren't the…
Gurdt
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How columnstore index knows which data from one column are connected to data from other columns?

I am new to the use of columnstore index. The new different structure of columnstored data raised a question. How we know which data from one column1 (page1) are connected to other column2 (page2). For example if we have the following…
alexithymia
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How to check if a table has columnstore index?

I need to make some mechanism that checks if a table X is columnstored or not and if it is not to convert it. I am aware that to convert a table X for example to clustered columnstore index we can use the following code: CREATE CLUSTERED…
alexithymia
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Is it possible in clickhouse to store a HyperLogLog / uniqState() state directly trough an insert query?

We can use an AggregatedMergeTree table engine, which can be used for a aggregating rows. Generally in aggregated data we are not interested in storing all unique identifiers and still want to do a count distinct. Still we want to have the ability…
RoyB
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