What ANALYZE_STATISTICS will do?

         ANALYZE_STATISTICS is a DDL operation that auto-commits the current transaction, if any. The ANALYZE_STATISTICS function reads a fixed, 10 percent of disk contents to aggregate sample data for statistical analysis. To obtain a larger (or smaller) data sampling, use the ANALYZE_HISTOGRAM function, which lets you specify the percent of disk to read. Analyzing more that 10 percent disk space takes proportionally longer to process but results in a higher level of sampling accuracy. ANALYZE_STATISTICS is supported on local temporary tables, but not on global temporary tables.

For more information: Click Here

What is DBD in Vertica?

    The Database Designer is a tool that recommends a physical database design (projections) that provides the best performance to answer your query needs. This is useful because it minimizes the time the DBA spends on physical database tuning and provides the ability to re-design the database incrementally to optimize for changing workloads over time.

You can run the Database Designer before or after a Vertica database has been deployed, and it runs as a background process.

When you use the Database Designer to create a design, the DBA provides the following inputs:

·                     Logical schema (CREATE TABLE statements)

·                     Sample data

·                     A sample set of queries that represent what you'd normally run

·                     A K-safety level

For More Info:

https://my.vertica.com/docs/5.0/HTML/Master/14415.htm

What is Hash-Segmentation and Unsegmented?

Hash-Segmentation:

    Segments a projection evenly and distributes the data across nodes using a built-in hash function. Creating a projection with hash segmentation results in optimal query execution. HP Vertica recommends segmenting large tables.

Unsegmented:

    Automatically replicates the unsegmented projection on each node. To perform distributed query execution, HP Vertica requires an unsegmented copy of each small table superprojection on each node.

What is K-Safe in Vertica?

      Vertica uses the concept of K-Safety for failure recovery. The K value represents the maximum number of nodes in a database that can fail and recover with no loss of data. In Vertica, the value of K can be zero (0), one (1), or two (2). The Physical Schema design must meet certain requirements. To create designs that are K-Safe, Vertica recommends using the Database Designer.

To determine the number of nodes required to meet your K-Safety needs, use the formula: K<N/2

where :

·                     K is the K-Safety value.

·                     N is the number of nodes.

The value of K can be 1 or 2 only when the physical schema design meets certain redundancy requirements. See Physical Schema. To create designs that are K-Safe, Vertica recommends that you use the Database Designer.

By default, Vertica creates K-Safe superprojections when the database has a K-Safety greater than 0 (K>0). When creating projections with the Database Designer, projection definitions that meet K-Safe design requirements are recommended and marked with the K-Safety level. Note the output from running the optimized design script generated by the Database Designer in the following example:

Table and Projection are physical or logical?

Table:
    Tables do not occupy any physical storage at all in Vertica.

Projection:
    Physical storage consists of collections of table columns called projections.

What is Projection?

Optimized collections of table columns that provide physical storage for data. A projection can contain some or all of the columns of one or more tables. A projection that contains all of the columns of a table is called a super-projection. A projection that joins one or more tables is called a pre-join projection.

Vertica Interview Questions

1. What is WOS in Vertica?
2. What is ROS in Vertica?
3. What is Tuple Mover (TM) in Vertica? 
4. What is Projection?
5. Table and Projection are physical or logical?
6. What is K-Safe in Vertica?
7. What is Hash-Segmentation and Unsegmented?
8. What is DBD in Vertica?
9. What ANALYZE_STATISTICS will do?
10. What is Copy Command in Vertica?
11. Howto monitor Copy Command?
12. What is Mergeout in Vertica?
13. What is Encoding and Compression in Vertica?
14. How to find currently running sessions?
15. How to Close/Kill currently running session?

See also:

DB User:

• User Creation
• GRANT USAGE ON SCHEMA PUBLIC
• Create Schema
• Grant usage privileges on a schema to the user
• Grant all privileges on a schema to the user
• Set default search path
• Change Vertica User Privileges from Existing User to New user
• Execute Permissions on User Defined Functions For New Users
• Grant Execute Permissions on ODBC

Vertica Table

• Creation
• Rename Table, Table Column Or View in Vertica
• Projection Creation
• Create A New Table Using Existing Table
• Create Table Partitions
• Change the Owner of Table
• Drop Partition

Sequence:

• Create Sequence Number
• Alter Sequence
• Drop Sequence
• Add Sequence Or Set Default value to a table
• Drop Default Or Sequence on a Table
• Change the Owner of Sequence

Vertica Sessions

• Close Session in Vertica
• Currently Running Sessions in Vertica