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Be Careful with the Sequence CACHE Value

Jim Knicely authored this tip. The default session cache for a sequence is 250,000. Although you can change the cache value of a sequence, setting the value too low can adversely affect performance! dbadmin=> CREATE SEQUENCE default_cache; CREATE SEQUENCE dbadmin=> CREATE SEQUENCE non_default_cache CACHE 5; CREATE SEQUENCE dbadmin=> \timing on Timing is on. dbadmin=> CREATE...

Faster CTAS Statements: Quick Tip

Jim Knicely authored this tip. In a CREATE TABLE statement, you can specify an AS clause to create a table from a query (a.k.a. CTAS statement). When dealing with a large SELECT statement result set, your CTAS should perform much better if you specify the DIRECT load method! dbadmin=> SELECT TO_CHAR(COUNT(*), '999,999,999,999') row_count FROM smaller_table;...

Analyze Statistics at the Schema Level (Part 2): Quick Tip

Jim Knicely authored this tip. The ANALYZE_STATISTICS function only accepts a table/projection/column name as input. In yesterday’s Vertica Quick Tip we learned how to get Vertica to generate and execute ANALYZE_STATISTICS SQL statements, one for each table in a given schema. It was an okay solution, but not very convenient. A better option would be...

Analyze Statistics at the Schema Level (Part 1): Quick Tip

Jim Knicely wrote this tip. The ANALYZE_STATISTICS function collects and aggregates data samples and storage information from all nodes that store projections associated with the specified table. The function accepts a table/projection/column name as input. What if you wanted to get stats for all of the tables in a schema? One option is to have...

What Version of Vertica am I Running?

Jim Knicely authored this tip. The built-in VERSION function returns a VARCHAR that contains your Vertica node's version information. The Vertica version is formatted as X.Y.Z-R, where… • X.Y is the two-digit Vertica major release number, e.g., 8.1, 9.0 and 9.1 • Z is the service pack number, e.g., 7.2.3, 8.1.1 and 9.0.1 • R...
Three 3D arrows, different colors pointing in different directions

Which One of these Nodes Doesn’t Belong? A Vertica Quick Tip

Jim Knicely wrote this tip. We strongly recommend that you use a homogeneous hardware configuration for your Vertica cluster: Each node of the cluster should be similar in CPU, clock speed, number of cores, memory, and operating system version. We learned in the last Vertica Quick Tip that the V_CATALOG.HOST_RESOURCES system table provides a snapshot...

Getting your Node Hardware Specs: Quick Tip

Jim Knicely wrote this tip. At some point in the future, you might not remember the number of CPU sockets/processor cores and the amount of memory on each node of your Vertica cluster. Instead of having to issue several Linux commands on each node, Vertica provides the V_CATALOG.HOST_RESOURCES system table, which provides a snapshot of...
Programmer

SQL Reserved Words: Quick Tip

Jim Knicely authored this tip. Keywords are words that have a specific meaning in the SQL language. Every SQL statement contains one or more keywords. Many keywords are also reserved words. Vertica recommends that you not use reserved words as names for objects, or as identifiers. Including reserved words can make your SQL statements confusing....

Loading Negative (BC) Dates: Quick Tip

Jim Knicely authored this tip. I was asked recently how to load a negative date (one representing a BC date) into Vertica. Although negative dates are not valid in Vertica, the FILLER parameter of the COPY command can be used to load them. dbadmin=> \! cat /home/dbadmin/date.txt -4712-01-01 00:00:00 dbadmin=> COPY public.test FROM '/home/dbadmin/date.txt' REJECTED...

Superfast Table Copy (Revisited): Quick Tip

Jim Knicely authored this tip. You learned from a Vertica Quick Tip back on 02/07/2018 that Vertica has the lightweight, in-memory COPY_TABLE function. This awesome function lets us copy huge tables in less than a second. I wanted to revisit this awesome feature to point out that when using the COPY_TABLE command, if the target...

Handling OLE DB Square Brackets: Quick Tip

Jim Knicely authored this blog. Many Microsoft products, including SSAS, can connect to Vertica using the Vertica OLE DB driver for Windows which is installed as part of the Client Drivers and Tools for Windows. Unfortunately tools like MS SSAS can include square brackets to qualify identifiers in the queries it generates to run in...

Vertica Quick Tip: Monitoring Changes to Configuration Parameters

Jim Knicely authored this tip. The CONFIGURATION_CHANGES system table records the change history of system configuration parameters. This information is useful for identifying: • Who changed the configuration parameter value • When the configuration parameter was changed • Whether nonstandard settings were in effect in the past dbadmin=> SELECT event_timestamp, user_name, parameter, value FROM configuration_changes...