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FAQ - Pivotal Greenplum Limits

Goal

This article will take a look at some common frequently asked question on Pivotal Greenplum limit.

Solution

1. What are some of the limit in the Pivotal Greenplum?

Dimension Limit
Maximum size for a database? unlimited
Maximum size for a table? unlimited, 128 TB per partition per segment
Maximum size for a row? >1 GB (approximate)
Maximum size for a field? 1 GB
Maximum BLOB size 1 GB (Use BYTEA datatype, we don't have BLOB)
Maximum number of rows in a table? 2^48
Maximum number of columns in a table? 1600
Maximum number of indexes on a table? unlimited
Maximum number of databases/users unlimited
Maximum number of tables per database 4200 million
Maximum number of columns per View unlimited
Maximum length of column/table/database name 63
Maximum number of columns per index unlimited
Maximum number of table level constraints per table unlimited
Maximum active concurrent transactions unlimited
Maximum data format descriptor size 63 characters
Maximum database, user, base table, view, index, trigger, stored procedure, UDF, UDT, constraint or column name size. 63 characters
Maximum sessions per parsing engine No concept of parsing engine other than masterDB node. No fixed limit, up to a few hundred.
Maximum columns per primary and secondary index 32  

2. What is the MAX number of columns that can be present in the SELECT statement ?

1664

3. What is the MAX number of URL's that can be placed in the LOCATION part of the external table creation ?

eg.s

CREATE EXTERNAL TABLE ext3 ( a int )
LOCATION ('gpfdist://mdw:8081/a1','gpfdist://mdw:8081/a2',.....,'gpfdist://mdw:8081/a999',) FORMAT 'TEXT' (DELIMITER '|');

There is no upper limit for the max number of URL's that can be added to the LOCATION clause , what restrict is the amount of size the location clause which is 32712 (32KB) , if you exceed you might hit with the error

ERROR:  row is too big: size 42872, maximum size 32712

So if you planning to add many URL's in the Location clause , would recommend to move them on to a separate folder and start the gpfdist file server program in the background using

gpfdist -p 8081 -d <file_location> -l /home/gpadmin/log &

and write the create external command ( to the one below ) to read all the files in the location

CREATE EXTERNAL TABLE ext3 ( a int )
 LOCATION ('gpfdist://mdw:8081/*') FORMAT 'TEXT' (DELIMITER '|');

Also another limit is the FORMAT clause can take in only 8191 bytes , if you exceed you may end up with error

"ERROR: format options must be less than 8191 bytes in size". 

4. What is the max text length of the SQL statement ?

No limit , but we (Pivotal Greenplum) do control the length of the text using the max_stack_depth parameter and OS control it using the stack limit defined by unix stack size , so if the customer has a bigger text , then increase the stack size from the OS first and then alter the max_stack_depth in greenplum and restart the database after each changes , since to take advantage of the new stack size , the green plum process needs to be recycled.

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