The Presto query engine has some limitations compared to Hive at this stage. We welcome your feedback and will make improvements based on these.
Table of Contents
Column Name Escaping
When a column name matches the name of a reserved keyword, the name of the columns needs to be quoted. While in Hive, as most the SQL-based query languages, the quotation character is the back tick character `, in Presto quoting of a column name is accomplished with the double quote character instead “. See the comparison below:
SELECT `join` FROM mytbl # Hive SELECT "join" FROM mytbl # Presto
Please be aware that quoting a column name in single quotes ‘ will make the query parser interpret the content as a simple string producing a perhaps unexpected result:
SELECT "join" FROM mytbl LIMIT 10 result: value1 value2 value3 value4 ... value10 SELECT 'join' FROM mytbl result: join join join join ... join
Table Schemas are Required
When querying via Presto, you must set a Schema for the table(s); the
v syntax doesn’t work.
Presto does not currently support cost-based JOIN optimizations, meaning JOINs are not automatically reordered based on table size. Please make sure that smaller tables are on the right hand size of JOIN, and they must fit in memory. Otherwise out of memory exceptions will cause the query to fail.
SELECT ... FROM large_table JOIN small_table
INSERT OVERWRITE Statements are NOT Supported
Presto does not currently support INSERT OVERWRITE Statements. Please delete table before INSERT INTO.
Last modified: Jun 09 2015 09:17:18 UTC