Abraham Elmahrek created SQOOP-2301:
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Summary: Sqoop2: Document how generic jdbc connector generates sql
Key: SQOOP-2301
URL: https://issues.apache.org/jira/browse/SQOOP-2301
Project: Sqoop
Issue Type: Bug
Reporter: Abraham Elmahrek
Fix For: 2.0.0
There's a lot more information that can added in the {{Connectors.rst}} doc.
There is a lot of overlap in terms of how some of the SQL is generated for
boundary query and the general queries. Here's some information that can be
added:
# {{table name}} - the name of the table to transfer data from
# {{columns}} - a list of columns to pull from the db
# {{query}} - SQL statement for querying the data.
# {{boundary query}} - SQL statement for defining the boundaries.
# {{Partition column}} - Used for partitioning.
*{{table name}}, {{columns}}, and {{query}}*
Sqoop2 will generate SQL automatically when {{table name}} is provided. {{table
name}} and {{columns}} are intended to be used together. If {{query}} is
specified, {{table name}} should not be specified.
*{{boundary query}}*
Sqoop2 will generate SQL for the {{boundary query}} if not specified. The
boundary query is used to define a floor and ceiling for the input splits.
These splits define ranges that will be applied to the {{partition column}}. If
{{table name}} is specified, then the SQL generated will take on the form:
{code}SELECT MIN(`partition column`), MAX(`partition column`) FROM `table
name`{code}
If {{query}} is specified, then the generated SQL will take on the form:
{code}SELECT MIN(`partition column`), MAX(`partition column`) FROM (SELECT ...
FROM ... WHERE 1 = 1) SUBQUERY{code}
*{{partition column}}*
The {{partition column}} will automatically be the private key of the table if
not specified.
*Aliases*
Aliases can be used in custom SQL, but keep in mind how the other generated SQL
statements will be used.
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