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SQOOP-962: Document null string behavior

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(Venkat Ranganathan via Jarek Jarcec Cecho)
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Jarek Jarcec Cecho 2013-03-21 20:50:26 -07:00
parent a0a03d7f31
commit 7048ca3023
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src/docs/user/connectors.txt
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@ -310,3 +310,59 @@ $ sqoop export \
--export-dir hdfsdir \
--input-fields-terminated-by "\t"
----
Null string handling
^^^^^^^^^^^^^^^^^^^^
Netezza direct connector supports the null-string features of Sqoop. The null
string values are converted to appropriate external table options during export
and import operations.
.Supported export control arguments:
[grid="all"]
`----------------------------------------`---------------------------------------
Argument Description
---------------------------------------------------------------------------------
+\--input-null-string <null-string>+ The string to be interpreted as\
null for string columns.
+\--input-null-non-string <null-string>+ The string to be interpreted as\
null for non string columns.
---------------------------------------------------------------------------------
In the case of Netezza direct mode connector, both the arguments must be
left to the default values or explicitly set to the same value. Furthermore
the null string value is restricted to 0-4 utf8 characters.
On export, for non-string columns, if the chosen null value is a valid
representation in the column domain, then the column might not be loaded as
null. For example, if the null string value is specified as "1", then on
export, any occurrence of "1" in the input file will be loaded as value 1
instead of NULL for int columns.
It is suggested that the null value be specified as empty string for
performance and consistency.
.Supported import control arguments:
[grid="all"]
`----------------------------------------`---------------------------------------
Argument Description
---------------------------------------------------------------------------------
+\--null-string <null-string>+ The string to be interpreted as\
null for string columns.
+\--null-non-string <null-string>+ The string to be interpreted as\
null for non string columns.
---------------------------------------------------------------------------------
In the case of Netezza direct mode connector, both the arguments must be
left to the default values or explicitly set to the same value. Furthermore
the null string value is restricted to 0-4 utf8 characters.
On import, for non-string columns, the chosen null value in current
implementations the null value representation is ignored for non character
columns. For example, if the null string value is specified as "\N", then on
import, any occurrence of NULL for non-char columns in the table will be
imported as an empty string instead of '\N', the chosen null string
representation.
It is suggested that the null value be specified as empty string for
performance and consistency.