[
https://issues.apache.org/jira/browse/NIFI-1706?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16198363#comment-16198363
]
ASF GitHub Bot commented on NIFI-1706:
--------------------------------------
Github user patricker commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2162#discussion_r143664137
--- Diff:
nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/AbstractDatabaseFetchProcessor.java
---
@@ -240,7 +254,14 @@ public void setup(final ProcessContext context) {
// Try a query that returns no rows, for the purposes of
getting metadata about the columns. It is possible
// to use DatabaseMetaData.getColumns(), but not all drivers
support this, notably the schema-on-read
// approach as in Apache Drill
- String query = dbAdapter.getSelectStatement(tableName,
maxValueColumnNames, "1 = 0", null, null, null);
+ String query;
+
+ if(StringUtils.isEmpty(sqlQuery)) {
+ query = dbAdapter.getSelectStatement(tableName,
maxValueColumnNames, "1 = 0", null, null, null);
+ } else {
+ query=sqlQuery + " WHERE 1=0";
--- End diff --
@mattyb149
> If they specify a max-value column in the other property, and it is not
available in this query, then the getSelectStatement() below doesn't seem like
it would work as expected
What about if I take the list of maxValueColumns and use those to build the
equivelant of the "1=0" condition. For example, if our max value column names
are `x` and `y` I could build a where expression `x <> x AND y <> y`. This
would ensure the column names were present, and if they aren't an exception
would be thrown.
> Extend QueryDatabaseTable to support arbitrary queries
> ------------------------------------------------------
>
> Key: NIFI-1706
> URL: https://issues.apache.org/jira/browse/NIFI-1706
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Affects Versions: 1.4.0
> Reporter: Paul Bormans
> Assignee: Peter Wicks
> Labels: features
>
> The QueryDatabaseTable is able to observe a configured database table for new
> rows and yield these into the flowfile. The model of an rdbms however is
> often (if not always) normalized so you would need to join various tables in
> order to "flatten" the data into useful events for a processing pipeline as
> can be build with nifi or various tools within the hadoop ecosystem.
> The request is to extend the processor to specify an arbitrary sql query
> instead of specifying the table name + columns.
> In addition (this may be another issue?) it is desired to limit the number of
> rows returned per run. Not just because of bandwidth issue's from the nifi
> pipeline onwards but mainly because huge databases may not be able to return
> so many records within a reasonable time.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
