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.
---
