@Matt Burgess JDBC spec does state that REAL maps to (single-precision) float; FLOAT maps to double precision, thus the mapping to in avro should be to double not float, reference table B-1 page 190: http://download.oracle.com/otn-pub/jcp/jdbc-4_3-mrel3-eval-spec/jdbc4.3-fr-spec.pdf So the following code fix resolved the issue. https://github.com/apache/nifi/blob/master/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/util/JdbcCommon.java#L527 original case FLOAT: case REAL: builder.name(columnName).type().unionOf().nullBuilder().endNull().and().floatType().endUnion().noDefault(); break; case DOUBLE: builder.name(columnName).type().unionOf().nullBuilder().endNull().and().doubleType().endUnion().noDefault(); break; Modified case REAL: builder.name(columnName).type().unionOf().nullBuilder().endNull().and().floatType().endUnion().noDefault(); break; case FLOAT: case DOUBLE: builder.name(columnName).type().unionOf().nullBuilder().endNull().and().doubleType().endUnion().noDefault(); break; Thanks to @Ron Mahoney for finding this issue. ... View more