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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (NIFI-2881) Allow Database Fetch processor(s) to accept incoming flow files and use Expression Language
Date Thu, 02 Feb 2017 11:51:51 GMT


ASF GitHub Bot commented on NIFI-2881:

Github user ijokarumawak commented on a diff in the pull request:
    --- Diff: nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/
    @@ -212,9 +215,21 @@ public void onTrigger(final ProcessContext context, final ProcessSessionFactory
             final Map<String, String> statePropertyMap = new HashMap<>(stateMap.toMap());
             //If an initial max value for column(s) has been specified using properties,
and this column is not in the state manager, sync them to the state property map
    -        for(final Map.Entry<String,String> maxProp : maxValueProperties.entrySet()){
    -            if (!statePropertyMap.containsKey(maxProp.getKey().toLowerCase())) {
    -                statePropertyMap.put(maxProp.getKey().toLowerCase(), maxProp.getValue());
    +        for (final Map.Entry<String, String> maxProp : maxValueProperties.entrySet())
    +            String maxPropKey = maxProp.getKey().toLowerCase();
    +            String fullyQualifiedMaxPropKey = getStateKey(tableName, maxPropKey);
    +            if (!statePropertyMap.containsKey(fullyQualifiedMaxPropKey)) {
    +                String newMaxPropValue;
    +                // If we can't find the value at the fully-qualified key name, it is
possible (under a previous scheme)
    +                // the value has been stored under a key that is only the column name.
Fall back to check the column name,
    +                // but store the new initial max value under the fully-qualified key.
    +                if (statePropertyMap.containsKey(maxPropKey)) {
    +                    newMaxPropValue = statePropertyMap.get(maxPropKey);
    +                } else {
    +                    newMaxPropValue = maxProp.getValue();
    --- End diff --
    Thanks for updating the docs, it became clearer :)

> Allow Database Fetch processor(s) to accept incoming flow files and use Expression Language
> -------------------------------------------------------------------------------------------
>                 Key: NIFI-2881
>                 URL:
>             Project: Apache NiFi
>          Issue Type: Improvement
>          Components: Extensions
>            Reporter: Matt Burgess
>            Assignee: Matt Burgess
> The QueryDatabaseTable and GenerateTableFetch processors do not allow Expression Language
to be used in the properties, mainly because they also do not allow incoming connections.
This means if the user desires to fetch from multiple tables, they currently need one instance
of the processor for each table, and those table names must be hard-coded.
> To support the same capabilities for multiple tables and more flexible configuration
via Expression Language, these processors should have properties that accept Expression Language,
and GenerateTableFetch should accept (optional) incoming connections.
> Conversation about the behavior of the processors is welcomed and encouraged. For example,
if an incoming flow file is available, do we also still run the incremental fetch logic for
tables that aren't specified by this flow file, or do we just do incremental fetching when
the processor is scheduled but there is no incoming flow file. The latter implies a denial-of-service
could take place, by flooding the processor with flow files and not letting it do its original
job of querying the table, keeping track of maximum values, etc.
> This is likely a breaking change to the processors because of how state management is
implemented. Currently since the table name is hard coded, only the column name comprises
the key in the state. This would have to be extended to have a compound key that represents
table name, max-value column name, etc.

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