"Run SQL query only during execute, skips confiugre" option

genericknimenodes
#1

Hello guys,

I’m in middle of something envolving the node “Database Reader”, in this node we have the “Run SQL query only during execute, skips configure” option, but I dont understand what the Node Description says about it, maybe because I’m new at ETL Development and Knime.

Could yoy guys please elaborate it?

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#2

Hi,
to figure out what data will be returned by the database (column names and types, basically), KNIME can execute the query with a limit 1 suffix after configuration. This is so that the following nodes know what to expect, so that you can, for example, configure a following column filter node before actually executing the Database Reader. Disabling the option requires you to execute it before configuring other nodes that depend on its output. Does that make sense?
Kind regards
Alexander

Edit:
A KNIME node has two important functions: configure and execute. In the configure step the node calculates what it will output and in the execute it will actually produce the output. Configure is called when the node receives or loses input connections or when the settings change. Subsequently the following nodes are also configured, i.e. notified about possible changes in the input. As mentioned above, this makes it easier to configure nodes without actual data being present.

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#3

Hi there @wpardim7,

considering you are just starting with ETL development and KNIME I suggest you start with newest KNIME Database Extension nodes which are production ready from KNIME version 4.0.0. Database Reader you are currently using is from legacy Database Extension.

Here is link to the Database documentation that can help you in your ETL development:
https://docs.knime.com/?category=extensions&release=2019-06

Exploring KNIME Hub for workflow examples and nodes can be pretty useful as well.

To get the newest KNIME version go here.

If any questions/comments feel free to ask.

Br,
Ivan

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#4

Hi @AlexanderFillbrunn
That makes sense, I though this option would make the query start before the other nodes.

Thanks.

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closed #5

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