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Create flex table from existing table or accessing JSON in non-flex table
I have tables I'm importing from another database which have JSON a few encoded fields . Is there a way to create a flex table based on a column of an existing table or a way to parse the contents of a single cell?
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Comments
If you have access to Vertica 7.1, take a look at the new function "MapJSONExtractor()":
http://my.vertica.com/docs/7.1.x/PDF/HP_Vertica_7.1.x_Flex_Tables.pdf
(See page 70.) This function parses a JSON string into a Vertica map structure, which is what Flex uses internally.
Does that help?
Adam
mapjsonextractor works fine, for single objects.
However if i create a table "jsondata" with a single varchar column called "json" and add 2 rows with the following data:
[{"el":1,"k1":"v1","k2":"v2"}]
[{"el":2,"k1":"v1","k2":"v2"},{"el":3,"k1":"v1","k2":"v2"}]
=> select maptostring(mapjsonextractor(json)) from jsondata;
WARNING 3224: Error in calling destroy() for User Defined Scalar Function MapJSONExtractor at [src/JSONParser.cpp:902], error code: 0, message: Rejecting row [4].
maptostring
----------------------------------------------------
{
"el" : "1",
"k1" : "v1",
"k2" : "v2"
}
(2 rows)
If i load the same data into a flex table it does work properly, however i do not know of a way that i can query a varchar column with json data of an existing table (which is what i have to work with) and insert it into a flex table.
Any suggestions on how to properly work with data like this?
Hi!
>> Error in calling destroy() for User Defined Scalar
Types of UDxs
[...]
Means that UDSF returns one row per one value and your single value contains 2 rows:
>> Any suggestions on how to properly work with data like this?
Split data: single VARCHAR = single JSON row.
That explains things.
From the documentation however i was under the impression that this would be a UDTF:
"Extracts content of repeated JSON data objects, including nested maps, or data with an outer list of JSON elements."
Cheers,
Dennis