Hi David, Your b.json file has only nulls; there is no way for Drill to determine what type of null is in your file. Drill requires each NULL to be a null of some type. Often, Drill guesses nullable int, which is why you saw the problem in your query.
If all your fields are strings, there is a workaround: use the "all-text-mode" when reading your JSON file. [1] Another workaround is to design the files so that the first record always has a non-null value for every field so Drill can guess the type correctly. If any fields contain other types, you can use all text mode, then cast the non-text fields from text to the proper type. This is a known limitation: not just with Drill, but with any schema-free system. See DRILL-6035 [2]. At the present type, Drill supports no type of schema to help resolve this kind of ambiguity. (Though, having one would be the ideal solution to this kind of problem.) Thanks, - Paul [1] https://drill.apache.org/docs/json-data-model/ [2] https://issues.apache.org/jira/browse/DRILL-6035 On Friday, February 23, 2018, 12:04:01 PM PST, Lee, David <[email protected]> wrote: Using Drill's CTAS statements I've run into a schema inconsistency issue and I'm not sure how to solve it.. CREATE TABLE name [ (column list) ] AS query; If I have a directory called Cities which have JSON files which look like: a.json: { "city":"San Francisco", "zip":"94105"} { "city":"San Jose", "zip":"94088"} b.json: { "city":"Toronto ", "zip": null} { "city":"Montreal", "zip" null} If I create a parquet file out of the Cities directory I will end up with files called: 1_0_0.parquet through 1_5_1.parquet Now I got a problem: Most of the parquet files have a column type of char for zip. Some of the parquet files have a column type of int for zip because the zip value for a group of records was NULL.. This produces schema change errors later when trying to query the parquet directory. Is it possible for Drill to do a better job learning schemas across all json files in a directory before creating parquet? This message may contain information that is confidential or privileged. If you are not the intended recipient, please advise the sender immediately and delete this message. See http://www.blackrock.com/corporate/en-us/compliance/email-disclaimers for further information. Please refer to http://www.blackrock.com/corporate/en-us/compliance/privacy-policy for more information about BlackRock’s Privacy Policy. For a list of BlackRock's office addresses worldwide, see http://www.blackrock.com/corporate/en-us/about-us/contacts-locations. © 2018 BlackRock, Inc. All rights reserved.
