paul-rogers commented on a change in pull request #2030: Update docs for Metastore to point that all format plugins are supported URL: https://github.com/apache/drill/pull/2030#discussion_r394567289
########## File path: _docs/sql-reference/sql-commands/021-create-schema.md ########## @@ -209,13 +210,15 @@ Values are trimmed when converting to any type, except for varchar. ## Usage Notes -### General Information -- Schema provisioning only works with tables defined as directories because Drill must have a place to store the schema file. The directory can contain one or more files. +### General Information +- Schema provisioning using schema file works only with tables defined as directories because Drill must have a place to store the schema file. The directory can contain one or more files. - Text files must have headers. The default extension for delimited text files with headers is `.csvh`. Note that the column names that appear in the headers match column definitions in the schema. - You do not have to enumerate all columns in a file when creating a schema. You can indicate the columns of interest only. - Columns in the defined schema do not have to be in the same order as in the data file. - Column names must match. The case can differ, for example “name” and “NAME” are acceptable. -- Queries on columns with data types that cannot be converted fail with a `DATA_READ_ERROR`. +- Queries on columns with data types that cannot be converted fail with a `DATA_READ_ERROR`. Review comment: Drill is unique in that it infers table schema at runtime. However, sometimes schema inference can fail when Drill cannot infer the correct types. For example, Drill treats all fields in a text file as text. Drill may not be able to determine the type of fields in JSON files if the fields are missing or set to `null` in the first few records in the file. Drill issues a `DATA_READ_ERROR` when runtime schema inference fails. When Drill cannot correctly infer the schema, you can instead use your knowledge of the file layout to tell Drill the proper schema to use. Schema provisioning is the feature you use to specify the schema. You can provide a schema for the file as a whole using the `CREATE OR REPLACE SCHEMA` command ((insert link)) or for a single query using a table function ((insert link)). Please see ... for details. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
