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ASF GitHub Bot commented on DRILL-7278: --------------------------------------- arina-ielchiieva commented on pull request #1797: DRILL-7278: Refactor result set loader projection mechanism URL: https://github.com/apache/drill/pull/1797#discussion_r289936396 ########## File path: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/scan/project/package-info.java ########## @@ -71,9 +141,72 @@ * distinct class. Classes combine via composition to create a "framework" * suitable for each kind of reader: whether it be early or late schema, * file-based or something else, etc. + * + * <h4>Nuances of Reader-Level Projection</h4> + * + * We've said that the scan-level projection identifies what the query + * <i>wants</i>. We've said that the reader identifies what the external + * data actually <i>is</i>. We've mentioned how we bridge between the + * two. Here we explore this in more detail. + * <p> + * Run-time schema resolution occurs at various stages: * <p> + * <ul> + * <li>The per-column resolution identified earlier: matching types, + * type conversion, and so on.</li> + * <li>The reader will provides some set of columns. We don't know which Review comment: ```suggestion * <li>The reader will provide some set of columns. We don't know which ``` ---------------------------------------------------------------- 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: us...@infra.apache.org > Refactor result set loader projection mechanism > ----------------------------------------------- > > Key: DRILL-7278 > URL: https://issues.apache.org/jira/browse/DRILL-7278 > Project: Apache Drill > Issue Type: Improvement > Affects Versions: 1.16.0 > Reporter: Paul Rogers > Assignee: Paul Rogers > Priority: Major > Fix For: 1.17.0 > > -- This message was sent by Atlassian JIRA (v7.6.3#76005)