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https://issues.apache.org/jira/browse/DRILL-2077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14297327#comment-14297327
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Chris Westin commented on DRILL-2077:
-------------------------------------
This should go in the new markdown pages in git.
> Provide a clear starting point for new developers about what to start reading
> to learn about Drill
> --------------------------------------------------------------------------------------------------
>
> Key: DRILL-2077
> URL: https://issues.apache.org/jira/browse/DRILL-2077
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Jason Altekruse
> Assignee: Jason Altekruse
>
> As part of my package level javadocs posted in DRILL-1904 I tried to document
> the root org.apache.drill.exec package. We should have some good information
> here as well as in the markdown file on the git repo about the best place to
> start reading the code to understand how drill operates.
> Here is a description I started. I think we want to make sure this is
> informative but concise. I want to get in the rest of the package docs, so I
> am leaving this here as a TODO, please feel free to comment, revise or add to
> this.
> {code}
> * A good place to start learning about Drill is exploring the query plans. A
> * Drill physical plan is defined as a connected graph of operators that read
> * and manipulate data. Operators are configured by implementations of the
> {@See
> * PhysicalOperator} interface. These query graphs are translated into a graph
> * of physical operators that will actually process data at query execution
> * time. The connections between these nodes are materialized as interfaces
> * where data is passed between different operators. As Drill is distributed
> * these connections can take the form of an RPC layer between the nodes in a
> * Drill cluster.
> *
> * While physical plans can be written by hand, the primary interface for
> Drill
> * is SQL. Drill is targeted for compliance with the ANSI SQL 2003
> * specification. Query parsing and optimization is handled by Calcite, an
> * Apache incubator project, also used for planning in Apache Hive. Drill
> * defines many planning rules an optimizations that plug into the Calcite
> * planning engine to generate optimal plans for the Drill engine.
> *
> * Unlike most query systems, Drill is designed to query raw files without
> * a predefined catalog of metadata defining the types of data or columns
> * available in the dataset. To maintain performance in a flexible schema
> * environment, Drill uses runtime code generation to compile custom java
> * code as operators receive a message of change in schema.
> {code}
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