Paul Rogers created IMPALA-7881:
-----------------------------------
Summary: Visualize AST for easier debugging
Key: IMPALA-7881
URL: https://issues.apache.org/jira/browse/IMPALA-7881
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Affects Versions: Impala 3.0
Reporter: Paul Rogers
Assignee: Paul Rogers
The parser creates a "raw" AST (abstract syntax tree), which is then
"decorated" by the analyzer. Often, when debugging the analyzer, one wants to
see the state of the tree. At present, doing so using an IDE's debugger is
tedious as one has to slowly navigate within the tree.
Provide a debug tool that visualizes the tree. For example:
{noformat}
<root> (SelectStmt): {
. isExplain: false
. analyzer: <Skip Analyzer>
. withClause: <null>
. orderByElements: [
. . 0 (OrderByElement): {
. . . expr (SlotRef): {
...
. selectList (SelectList): {
. . planHints: []
. . isDistinct: false
. . items: [
. . . 0 (SelectListItem): {
. . . . expr (SlotRef): {
...
. . . . . rawPath: [
. . . . . . 0: "id"
. . . . . ]
. . . . . label: "id"
{noformat}
Many improvements can be made. (Format as JSON, export to a nice JSON
visualizer, etc.) The purpose here is to just get started.
To avoid the need to write code for every AST node class (of which there are
many), use Java introspection to walk fields directly. The result may be overly
verbose, but it is a quick way to get started.
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