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https://issues.apache.org/jira/browse/HIVE-10190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14486058#comment-14486058
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Pengcheng Xiong commented on HIVE-10190:
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I would prefer a BFS rather than a DFS. And I think it will solve the problem.
If it is still an issue, i can try to solve it in the parser level.
> CBO: AST mode checks for TABLESAMPLE with
> AST.toString().contains("TOK_TABLESPLITSAMPLE")
> -----------------------------------------------------------------------------------------
>
> Key: HIVE-10190
> URL: https://issues.apache.org/jira/browse/HIVE-10190
> Project: Hive
> Issue Type: Bug
> Components: CBO
> Affects Versions: 1.2.0
> Reporter: Gopal V
> Assignee: Pengcheng Xiong
> Priority: Trivial
> Labels: perfomance
>
> {code}
> public static boolean validateASTForUnsupportedTokens(ASTNode ast) {
> String astTree = ast.toStringTree();
> // if any of following tokens are present in AST, bail out
> String[] tokens = { "TOK_CHARSETLITERAL", "TOK_TABLESPLITSAMPLE" };
> for (String token : tokens) {
> if (astTree.contains(token)) {
> return false;
> }
> }
> return true;
> }
> {code}
> This is an issue for a SQL query which is bigger in AST form than in text
> (~700kb).
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