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HIVE-29632: hive.fetch.task.caching=true causes unbounded heap allocation thus crashing HiveServer2 with OutOfMemoryError #6510

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HIVE-29632: hive.fetch.task.caching=true causes unbounded heap allocation thus crashing HiveServer2 with OutOfMemoryError #6510

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4 changes: 3 additions & 1 deletion cli/src/java/org/apache/hadoop/hive/cli/CliDriver.java
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Original file line number Diff line number Diff line change
Expand Up @@ -295,7 +295,9 @@ CommandProcessorResponse processLocalCmd(String cmd, CommandProcessor proc, CliS
console.printError("Failed with exception " + e.getClass().getName() + ":" + e.getMessage(),
"\n" + org.apache.hadoop.util.StringUtils.stringifyException(e));
throw new CommandProcessorException(1);
} finally {
} catch (RuntimeException e) {
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@vikramahuja1001 vikramahuja1001 Jun 2, 2026

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Reason for this change:

  1. The SimpleFetchOptimizer change disables caching for non-ACID tables, making FetchTask.execute() a no op. Rows are now fetched lazily via Driver.getResults() after qp.run(). So the exceptions that previously surfaced inside qp.run() now escapes as unchecked RunTimeException from the fetch loop.
  2. ProcessLocalCmd() only caught IOExceptions, so the RunTImeException bubbled up and never became a CommandProcessorException causing tests tests like, udf_assert_true.q, udf_assert_true2.q to fail.
  3. The fix adds a separate catch (RuntimeException e) that silently converts it to CommandProcessorException. It intentionally does not reprint the error since FetchTask.executeInner() already did that. Plus doing that will change .q.out file which i was trying to avoid.

throw new CommandProcessorException(1);
} finally {
qp.close();
ShimLoader.getHadoopShims()
.setHadoopSessionContext(String.format(USER_ID, ss.getSessionId(), ss.getUserName()));
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11 changes: 9 additions & 2 deletions ql/src/java/org/apache/hadoop/hive/ql/optimizer/SimpleFetchOptimizer.java
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Expand Up @@ -60,6 +60,7 @@
import org.apache.hadoop.hive.ql.exec.TaskFactory;
import org.apache.hadoop.hive.ql.exec.Utilities;
import org.apache.hadoop.hive.ql.hooks.ReadEntity;
import org.apache.hadoop.hive.ql.io.AcidUtils;
import org.apache.hadoop.hive.ql.io.ContentSummaryInputFormat;
import org.apache.hadoop.hive.ql.io.HiveInputFormat;
import org.apache.hadoop.hive.ql.metadata.HiveException;
Expand Down Expand Up @@ -144,8 +145,14 @@ private FetchTask optimize(ParseContext pctx, String alias, TableScanOperator so
if (fetch != null && checkThreshold(fetch, limit, pctx)) {
FetchWork fetchWork = fetch.convertToWork();
FetchTask fetchTask = (FetchTask) TaskFactory.get(fetchWork);
fetchTask.setCachingEnabled(HiveConf.getBoolVar(pctx.getConf(),
HiveConf.ConfVars.HIVE_FETCH_TASK_CACHING));
boolean cachingEnabled = HiveConf.getBoolVar(pctx.getConf(),
HiveConf.ConfVars.HIVE_FETCH_TASK_CACHING);
if (cachingEnabled && !AcidUtils.isTransactionalTable(fetch.table)) {
LOG.debug("Fetch task caching is enabled but table {} is not transactional. " +
"Caching is only supported for ACID tables. Disabling.", fetch.table.getCompleteName());
cachingEnabled = false;
}
fetchTask.setCachingEnabled(cachingEnabled);
fetchWork.setSink(fetch.completed(pctx, fetchWork));
fetchWork.setSource(source);
fetchWork.setLimit(limit);
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