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https://issues.apache.org/jira/browse/IMPALA-8151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16759528#comment-16759528
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Tim Armstrong commented on IMPALA-8151:
---------------------------------------
Yeah it would make sense. Overhead isn't an issue if you mean runtime overhead
- sizeof() is evaluated at compile time.
> HiveUdfCall assumes StringValue is 16 bytes
> -------------------------------------------
>
> Key: IMPALA-8151
> URL: https://issues.apache.org/jira/browse/IMPALA-8151
> Project: IMPALA
> Issue Type: Bug
> Components: Backend
> Affects Versions: Impala 3.2.0
> Reporter: Tim Armstrong
> Assignee: Pooja Nilangekar
> Priority: Blocker
> Labels: crash
>
> HiveUdfCall has the sizes of internal types hardcoded as magic numbers:
> {code}
> switch (GetChild(i)->type().type) {
> case TYPE_BOOLEAN:
> case TYPE_TINYINT:
> // Using explicit sizes helps the compiler unroll memcpy
> memcpy(input_ptr, v, 1);
> break;
> case TYPE_SMALLINT:
> memcpy(input_ptr, v, 2);
> break;
> case TYPE_INT:
> case TYPE_FLOAT:
> memcpy(input_ptr, v, 4);
> break;
> case TYPE_BIGINT:
> case TYPE_DOUBLE:
> memcpy(input_ptr, v, 8);
> break;
> case TYPE_TIMESTAMP:
> case TYPE_STRING:
> case TYPE_VARCHAR:
> memcpy(input_ptr, v, 16);
> break;
> default:
> DCHECK(false) << "NYI";
> }
> {code}
> STRING and VARCHAR were only 16 bytes because of padding. This padding is
> removed by IMPALA-7367, so this will read past the end of the actual value.
> This could in theory lead to a crash.
> We need to change the value, but we should probably also switch to
> sizeof(StringValue) so that it doesn't get broken by similar changes in
> future.
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