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unknown authored
Analysis: The crash is a result of incorrect analysis of whether a secondary key can be extended with a primary in order to compute ORDER BY. The analysis is done in test_if_order_by_key(). This function doesn't take into account that the primary key may in fact index the same columns as the secondary key. For the test query test_if_order_by_key says that there is an extended key with total 2 keyparts. At the same time, the condition if (pkinfo->key_part[i].field->key_start.is_set(nr)) in test_if_cheaper_oredring() becomes true for (i == 0), which results in an invalid access to rec_per_key[-1]. Solution: The best solution would be to reuse KEY::ext_key_parts that is already computed by open_binary_frm(), however after detailed analysis the conclusion is that the change would be too intrusive for a GA release. The solution for 5.5 is to add a guard for the case when the 0-th key part is considered, and to assume that all keys will be scanned in this case.
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