Cursor::index_read_idx_map() violates blobs memory rules

[Stewart Smith]

nt Cursor::index_read_idx_map(unsigned char * buf, uint32_t index,
                                const unsigned char * key,
                                key_part_map keypart_map,
                                enum ha_rkey_function find_flag)
{
  int error, error1;
  error= doStartIndexScan(index, 0);
  if (!error)
  {
    error= index_read_map(buf, key, keypart_map, find_flag);
    error1= doEndIndexScan();
  }
  return error ? error : error1;
}

The doEndIndexScan() call tells the Engine that it can free the BLOB records.

this query from type_blob.test can show this (when run with an appropriate engine):

select replace(t3._field_140, "\r","^M"),t3_id,min(t3._field_131), min(t3._field_135), min(t3._field_139), min(t3._field_137), min(link_alias_142._field_165), min(link_alias_133._field_72), min(t3._field_145), min(link_alias_148._field_156), replace(min(t3._field_140), "\r","^M"),t3.t3_id from t3 left join t4 on t4.seq_0_id = t3.t3_id left join t7 link_alias_142 on t4.seq_1_id = link_alias_142.t7_id left join t6 on t6.seq_0_id = t3.t3_id left join t1 link_alias_133 on t6.seq_1_id = link_alias_133.t1_id left join t2 on t2.seq_0_id = t3.t3_id left join t5 link_alias_148 on t2.seq_1_id = link_alias_148.t5_id where t3.t3_id in (1) group by t3.t3_id order by link_alias_142._field_166, _field_139, link_alias_133._field_72, _field_135, link_alias_148._field_156;

[Stewart Smith (stewart)]

I don't have a good solution to this yet. Spent a while looking, but the best way is to go for a more complete and better set of blob memory management rules, which is beyond the scope of this week at least.