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c37016b0e5
tmp_memory_table_size is limiting the size of internal temporary memory tables. max_heap_table_size is there to limiting the size of explictely created memory tables. max_heap_table_size can be much larger than tmp_memory_table_size as the memory used by temporary tables is in the control of the user. This commit changes the usage of max_heap_table_size for internal buffers to min(max_heap_table_size, tmp_memory_table_size), like we do for internal temporary tables. This changes the in memory buffer allocations for: - GROUP_CONCAT() - Calculating the cost for scanning memory tables (the original code was wrong here as it used the wrong size for memory tables). - ANALYZE TABLE buffer sizes for calculating distinct column values Other things: - Add THD::ram_limitation() to provide consistent memory limitations in all code that used variables.tmp_memory_table_size as buffers. If tmp_memory_table_size == 0, then 8192 is used. This replaces Item_sum::ram_limitation which used 1024 as min buffer, which is way to little for any practical case. - Added security guard in heap_prepare_hp_create_info to ensure that max_table_size is calculated same way as in MariaDB server. - Fixed initial memory allocations for Item_func_group::concat which allocated 'max allowed memory' at start. Now it allocates only 1/16 of that memory at start.