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  1. MariaDB Server
  2. MDEV-14222

Unnecessary 'cascade' memory allocation for every updated row when there is no FOREIGN KEY

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      MySQL 5.7.2 introduced heap memory allocations for every updated row:

      	if (node->cascade_heap) {
      		 
      		mem_heap_empty(node->cascade_heap);
      		 
      	} else {
      		 
      		node->cascade_heap = mem_heap_create(128);
      		 
      	}
      		 
       
      		 
      	mem_heap_allocator<upd_node_t*> mem_heap_ator(node->cascade_heap);
      		 
       
      		 
      	cascade_upd_nodes = new
      		 
      		(mem_heap_ator.allocate(sizeof(upd_cascade_t)))
      		 
      		upd_cascade_t(deque_mem_heap_t(mem_heap_ator));
      		 
       
      		 
      	new_upd_nodes = new
      		 
      		(mem_heap_ator.allocate(sizeof(upd_cascade_t)))
      		 
      		upd_cascade_t(deque_mem_heap_t(mem_heap_ator));
      		 
       
      		 
      	processed_cascades = new
      		 
      		(mem_heap_ator.allocate(sizeof(upd_cascade_t)))
      		 
      		upd_cascade_t(deque_mem_heap_t(mem_heap_ator));

      If the mem_heap_create(128) was replaced with a larger parameter, then these allocations could reuse the same memory heap for every updated row. It would still be unnecessary to allocate the memory when there are no FOREIGN KEY ON (UPDATE|DELETE) (SET NULL|CASCADE) constraints, but we would avoid the multiple calls to mem_heap_create_block_func() on every updated row.

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          is blocked by

          Bug - A problem which impairs or prevents the functions of the product. MDEV-15219 FOREIGN KEY CASCADE or SET NULL operations will not resume after lock wait

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed
          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. MDEV-15199 Triangular FKs - Cascade delete causes broken referential integrity

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed
          relates to

          Task - A task that needs to be done. MDEV-14958 Merge new release of InnoDB MySQL 5.7.21 to 10.2

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-15611 Due to the failure of foreign key detection, Galera slave node killed himself.

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

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              marko Marko Mäkelä
              marko Marko Mäkelä
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                Updated:
                Resolved:

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