Hi! To compile a statement a lot of Nodes are allocated and they are rarely freed during compilation.
Most of them lives until the statement is destroyed. With each node there is the memory manager overhead (16 bytes in release build), that exists there to make individual node deallocation possible. A waste of space in this case, as nodes are de-allocated as a whole with the pool. I did some tests to see how many nodes were created and how much memory a statement pool uses: -- 39 nodes, 31728 bytes allocated select * from rdb$database; -- 109 nodes, 91904 bytes allocated select * from rdb$database union all select * from rdb$database union all select * from rdb$database union all select * from rdb$database union all select * from rdb$database; -- 163 nodes, 120496 bytes allocated execute block as declare n integer; begin select rdb$relation_id from rdb$database into n; -- select repeated 20 more times end! So multiplying number of nodes by 16 we have around 2% of waste in these tests. I'm thinking on using something like a memory arena so a large block is allocated (from the pool) and nodes allocation uses the arena, not needing a per-node overhead. It's not necessary to have a single large block. Many could be created and we start with not very large to not waste space for small statements. We could also estimate initial block size from the BLR size. And inserting a protected delete operator in Node we avoid them being explicitly called (with will crash). What do you think? Adriano Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
