On Fri, Aug 20, 2021 at 1:52 PM alvhe...@alvh.no-ip.org <alvhe...@alvh.no-ip.org> wrote: > Actually, you were right. Hash tables in shared memory can be expanded. > There are some limitations (the hash "directory" is fixed size, which > means the hash table get less efficient if it grows too much), but you > can definitely create more hash entries than the initial size. See for > example element_alloc(), which covers the case of a hash table being > IS_PARTITIONED -- something that only shmem hash tables can be. Note > that ShmemInitHash passes the HASH_ALLOC flag and uses ShmemAllocNoError > as allocation function, which acquires memory from the shared segment.
I realize that the code supports this ... but I thought we had established a policy that only the main lock manager's shared hash tables, and not any others, are actually allowed to make use of this functionality. See commit 7c797e7194d969f974abf579cacf30ffdccdbb95. It seems like a dangerous thing to rely on in any case, since we can't predict how much extra shared memory might actually be available. -- Robert Haas EDB: http://www.enterprisedb.com
