Re: Hash tables in dynamic shared memory

On Wed, Oct 5, 2016 at 3:10 AM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> Here is an experimental hash table implementation that uses DSA memory
> so that hash tables can be shared by multiple backends and yet grow
> dynamically. Development name: "DHT".

+dht_iterate_begin(dht_hash_table *hash_table,
+ dht_iterator *iterator,
+ bool exclusive)
+{
+ Assert(hash_table->control->magic == DHT_MAGIC);
+
+ iterator->hash_table = hash_table;
+ iterator->exclusive = exclusive;
+ iterator->partition = 0;
+ iterator->bucket = 0;
+ iterator->item = NULL;
+ iterator->locked = false;

While reviewing , I found that in dht_iterate_begin function, we are
not initializing
iterator->last_item_pointer to InvalidDsaPointer;
and during scan this variable will be used in advance_iterator
function. (I think this will create problem, even loss of some tuple
?)

+advance_iterator(dht_iterator *iterator, dsa_pointer bucket_head,
+ dsa_pointer *next)
+{
+ dht_hash_table_item *item;
+
+ while (DsaPointerIsValid(bucket_head))
+ {
+ item = dsa_get_address(iterator->hash_table->area,
+ bucket_head);
+ if ((!DsaPointerIsValid(iterator->last_item_pointer) ||
+ bucket_head < iterator->last_item_pointer) &&

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com