High erlang process memory executing mnesia:dirty_select/2 - erlang

Question

I have an mnesia table gen_saga_persist which is queried by a process every 1 second.
The function used is mnesia:dirty_select(gen_saga_persist, [{#gen_saga_persist{id = '$1', app = undefined, partition = 33, execution_type = auto, _ = '_'}, [], ['$1']}])
Now as the table grows, i observed my process querying this table grows in terms of memory. Can anyone help me understand why my process memory is increasing (mnesia newbie here), as i am not even storing the result in my process data or anywhere.
Mnesia table info:
[{access_mode,read_write},
{active_replicas,[server#localhost]},
{all_nodes,[server#localhost]},
{arity,12},
{attributes,[id,partition,app,type,subtype,name,status,
execution_type,retry_count,update_time,controller_state]},
{checkpoints,[]},
{commit_work,[{index,ordered_set,
[{{9,ordered},{ram,#Ref<0.3472765205.1199964162.76896>}},
{{8,ordered},{ram,#Ref<0.3472765205.1199964162.76882>}},
{{7,ordered},{ram,#Ref<0.3472765205.1199964163.74776>}},
{{6,ordered},{ram,#Ref<0.3472765205.1199964162.76856>}},
{{5,ordered},{ram,#Ref<0.3472765205.1199964161.79429>}},
{{4,ordered},{ram,#Ref<0.3472765205.1199964161.79409>}},
{{3,ordered},{ram,#Ref<0.3472765205.1199964162.76810>}}]}]},
{cookie,{{1632211298276938000,-576460752303418559,1},
server#localhost}},
{cstruct,{cstruct,gen_saga_persist,ordered_set,[],
[server#localhost],
[],[],0,read_write,false,
[{3,ordered},
{4,ordered},
{5,ordered},
{6,ordered},
{7,ordered},
{8,ordered},
{9,ordered}],
[],false,gen_saga_persist,
[id,partition,app,type,subtype,name,status,execution_type,
retry_count,update_time,controller_state],
[],[],[],
{{1632211298276938000,-576460752303418559,1},
server#localhost},
{{2,0},[]}}},
{disc_copies,[server#localhost]},
{disc_only_copies,[]},
{external_copies,[]},
{frag_properties,[]},
{index,[9,8,7,6,5,4,3]},
{index_info,{index,ordered_set,
[{{9,ordered},{ram,#Ref<0.3472765205.1199964162.76896>}},
{{8,ordered},{ram,#Ref<0.3472765205.1199964162.76882>}},
{{7,ordered},{ram,#Ref<0.3472765205.1199964163.74776>}},
{{6,ordered},{ram,#Ref<0.3472765205.1199964162.76856>}},
{{5,ordered},{ram,#Ref<0.3472765205.1199964161.79429>}},
{{4,ordered},{ram,#Ref<0.3472765205.1199964161.79409>}},
{{3,ordered},{ram,#Ref<0.3472765205.1199964162.76810>}}]}},
{load_by_force,false},
{load_node,server#localhost},
{load_order,0},
{load_reason,local_only},
{local_content,false},
{majority,false},
{master_nodes,[]},
{memory,2455944},
{ram_copies,[]},
{record_name,gen_saga_persist},
{record_validation,{gen_saga_persist,12,ordered_set}},
{size,7747},
{snmp,[]},
{storage_properties,[]},
{storage_type,disc_copies},
{subscribers,[]},
{type,ordered_set},
{user_properties,[]},
{version,{{2,0},[]}},
{where_to_commit,[{server#localhost,disc_copies}]},
{where_to_read,server#localhost},
{where_to_wlock,{[server#localhost],false}},
{where_to_write,[server#localhost]},
{wild_pattern,#gen_saga_persist{id = '_',partition = '_',
app = '_',type = '_',subtype = '_',name = '_',status = '_',
execution_type = '_',retry_count = '_',update_time = '_',
controller_state = '_'}},
{{index,3},#Ref<0.3472765205.1199964162.76810>},
{{index,4},#Ref<0.3472765205.1199964161.79409>},
{{index,5},#Ref<0.3472765205.1199964161.79429>},
{{index,6},#Ref<0.3472765205.1199964162.76856>},
{{index,7},#Ref<0.3472765205.1199964163.74776>},
{{index,8},#Ref<0.3472765205.1199964162.76882>},
{{index,9},#Ref<0.3472765205.1199964162.76896>}]
Process info:
[{current_function,{timer,sleep,1}},
{initial_call,{bin_updates_dispatcher,poll_func,3}},
{status,waiting},
{message_queue_len,0},
{links,[]},
{dictionary,[]},
{trap_exit,false},
{error_handler,error_handler},
{priority,normal},
{group_leader,<105603.71.0>},
{total_heap_size,4781410},
{heap_size,1199557},
{stack_size,6},
{reductions,155758726},
{garbage_collection,[{max_heap_size,#{error_logger => true,kill => true,size => 0}},
{min_bin_vheap_size,46422},
{min_heap_size,233},
{fullsweep_after,65535},
{minor_gcs,11}]},
{suspending,[]}]
Process function:
poll_gen_saga_persist_table(Delay) ->
Pid = spawn(bin_updates_dispatcher, poll_func, [Delay, gen_saga_persist,
[{#gen_saga_persist{
id = '$1', app = undefined, partition = 33, execution_type = auto, _ = '_'
}, [], ['$1']}]]),
unlink(Pid),
Pid.
poll_func(Delay, TableName, [{MatchSpec, Guards, Return}]) ->
mnesia:dirty_select(TableName, [{MatchSpec, Guards, Return}]),
timer:sleep(Delay),
poll_func(Delay, TableName, [{MatchSpec, Guards, Return}]).

Answer 1

I think it is not related with mneisa, it's caused by your poll_func. It's running forever in the self-loop.
poll_func(Delay, TableName, [{MatchSpec, Guards, Return}]) ->
mnesia:dirty_select(TableName, [{MatchSpec, Guards, Return}]),
timer:sleep(Delay),
poll_func(Delay, TableName, [{MatchSpec, Guards, Return}]). <--- it can't release any memory.
You can rewrite the following code by gen_server by using timer:send_after message
Pid = spawn(bin_updates_dispatcher, poll_func, [Delay, gen_saga_persist,
[{#gen_saga_persist{
id = '$1', app = undefined, partition = 33, execution_type = auto, _ = '_'
}, [], ['$1']}]]),
and simplifize poll_func
poll_func(Delay, TableName, [{MatchSpec, Guards, Return}]) ->
mnesia:dirty_select(TableName, [{MatchSpec, Guards, Return}]).
Therefore for the pid, the memory caused by dirty_select will be released after completing the calling, and be reused in the next loop.

Answer 2

You need to add a stop condition for this function:
poll_func(Delay, TableName, [{MatchSpec, Guards, Return}]) ->
mnesia:dirty_select(TableName, [{MatchSpec, Guards, Return}]),
timer:sleep(Delay),
poll_func(Delay, TableName, [{MatchSpec, Guards, Return}]).
Because you are calling poll_func function one more time and it will go to loop forever without a stop condition.