[erlang-questions] Issues with ets:match_delete

[Sverker Eriksson]

The table is 'protected', meaning only the owner <0.1064.0> can write to it.

/Sverker
On fre, 2018-07-13 at 11:05 -0400, Code Wiget wrote:
> Here is a full run of it. I am working on the open source project cqerl:
> 
> (NODE)19> [Test] = ets:match_object(cqerl_clusters, {'_', '_', {Node, '$1'}}).
> [{cluster_table,'$primary_cluster',
>                 {{{192,168,1,104},9042},
>                  [{cassandra_nodes,[{<<"192.168.1.107">>,9042},
>                                     {<<"192.168.1.104">>,9042}]},
>                   {keyspace,devices},
>                   {included_applications,[]},
>                   {reconnect_interval,12}]}}]
> (NODE)20> ets:delete_object(cqerl_clusters, Test).                            
> ** exception error: bad argument
>      in function  ets:delete_object/2
>         called as ets:delete_object(cqerl_clusters,
>                                     {cluster_table,'$primary_cluster',
>                                                    {{{192,168,1,104},9042},
>                                                    
> [{cassandra_nodes,[{<<"192.168.1.107">>,9042},
>                                                                      
>  {<<"192.168.1.104">>,9042}]},
>                                                      {keyspace,devices},
>                                                    
>  {included_applications,[]},
>                                                    
>  {reconnect_interval,12}]}})
> (NODE)21> ets:delete_object(cqerl_clusters, [Test]).
> ** exception error: bad argument
>      in function  ets:delete_object/2
>         called as ets:delete_object(cqerl_clusters,
>                                     [{cluster_table,'$primary_cluster',
>                                                     {{{192,168,1,104},9042},
>                                                    
>  [{cassandra_nodes,[{<<"192.168.1.107">>,9042},
>                                                                        
> {<<"192.168.1.104">>,9042}]},
>                                                       {keyspace,devices},
>                                                      
> {included_applications,[]},
>                                                      
> {reconnect_interval,12}]}}])
> 
> Cant figure why the match is working but not the delete..
> 
> On Jul 13, 2018, 11:01 AM -0400, Code Wiget <codewiget95@REDACTED>, wrote:
> > Here, it seems alive
> > 
> > (NODE13> ets:info(table_name).
> > [{read_concurrency,true},
> >  {write_concurrency,false},
> >  {compressed,false},
> >  {memory,422},
> >  {owner,<0.1064.0>},
> >  {heir,none},
> >  {name,cqerl_clusters},
> >  {size,2},
> >  {node,’NODE'},
> >  {named_table,true},
> >  {type,bag},
> >  {keypos,2},
> >  {protection,protected}]
> > 
> > 
> > On Jul 13, 2018, 7:24 AM -0400, Sverker Eriksson 
> > com>, wrote:
> > > Your ets:match_delete looks fine.
> > > Are you sure the table is still alive? Try ets:info(table_name).
> > > 
> > > When you get an exception in the Erlang shell, the shell process will
> > > terminate and be restarted
> > > losing all process specific resources such as ets tables.
> > > 
> > > 
> > > /Sverker, Erlang/OTP
> > > 
> > > 
> > > On tor, 2018-07-12 at 16:35 -0400, Code Wiget wrote:
> > > > Hey everyone,
> > > > 
> > > > Lets say you have an ets table with entries as shown below:
> > > > 
> > > > {table_name, key, {A, [B]}. 
> > > > 
> > > > I am trying to delete all table entries matching A. I can create a match
> > > > like so:
> > > > 
> > > > ets:match(table_name, {'_', '_', {Node, '$1'}}) 
> > > > 
> > > > and it returns the values for B. But when I run match_delete or
> > > > select_delete, I get a badarg error…:
> > > > 
> > > > ets:match_delete(table_name, {'_', '_', {Node, '$1'}}).
> > > > ** exception error: bad argument
> > > >      in function  ets:select_delete/2
> > > >         called as ets:select_delete(table_name,
> > > >                                    
> > > > [{{'_','_',{{{192,168,1,104},9042},'$1'}},[],[true]}])
> > > >      in call from ets:match_delete/2 (ets.erl, line 726)
> > > > (NODE)16> ets:select_delete(table_name, {'_', '_', {Node, '$1'}}).
> > > > ** exception error: bad argument
> > > >      in function  ets:select_delete/2
> > > >         called as
> > > > ets:select_delete(table_name,{'_','_',{{{192,168,1,104},9042},'$1'}})
> > > > 
> > > > So I tried to match and object and delete it...
> > > > 
> > > > (NODE)17> ets:match_object(table_name, {'_', '_', {Node, '$1'}}). 
> > > > [{table_name,'$primary_cluster',
> > > >                 Info…]
> > > > 
> > > > 
> > > > (NODE)25> ets:delete_object(table_name, Info).                          
> > > >                              
> > > > ** exception error: bad argument
> > > >      in function  ets:delete_object/2
> > > >         called as ets:delete_object(table_name, …. )
> > > > 
> > > > I would like to avoid re-creating the table structure, as it is not from
> > > > a project that I created and would take some time to fix all the code.
> > > > How do I delete something from this table?
> > > > 
> > > > Thanks!
> > > > 
> > > > 
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