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Many lookup types are available. What is the guide for choosing one or another?

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  • Arun
    I am installing my Postfix server. I am reading about the configuration options. I see that there are many formats to use for lookups. I see for exanple this
    Message 1 of 10 , Jul 11, 2014
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      I am installing my Postfix server.

      I am reading about the configuration options.

      I see that there are many formats to use for lookups.

      I see for exanple this

      ...
      smtpd_tls_session_cache_database = btree:/var/lib/postfix/smtpd_scache
      smtp_tls_session_cache_database = btree:/var/lib/postfix/smtp_scache

      alias_maps = hash:/etc/aliases
      ...

      in one example doc.

      I can understand that there ARE diferences.  I do not understand when to use which one.

      For example I have heard about the LMDB format from the OpenLDAP project.  I hear that it is fast and lightweight and some persons say one of the best options.

      So is it best or even ok to do this?

      ...
      smtpd_tls_session_cache_database = lmdb:/var/lib/postfix/smtpd_scache
      smtp_tls_session_cache_database = lmdb:/var/lib/postfix/smtp_scache

      alias_maps = lmdb:/etc/aliases
      ...

      I am just wanting to know when to use which type?

      Arun
    • Wietse Venema
      ... In that case, I suggest that you use what is shown the examples. Every type (hash, btree, lmdb, and so on) presents a compromise between different
      Message 2 of 10 , Jul 11, 2014
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        Arun:
        >I see that there are many formats to use for lookups.
        >
        >I see for exanple this
        >
        >...
        >
        >smtpd_tls_session_cache_database = btree:/var/lib/postfix/smtpd_scache
        >smtp_tls_session_cache_database = btree:/var/lib/postfix/smtp_scache
        >
        >alias_maps = hash:/etc/aliases
        >
        >...
        >
        >in one example doc.
        >
        >I can understand that there ARE diferences. I do not understand
        >when to use which one.

        In that case, I suggest that you use what is shown the examples.
        Every type (hash, btree, lmdb, and so on) presents a compromise
        between different requirements.

        If you're looking for a guide, use the Postfix documentation.

        Wietse
      • Arun
        ... I did use the Postfix documentation. Is it wrong to ask questions?  Is why not allowable ? I guess it is because you say so! I have reading the mailing
        Message 3 of 10 , Jul 11, 2014
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          > I suggest that you use what is shown the examples.

          I did use the Postfix documentation.

          Is it wrong to ask questions?  Is 'why' not allowable ? I guess it is because you say so!

          I have reading the mailing lists too and see you are the author.  Why are you always being such a mean old man to new people?  You do this a lot.




          On Friday, July 11, 2014 6:04 PM, Wietse Venema <wietse@...> wrote:


          Arun:

          >I see that there are many formats to use for lookups.
          >
          >I see for exanple this
          >
          >...
          >
          >smtpd_tls_session_cache_database = btree:/var/lib/postfix/smtpd_scache
          >smtp_tls_session_cache_database = btree:/var/lib/postfix/smtp_scache
          >
          >alias_maps = hash:/etc/aliases
          >
          >...
          >
          >in one example doc.
          >
          >I can understand that there ARE diferences. I do not understand
          >when to use which one.


          In that case, I suggest that you use what is shown the examples.
          Every type (hash, btree, lmdb, and so on) presents a compromise
          between different requirements.

          If you're looking for a guide, use the Postfix documentation.

              Wietse



        • Viktor Dukhovni
          ... It is conjectured that btree is perhaps better for random-access read-write databases where Postfix maintains an update cursor for cleanup of stale
          Message 4 of 10 , Jul 11, 2014
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            On Fri, Jul 11, 2014 at 05:45:30PM -0700, Arun wrote:

            > I can understand that there ARE diferences? I do not understand
            > when to use which one.

            It is conjectured that btree is perhaps better for random-access
            read-write databases where Postfix maintains an update cursor for
            cleanup of stale entries. This may not be true, but it has certainly
            worked well enough in practice, and following the herd is reasonably
            sound in this case.

            > For example I have heard about the LMDB format from the OpenLDAP
            > project.? I hear that it is fast and lightweight and some persons
            > say one of the best options.

            LMDB in Postfix is new. It may be a good replacement for Berkeley
            DB, time will tell.

            > smtpd_tls_session_cache_database = lmdb:/var/lib/postfix/smtpd_scache
            > smtp_tls_session_cache_database = lmdb:/var/lib/postfix/smtp_scache
            >
            > alias_maps = lmdb:/etc/aliases

            If you're willing to be on the bleeding edge, you're free to test these.

            --
            Viktor.
          • Wietse Venema
            ... Wietse ... If you don t know what to use, use the documentation examples. The examples will do a reasonable job. If you were expecting a free lecture about
            Message 5 of 10 , Jul 12, 2014
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              Arun:
              >I can understand that there ARE diferences. I do not understand
              >when to use which one.

              Wietse
              >In that case, I suggest that you use what is shown the examples.
              >Every type (hash, btree, lmdb, and so on) presents a compromise
              >between different requirements.
              >
              > I suggest that you use what is shown the examples.

              Arun:
              >Is it wrong to ask questions? Is 'why' not allowable ? I guess it
              >is because you say so!

              If you don't know what to use, use the documentation examples.
              The examples will do a reasonable job.

              If you were expecting a free lecture about the pros and cons of
              hash versus btree versus lmdb and so on, then sorry, I consider
              that an unreasonable expectation.

              Wietse
            • lists@rhsoft.net
              ... maybe somebody else would have answered something different than use the Postfix documentation - demand from others always be nice and friendly should
              Message 6 of 10 , Jul 12, 2014
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                Am 12.07.2014 14:13, schrieb Wietse Venema:
                > Arun:
                >> Is it wrong to ask questions? Is 'why' not allowable ? I guess it
                >> is because you say so!
                >
                > If you don't know what to use, use the documentation examples.
                > The examples will do a reasonable job.
                >
                > If you were expecting a free lecture about the pros and cons of
                > hash versus btree versus lmdb and so on, then sorry, I consider
                > that an unreasonable expectation

                maybe somebody else would have answered something different
                than "use the Postfix documentation" - demand from others
                always be nice and friendly should lead in practice what
                you preach
              • Wietse Venema
                ... It s time for me to stop trying to help people, because there are too many who read hostile intent in my replies. Wietse
                Message 7 of 10 , Jul 12, 2014
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                  lists@...:
                  >
                  > Am 12.07.2014 14:13, schrieb Wietse Venema:
                  > > Arun:
                  > >> Is it wrong to ask questions? Is 'why' not allowable ? I guess it
                  > >> is because you say so!
                  > >
                  > > If you don't know what to use, use the documentation examples.
                  > > The examples will do a reasonable job.
                  > >
                  > > If you were expecting a free lecture about the pros and cons of
                  > > hash versus btree versus lmdb and so on, then sorry, I consider
                  > > that an unreasonable expectation
                  >
                  > maybe somebody else would have answered something different
                  > than "use the Postfix documentation" - demand from others
                  > always be nice and friendly should lead in practice what
                  > you preach

                  It's time for me to stop trying to help people, because
                  there are too many who read hostile intent in my replies.

                  Wietse
                • lists@rhsoft.net
                  ... no - i only tried to point out that responses sometimes appear to have unfriendly or bad intention even if they are not meant that way it s the same as you
                  Message 8 of 10 , Jul 12, 2014
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                    Am 12.07.2014 14:35, schrieb Wietse Venema:
                    > lists@...:
                    >> Am 12.07.2014 14:13, schrieb Wietse Venema:
                    >>> Arun:
                    >>>> Is it wrong to ask questions? Is 'why' not allowable ? I guess it
                    >>>> is because you say so!
                    >>>
                    >>> If you don't know what to use, use the documentation examples.
                    >>> The examples will do a reasonable job.
                    >>>
                    >>> If you were expecting a free lecture about the pros and cons of
                    >>> hash versus btree versus lmdb and so on, then sorry, I consider
                    >>> that an unreasonable expectation
                    >>
                    >> maybe somebody else would have answered something different
                    >> than "use the Postfix documentation" - demand from others
                    >> always be nice and friendly should lead in practice what
                    >> you preach
                    >
                    > It's time for me to stop trying to help people, because
                    > there are too many who read hostile intent in my replies

                    no - i only tried to point out that responses sometimes
                    appear to have unfriendly or bad intention even if they
                    are not meant that way

                    it's the same as you and Victor yesterday assumed bad
                    intention in two posts of me finally with "Stupid
                    knee-jerk reactions"

                    in doubt assume good intentions even in case of bad
                    chosen wording could prevent a lot of heat
                  • Titanus Eramius
                    I m sorry, but this thread seems to have taken a detour. Being a Dane, I run into these kinds of responses all the time, simply because I find it
                    Message 9 of 10 , Jul 12, 2014
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                      I'm sorry, but this thread seems to have taken a detour. Being a Dane,
                      I run into these kinds of responses all the time, simply because I find
                      it counter-productive to sugarcoat things when writing English.

                      On Sat, 12 Jul 2014 14:41:51 +0200
                      "lists@..." <lists@...> wrote:

                      > Am 12.07.2014 14:35, schrieb Wietse Venema:
                      > > lists@...:
                      > >> Am 12.07.2014 14:13, schrieb Wietse Venema:
                      > >>> Arun:
                      > >>>> Is it wrong to ask questions? Is 'why' not allowable ? I guess it
                      > >>>> is because you say so!

                      No, because it's already said in the docs, at Wikipedia, Google, ...
                      Why should all this be explained again, when lots and lots of pages
                      already covers it? And why is that not OK?

                      > >>> If you don't know what to use, use the documentation examples.
                      > >>> The examples will do a reasonable job.
                      > >>>
                      > >>> If you were expecting a free lecture about the pros and cons of
                      > >>> hash versus btree versus lmdb and so on, then sorry, I consider
                      > >>> that an unreasonable expectation
                      > >>
                      > >> maybe somebody else would have answered something different
                      > >> than "use the Postfix documentation" - demand from others
                      > >> always be nice and friendly should lead in practice what
                      > >> you preach
                      > >
                      > > It's time for me to stop trying to help people, because
                      > > there are too many who read hostile intent in my replies
                      >
                      > no - i only tried to point out that responses sometimes
                      > appear to have unfriendly or bad intention even if they
                      > are not meant that way
                      >
                      > it's the same as you and Victor yesterday assumed bad
                      > intention in two posts of me finally with "Stupid
                      > knee-jerk reactions"
                      >
                      > in doubt assume good intentions even in case of bad
                      > chosen wording could prevent a lot of heat

                      Yeah well, this should go both ways, but clearly does not. I would
                      always prefer a short, no bullshit / sugarcoated answer, but apparently
                      someone has concluded we can't use those, because someone gets upset.

                      How can this even be an issue here, on a technical mailing list?
                    • lists@rhsoft.net
                      ... me too, german native speaker ... Docs and Wikipedia are not the same as asking for practical expierience especially in case of new options, Wikipedia says
                      Message 10 of 10 , Jul 12, 2014
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                        Am 12.07.2014 17:34, schrieb Titanus Eramius:
                        > I'm sorry, but this thread seems to have taken a detour. Being a Dane,
                        > I run into these kinds of responses all the time, simply because I find
                        > it counter-productive to sugarcoat things when writing English.

                        me too, german native speaker

                        >>>>>> Is it wrong to ask questions? Is 'why' not allowable ? I guess it
                        >>>>>> is because you say so!
                        >
                        > No, because it's already said in the docs, at Wikipedia, Google, ...
                        > Why should all this be explained again, when lots and lots of pages
                        > already covers it? And why is that not OK?

                        Docs and Wikipedia are not the same as asking for practical
                        expierience especially in case of new options, Wikipedia says
                        how things are in theory but not that often explains pitfalls

                        docs are mostly fine for expierienced people understanding a
                        lot of things because of their context but as starting point
                        difficult

                        > Yeah well, this should go both ways, but clearly does not. I would
                        > always prefer a short, no bullshit / sugarcoated answer, but apparently
                        > someone has concluded we can't use those, because someone gets upset

                        well, that's the same on any english mailing-list
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