iTunes Home Sharing doesn’t work with AppleTV when it should

For about a year, I’ve been stumped on iTunes Sharing not working on AppleTV when it worked fine between laptops. Until today, when I accidentally discovered that iTunes -> Preferences -> Sharing -> “Share Library on Network” —which
works for computers running iTunes—is not the same things as iTunes -> File -> Home Sharing, which is what AppleTV uses.

Oh well.

http://www.imore.com/itunes-9-shared-libraries-home-sharing

‘bash\r’: No such file or directory. Or, editing unix files on a Windows machine

'bash\r': No such file or directory

What does that mean, you ask yourself? It usually means you are editing *nix script files on a windows system, and then running the files on a *nix machine. For instance in docker, or a VM. Your solution is to use a text editor that allows you to save with unix line endings. `Notepad++` calls it, very reasonably, `’EOL conversion’`. Sublime text calls it `View->Line Endings`.

A further complication if you are using git is that it keeps getting reset back to windows. You could fix this with `git config core.autocrlf false` but that may have other consequences which you don’t want to bother with.

Use a public docker image in AWS ECS

Amazon Web Services carefully explain how to use a private docker image in ECS, the Amazon container service. But fails to mention what repository URL to use for a dockerhub public repository. The answer is … none at all. Just the same as the docker CLI, if you specify just namespace/imagename for a container image, ECS will pull it from dockerhub.

Postgres : Using integrated security on Windows on localhost

…is slightly less straightforward than you might hope. For MS SQL Server, integrated security implies that windows user are magically also SQL users and that no password or username is needed to login. But also, that you can no longer choose which user you login as. Postgres is more configurable and more complex. You can specify which users use SSPI and which postgres user(s) each windows user can login as. You can specify, for instance, that you are allowed to use SSPI to login as the postgres superuser.

Here is how you can login with integrated security, as the user postgres, whilst still being able to login as a different user with a password.

  1. Locate and open both your pg_hba.conf and pg_ident.conf files. I found them in C:\Program Files\PostgreSQL\data\pg96
  2. In pg_ident.conf add a line to map your windows login to the postgres user named postgres. Here’s what my line looks like:
    # MAPNAME       SYSTEM-USERNAME         PG-USERNAME
    MapForSSPI     Chris@MyMachineName    postgres

    (In normal unix style, the columns are separated by any amount of space or tab).

  3. In pg_hba.conf, add lines that allow user postgres to login with integrated security, whilst still allowing all other users to login with passwords:
    # TYPE  DATABASE        USER            CIDR-ADDRESS            METHOD
    # IPv4 local & remote connections:
    host    all             postgres        127.0.0.1/32            sspi 	map=MapForSSPI
    host    all             all             127.0.0.1/32            md5
    host    all             all             0.0.0.0/0               md5 
    # IPv6 local connections:
    host    all             postgres        ::1/128                 sspi 	map=MapForSSPI
    host    all             all             ::1/128                 md5
  4. Restart the Postgres service, for instance with a powershell command
    Restart-Service 'PostgreSQL 9.6 Server'
  5. Trying logging in as user postgres:
    • psql -h localhost -U postgres
  6. Trying logging in as some other user:
    • psql -h localhost -U someotherusercreatedwithcreaterole
      and you should be prompted for a password (unless you already mastered the pgpass.conf file)

Logging in without specifying a user name

You might expect that SSPI implies not having to specify a username. You would be wrong. Postgres still requires you specify a username when using SSPI, and, as above, allows you to choose which username.

You can however login without a username—with or without SSPI—simply by creating a postgres user (i.e., a role with LOGIN privilege) with your username. To let that user login with SSPI, you should still have a line in pg_ident.conf to map the SYSTEM-USERNAME yourname@yourmachinename to the postgres username yourname.

Integrated Security in .Net connection strings

Having done the above I can now use

"Host=localhost;Database=MyDb;Integrated Security=True;Username=postgres"

as connection string for the npgsql Ado.Net driver

Reference

https://www.postgresql.org/docs/9.4/static/auth-pg-hba-conf.html and subsequent pages on Authentication methods and the pg_ident.conf file.

Postgres quick start for MS SQL / T-SQL developers

After 17 years on T-SQL I’m at last on my first project with Postgres. Here are the first things I needed for the transition:

  • Do this first: https://wiki.postgresql.org/wiki/First_steps as it answers most of your first questions about connections, databases, using roles for logins, users and groups, and so on.
  • 'String concatenation is done with ' || 'a double pipe '.
  • No NVarchar is needed, just varchar. The default installation uses UTF-8.
  • Date & Time: use timestamp for datetime/datetime2
  • Read https://www.postgresql.org/docs/9.1/static/datatype-datetime.html for more on dates, times and intervals.
  • Use more semicolon terminators If ... Then ... ; End If ;
  • plpqsql script is separated from “pure” SQL in a way that T-SQL just doesn’t bother with. If you are writing scripts, plpqsql must either be inside a function or inside an ‘anonymous function block’, usually delimited by $$ or $somestring$; and Declare variables in one block before Begin :
    Select 'This line is plain SQL' ;
    Do $$
    Declare
      anumber integer ;
      astring varchar(100);
    Begin
    If 1=1 Then
     Raise Notice 'This block is plpgsql' ;
    End If;
    End $$ ;
    Select 'This line is SQL again' ;
    

    In fact, functions are defined in a string, and the $$…$$ delimiters is a postgres syntax for specifying a string constant without having to escape any special characters at all. They can be used anywhere in code. Functions can be defined in other languages than plpgsql. See e.g. https://pgxn.org/dist/plv8/doc/plv8.html.

  • Variables: just use a plain identifier: myvariablename with no @ symbol or other decoration. BUT as a consequnce you must avoid variable names in a query that are the same as a column name in the same query. BUT BUT in Ado.Net Commands with Parameters, still use the @parametername syntax as you would for SQL Server
  • Use Function not procedure:
    Create or Replace Function procedureName( forId int, newName varchar(20) )
    Returns int -- use returns void for no return
    As $$
    Declare 
      localvariable int;
      othervariable varchar(10);
    Begin
     Insert into mytable (id,name) values (forId, newName) On Conflict (id) Do Update Set Name=NewName ;
    End $$;
  • Ooh, did you notice how postgres has a really simple upsert syntax?
  • Postgres does function overloads, so to drop a function you must give the signature: Drop function functionname(int)
  • Whereas the T-SQLer does everything in T-SQL, other database systems use non-sql commands for common tasks. For working at a command-line, learn about psql meta-commands.. Start with \c to change database, \l to list object, and \? to list other meta commands.
  • Postgres have (I think) made more effort than MS to stay close to the SQL standards and as with T-SQL, the docs go into detail on deviations. But this means that much of your code for databases, schemas, users, tables, views, etc can be translated fairly quickly.
  • Replace Identity with Serial. For more complex options, Postgres uses SQL sequences.
  • Replace Select top 1 ... with Select ... Fetch First 1 Only.
  • role covers all of logins (Create Role ... Login) and database users (Grant Connect on Database ... TO ...) and also covers groups.
  • The Nuget package for Ado.Net, including for .Net core, is Npgsql
  • Scan these

Converting T-SQL to Postgres

Here’s my initial search/replace list for converting existing code:

Search Replace
@variableName _VariableName
NVarChar VarChar
Identity Serial
UniqueIdentifier uuid
Raise Raise Exception
Print Raise Notice
Insert Into table Select … Insert into Table (COLNAMES) Select …
If Then Begin … End Else Begin … End If Then … ; Else … ; End If ;
Create Table #Name Create Temporary Table _Name
NewId() websearch Create Extension “uuid-ossp” and then use uuid_generate_v1() or uuid_generate_v4()
Alter Function|Procedure Create or Replace Function