<p>This site was first published in the early 2000s. At the inception, it didn't contain a blog. It was just a bunch of pages thrown together with PHP - that's how it was usually done those days. Then I started blogging but initially it was on Blogger. Over time, the site was powered by various other blogging software, including MovableType, GreyMatter, and WordPress (hangs head in shame)</p><p>The most recent version of the site was a custom-built CMS using Django and stored on Google Cloud DataStore. However, the author found the technology to be difficult and unenjoyable to work with, leading to a lack of updates on the site for several years.</p><p>Recently, I decided to revamp the site using Next.js and merge the blog and non-blog content together. Since the export tools for App Engine and DataStore weren't all that great, I used wget and cheerio to scrape my own site instead of using those tools.</p>

Reborn as  a Next.js website

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            <p>Right-O Jeeves, I downloaded the Northwind backup for sql server, but how do I restore it with sqlcmd? The butler answered:</p>

            <p><code>RESTORE DATABASE Northwind FROM DISK='/tmp/Northwind.bak'</code></p>

            <p>But that produced</p>

            <pre>Msg 3201, Level 16, State 2, Server 61ea3d23c7fb, Line 1
Cannot open backup device '/tmp/Northwind.bak'. Operating system error 2(The system cannot find the file specified.).
Msg 3013, Level 16, State 1, Server 61ea3d23c7fb, Line 1
RESTORE DATABASE is terminating abnormally.
</pre>

            <p>Jeeves isn't in top form these days. Either that or he is still smarting over that incident of the purple socks. He left me scratching around and I figured out for myself that you need to move the file to the location where sql server's data is peristed. In my case, I started the docker container as :</p>

            <pre>docker run -d -e 'ACCEPT_EULA=Y' -e 'SA_PASSWORD=*****'   -p 1433:1433 -v /var/opt/mssql:/var/opt/mssql -d microsoft/mssql-server-linux</pre>

            <p>This means that the Northwind.bak file has to be copied to '/var/opt/mssql', and then</p>

            <pre>Directory lookup for the file "D:\MSSQLDataFiles\UNTC\DB_All\DB\NORTHWND.MDF" failed with the operating system error 2(The system cannot find the file specified.).
Msg 3156, Level 16, State 3, Server 61ea3d23c7fb, Line 1
File 'Northwind' cannot be restored to 'D:\MSSQLDataFiles\UNTC\DB_All\DB\NORTHWND.MDF'. Use WITH MOVE to identify a valid location for the file.
Msg 5133, Level 16, State 1, Server 61ea3d23c7fb, Line 1
Directory lookup for the file "D:\MSSQLDataFiles\UNTC\DB_All\DB\NORTHWND_log.ldf" failed with the operating system error 2(The system cannot find the file specified.).
Msg 3156, Level 16, State 3, Server 61ea3d23c7fb, Line 1
File 'Northwind_log' cannot be restored to 'D:\MSSQLDataFiles\UNTC\DB_All\DB\NORTHWND_log.ldf'. Use WITH MOVE to identify a valid location for the file.
Msg 3119, Level 16, State 1, Server 61ea3d23c7fb, Line 1
Problems were identified while planning for the RESTORE statement. Previous messages provide details.
Msg 3013, Level 16, State 1, Server 61ea3d23c7fb, Line 1
RESTORE DATABASE is terminating abnormally.
</pre>

            <p>This is paydirt! According to <a href="https://msdn.microsoft.com/en-us/library/mt710790.aspx">MSDN</a>, you need to make a close note of these paths, and change your restore command in sqlcmd appropriatelty. Something like:</p>

            <p><code>RESTORE DATABASE Northwind FROM DISK='/var/opt/mssql/Northwind.bak' WITH MOVE 'Northwind' TO 'D:\MSSQLDataFiles\UNTC\DB_All\DB\NORTHWND.MDF', MOVE 'Northwind_log' TO 'D:\MSSQLDataFiles\UNTC\DB_All\DB\NORTHWND.LDF'</code></p>

            <p>What, still the same error!! Then I found a stackoverflow answer that lead me down the right track. You have to use the actual file system paths on linux rather than the virtual paths that are shown in the error.</p>

            <p><code>RESTORE DATABASE Northwind FROM DISK='/var/opt/mssql/Northwind.bak' WITH MOVE 'Northwind' TO '/var/opt/mssql/data/NORTHWND.MDF', MOVE 'Northwind_log' TO '/var/opt/mssql/data/NORTHWND_log.ldf' Go </code></p>

            <p>What-ho! What-ho! What-ho!</p>


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Restoring a database on ms sql server for linux (docker)

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            <h3>Ancient history.</h3>

            <p>These bundles are known by many different names like XAMPP, WAMPP, LAMPP etc. They all have a few things in common, such as&nbsp;&nbsp;PHP, MySql and Apache being bundle installer togther with a bunch of other stuff like Wordpress, Joomla and phpmyadmin. Sometimes Apache makes way for nginx. These bundles&nbsp;were very popular a decade ago and sadly even today they are used far more often than they should be. These were and still are primarily used by developers on their desktops. The reason for their popularity was the fact that one does not need to seperately install any of the servers but instead they are all installed with reasonable defaults.</p>

            <p>All these bundles are obsolete now rather they became obsolete as far back&nbsp;march 2012.</p>

            <h3>PHP Development server.</h3>

            <p>When php 5.4 was released in 2012, it completely eleminated the need to setup apache for development enviorenments. This is thanks to the inclusion of a PHP built in webserver. Since then all that was needed to test your scripts locally was to enter the terminal, move into the folder with the scripts and just type</p>

            <p><code>php -S localhost:8000</code></p>

            <p>And the built in webserver would immidiately start to deliver your files. You can view them in the browser just as you would with apache.</p>

            <h3>What about mysql?</h3>

            <p>Exactly! What about mysql? First of all do you really need mysql? Don't be put off by the lite in sqlite. It's a fantastic database and it's perfectly capable of powering almost all the websites out there. Let's admit it almost all the websites out there including this one get's very little traffic. A vast majority of the page views on almost any website doesn't result in a database write operation. Sqlite may suck at write operations but it handles read operations really&nbsp;well. So whenever possible switch to sqlite and do away with all that hassle.</p>

            <p>On the other hand if you really do need to use mysql, it's fairly straightforward to install the server from the downloads available for your operating system on the mysql website. Alternatively you could install mariadb or percona server.</p>

            <p>Using this approach helps to avoid having too many black boxes in your system. Often while working with mentees i've had to ask where are your errors logs? Where is the php.ini file why are you not using a debugger and an IDE and often they didn't have an answer due to the fact they had used a bundle. And these bundles make it very hard to customize each installation to meet your requirements + updating individual paakges are a nightmare.</p>


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Why you shouldn't use PHP + MySql + Apache bundles

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            <p>Having decided to <a href="sql-server-on-linux">establish friendly relations with microsoft SQL server</a> after an estrangement of nearly 15 years,&nbsp;I am playing around with SQL server on linux installed via docker.&nbsp; Here are some more of the interesting issues that I encountered.</p>

            <h3>Table Variables.</h3>

            <p>Why on earth does SQL server define something called a table variable.&nbsp;</p>

            <p><code>DECLARE @HelloWorld TABLE (<br>
                    &nbsp; &nbsp; ID INT IDENTITY,<br>
                    &nbsp; &nbsp; Description VARCHAR(1000)<br>
                    )</code></p>

            <p>Why not use the more common temporary table? well mssql has them too, been having them for a longer time. One SO Q&amp;A has a lengthy discussion on this and one thing that jumped out is:</p>

            <p><span style="color: rgb(36, 39, 41); font-family: Arial, &quot;Helvetica Neue&quot;, Helvetica, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);">Temporary Tables are real tables so you can do things like CREATE INDEXes, etc. If you have large amounts of data for which accessing by index will be faster then temporary tables are a good option</span></p>

            <p>When I first started on mysql ever so long ago, I always used temporary tables, those days mysql didn't have subqueries and all these years later, mysql subqueries are appallingly slow. On postgresql i've never ever created a temporary table just checked the syntax and<a href="https://www.postgresql.org/docs/9.1/static/sql-createtable.html"> it says</a></p>

            <p><span style="font-family: verdana, sans-serif; font-size: 12.16px; background-color: rgb(255, 255, 255);">Although the syntax of&nbsp;</span><tt class="LITERAL" style="font-size: 1.3em; background-color: rgb(255, 255, 255);">CREATE TEMPORARY TABLE</tt><span style="font-family: verdana, sans-serif; font-size: 12.16px; background-color: rgb(255, 255, 255);">&nbsp;resembles that of the SQL standard, the effect is not the same. In the standard, temporary tables are defined just once and automatically exist (starting with empty contents) in every session that needs them.&nbsp;</span><span class="PRODUCTNAME" style="font-family: verdana, sans-serif; font-size: 12.16px; background-color: rgb(255, 255, 255);">PostgreSQL</span><span style="font-family: verdana, sans-serif; font-size: 12.16px; background-color: rgb(255, 255, 255);">&nbsp;instead requires each session to issue its own&nbsp;</span><tt class="LITERAL" style="font-size: 1.3em; background-color: rgb(255, 255, 255);">CREATE TEMPORARY TABLE</tt><span style="font-family: verdana, sans-serif; font-size: 12.16px; background-color: rgb(255, 255, 255);">&nbsp;command for each temporary table to be used. This allows different sessions to use the same temporary table name for different purposes, whereas the standard's approach constrains all instances of a given temporary table name to have the same table structure.</span></p>

            <p>Mysql also follows the ansi syntax but behaviour is the same as in postgresql. sql server also behaves the same but the syntax is different</p>

            <p><code>CREATE&nbsp;TABLE #HelloWorld (<br>
                    &nbsp; &nbsp; ID INT IDENTITY,<br>
                    &nbsp; &nbsp; Description VARCHAR(1000)<br>
                    )</code></p>

            <p>Temporary tables are identified by a # prefix to the name.</p>

            <h2>Limit and Offset</h2>

            <p>the last version of MSSQL that i worked with was SQL Server 2000. That didn't have the LIMIT clause but had something else; TOP. If you wanted to use an OFFSET you had tie yourself up in knots. While I was away they had introduced window functions, so you can now use the <code>ROW_NUMBER</code> partition function, which made things slightly easier.</p>

            <pre class="lang-sql prettyprint prettyprinted" style="margin-bottom: 1em; padding: 5px; border-width: 0px; border-style: initial; border-color: initial; width: auto; max-height: 600px; font-family: Consolas, Menlo, Monaco, &quot;Lucida Console&quot;, &quot;Liberation Mono&quot;, &quot;DejaVu Sans Mono&quot;, &quot;Bitstream Vera Sans Mono&quot;, &quot;Courier New&quot;, monospace, sans-serif; background-color: rgb(239, 240, 241); color: rgb(57, 51, 24); word-wrap: normal;"><code style="margin: 0px; border: 0px; font-size: 13px; font-family: Consolas, Menlo, Monaco, &quot;Lucida Console&quot;, &quot;Liberation Mono&quot;, &quot;DejaVu Sans Mono&quot;, &quot;Bitstream Vera Sans Mono&quot;, &quot;Courier New&quot;, monospace, sans-serif; background-color: rgb(239, 240, 241); white-space: inherit;"><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">SELECT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">  </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">*</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">
</span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">FROM</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">    </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">(</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">
        </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">SELECT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">  </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">TOP</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; color: rgb(125, 39, 39);">20</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">
                t</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">.*,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> ROW_NUMBER</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">()</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">OVER</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">(</span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">ORDER</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">BY</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> field1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">AS</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> rn
        </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">FROM</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">    table1 t
        </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">ORDER</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">BY</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">
                field1
        </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> t
</span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; color: rgb(16, 16, 148);">WHERE</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">   rn </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);">&gt;</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; color: rgb(48, 51, 54);"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; color: rgb(125, 39, 39);">10</span></code></pre>

            <p>&nbsp;</p>

            <p>In 2012, they apparently<a href="https://stackoverflow.com/a/9241984/267540" style="background-color: rgb(204, 222, 221);"> introduced OFFSET and FETCH keywords</a>&nbsp;&nbsp;which is very different to offset in say postgresql. And the FETCH keyword is an unnecessary complicated way for doing LIMIT,OFFSET, complicated but at least it works. Here is a query on Northwinds</p>

            <p><code>SELECT * FROM customers ORDER BY contactname OFFSET 0 ROWS FETCH NEXT 5 ROWS ONLY</code></p>

            <p>It must be added that LIMIT is not part of ANSI SQL but it's very common.</p>

            <p>&nbsp;</p>

            <p>&nbsp;</p>

            <p>&nbsp;</p>


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Getting back to SQL Server

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            <h3>I am feeling lucky.</h3>

            <p>In theory if you use django, changing your RDBS from say sqlite to mysql is a breeze. Simple as generating a dump of your existing data with <code>./manage.py dumpdata</code>, change database connection string in settings.py and perform&nbsp; a<code>./manage.py migrate</code> on the new backend. Now you can import the previously exported data through <code>./manage.py loaddata</code>&nbsp;. Well that's the theory but in practice there's always a glitch.</p>

            <h3>Squash Migrations</h3>

            <p>The .<code>/manage.py migrate</code> step on the new database invariably throws&nbsp;an error or two dozen. Squashing migrations often works. The idea behind squash is to take a series of create and alter statements and combine them together into one single create statement. That doesn't always work either. Then the simplest fix is to delete all the migrations from each app's migrations/ folder.&nbsp; Then a fresh&nbsp;<code>./manage.py makemigrations</code> followed by ./manage.py migrate . Now even if your luck didn't hold the first time, you are still likely to end up with a newly&nbsp;created database on your hot new server. You can now use the loaddata management command to put the data back in.</p>

            <p>The migration can stil fail in some edge cases. For example you may find that some of the model fields you have used such as ArrayField)are incompatible with the new RDBMS you are moving to. I leave you to solve that yourself with the reminder that ArrayField should never have been used in the first place. And the moral of the story is that you shouldn't rely too heavily on non standard vendor specific features and extensions present in your RDBMS.</p>

            <p>&nbsp;</p>

            <h3>Odo</h3>

            <p>Anyone who has ever tried to use Django's loaddata command can tell you that it will choke on the django Content Types app. Once you get past that hurdle, you will still find all sorts of errors popping up. Of course you can use MySql's <code>SELECT INTO OUTFILE</code> or Postgresql's <code>COPY</code> command to make the import export process less painfull but the only catch is if you have a large number of models, you will find yourself doing a lot of typing. Enter Odo.</p>

            <pre>import os, sys

if __name__ == '__main__': #pragma nocover
    # Setup environ
    sys.path.append(os.getcwd())

    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "myapp.settings")

    import django
    django.setup()

from odo import odo
from django.apps import apps

for m in apps.get_models():
    odo("sqlite://db.sqlite3::{0}".format(m._meta.db_table),"/tmp/{0}.csv".format(m._meta.db_table))
</pre>

            <p>The above code will export data from every single table in your database into a set of CSV files using sqlite's .output command for the export, while most home brewed exporters would save the data line by line. Right now, you can import these into another database right? What if I told you that you can actually import export without intermediate CSV dumps? yep, quite possible but your milage might vary.</p>


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Changing the backend db of a live django app.

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            <p><strong>TLDR;</strong> Need to connect to microsoft sql server from your linux desktop? DBeaver maybe your best bet.</p>

            <h3>sqlcmd</h3>

            <p>My opinion of sqlcmd is that it sucks like most everything else by Microsoft.&nbsp;I am no fan of their technology&nbsp;but sometime in my line of work I do have close encounters with them. I try to avoid it as much as possible but sometimes , there's no choice. Microsoft SQL server is a product that I need to work with every once in a whie.&nbsp;&nbsp;Rather than sqlcmd, I thought to try out VS&nbsp;Code to connect to the sql server. Unfortunately I had to upgrade my Linux Mint Version due partly to inistallation conflicts that sqlcmd had with it (Mint Rosa). But what do I get when I try to run the sql-server extension on VS Code?</p>

            <pre>Failed to load sql tools service </pre>

            <h3>HeidiSQL</h3>

            <p>This is a known issue with <a href="https://github.com/Microsoft/vscode-mssql/issues/364">Mint 18.</a>&nbsp;It will probably be fixed soon but rather than waiting for it, I thought to try our HeidiSQL, which works under wine. I am perfectly happy with using psql client for postgersql and the mysql console for mysql but having a single GUI that can connect to all three does have it's advantages too. But it will apparently not work out of the box with mssql&nbsp;</p>

            <p class="text-center"><img class="thumbnail" src="https://s3.amazonaws.com/images.raditha.com/blog/images/2016/heidisql.png"></p>

            <p>Once you install native_mdac and mdac28&nbsp;you need to close and open heidisql again. Oh, one more thing, it's heidiSQL portable that worked for me rather than the standard download. The standard download complained about a missing mysql.dll but the portable version worked with both mysql and mssql but not so postgresql. Heidi would complain about a missing libpq.dll which is there in the same folder at heideisql.exe. Typing `wine heidisql.exe` from the command line reveals:</p>

            <pre>err:module:import_dll Library MSVCR120.dll (which is needed by L"C:\\heidi\\LIBEAY32.dll") not found
err:module:import_dll Library LIBEAY32.dll (which is needed by L"C:\\heidi\\SSLEAY32.dll") not found
err:module:import_dll Library MSVCR120.dll (which is needed by L"C:\\heidi\\SSLEAY32.dll") not found
err:module:import_dll Library SSLEAY32.dll (which is needed by L"C:\\heidi\\libpq.dll") not found
err:module:import_dll Library MSVCR120.dll (which is needed by L"C:\\heidi\\LIBEAY32.dll") not found
err:module:import_dll Library LIBEAY32.dll (which is needed by L"C:\\heidi\\libpq.dll") not found
err:module:import_dll Library MSVCR120.dll (which is needed by L"C:\\heidi\\libpq.dll") not found
</pre>

            <p>Apparently this can be fixed by installing vcrun13 in winetricks, but winetricks just hangs on it without producing any output.</p>

            <h3>DBeaver</h3>

            <p>So I decided to ditch all these and switch to DBeaver. <a href="http://dbeaver.jkiss.org/">DBeaver</a> is JDBC and automatically downloads the driver. So it works with practically any RDBMS and CSV files too! DBeaver also has the advantage being compatible with almost any SQL or noSQL database.&nbsp;</p>


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Database clients for Microsft SQL server on linux.

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            <p>I hate updating my OS.&nbsp;I only do so when I am left with no choice, like when so many packages conflicts appear as they are doing now. This time around the conflicts are&nbsp;related Oracle and SQL Server clients on Mint 17.3 (Ubuntu 14.04). In the old days upgrading mint was particularly diffcult because it doesn't have the 'dist upgrade' option found in other ubuntu deravatives. But luckily mintupgrade has appeared on the scene in recent times. It's rather slow but at least the computer is usable while the upgrade process is running. Whatever method&nbsp;you use for the upgrade, there are always one or two post upgrade issues. This is what Mint Sara (18) (Ubuntu 16.04)) came up with.</p>

            <h3>missing datetime in python.</h3>

            <p>Trying to start the django dev server with ./manage.py shell and this is the result:</p>

            <pre>Traceback (most recent call last):
&nbsp; File "./manage.py", line 8, in &lt;module&gt;
&nbsp; &nbsp; from django.core.management import execute_from_command_line
&nbsp; File "/usr/local/virtual-django9/local/lib/python2.7/site-packages/django/__init__.py", line 1, in &lt;module&gt;
&nbsp; &nbsp; from django.utils.version import get_version
&nbsp; File "/usr/local/virtual-django9/local/lib/python2.7/site-packages/django/utils/version.py", line 3, in &lt;module&gt;

&nbsp; &nbsp; import datetime
ImportError: No module named datetime</pre>

            <p>The <a href="https://askubuntu.com/a/542673/453812">solution</a> apparently is to replace the python binary in the virtualenv. I still haven't figured out why exactly that is so, but it certainly worked.</p>

            <h3>gvim and python</h3>

            <pre>Error detected while processing /home/raditha/.vimrc: 
line &nbsp; &nbsp;3: 
E319: Sorry, the command is not available in this version: py &lt;&lt; EOF</pre>

            <p>What solved it was a comment on an <a href="https://askubuntu.com/a/750768/453812">askubuntu answer</a></p>

            <p><span style="color: rgb(17, 17, 17); font-family: Ubuntu, Arial, &quot;libra sans&quot;, sans-serif; font-size: 13px; background-color: rgb(255, 255, 255);">Python3 is default interpreter for Ubuntu 16.04. If this message appears as a result of using&nbsp;</span><code style="margin: 0px; padding: 1px 5px; border: 0px; font-size: 13px; font-family: Consolas, Menlo, Monaco, &quot;Lucida Console&quot;, &quot;Liberation Mono&quot;, &quot;DejaVu Sans Mono&quot;, &quot;Bitstream Vera Sans Mono&quot;, &quot;Courier New&quot;, monospace, sans-serif; background-color: rgb(239, 240, 241); white-space: normal; color: rgb(17, 17, 17);">py</code><span style="color: rgb(17, 17, 17); font-family: Ubuntu, Arial, &quot;libra sans&quot;, sans-serif; font-size: 13px; background-color: rgb(255, 255, 255);">command, replace it by Python 3 equivalent&nbsp;</span></p>

            <h3>gvim, python and execfile</h3>

            <p>That still leaves me with the following problem:</p>

            <pre>line &nbsp; 12:
Traceback (most recent call last):
&nbsp; File "&lt;string&gt;", line 8, in &lt;module&gt;
NameError: name 'execfile' is not defined</pre>

            <p>The fix&nbsp;is described here: <a href="https://stackoverflow.com/a/6357418/267540">http://stackoverflow.com/a/6357418/267540</a></p>

            <p>After both these changes, the first part of my .vimrc looks like this</p>

            <pre>py3 &lt;&lt; EOF
import os.path
import sys
import vim
if 'VIRTUAL_ENV' in os.environ:
&nbsp; &nbsp; project_base_dir = os.environ['VIRTUAL_ENV']
&nbsp; &nbsp; sys.path.insert(0, project_base_dir)
&nbsp; &nbsp; activate_this = os.path.join(project_base_dir, 'bin/activate_this.py')
&nbsp; &nbsp; exec(compile(open(activate_this,"rb").read(), activate_this, 'exec'), dict(__file__=activate_this))
EOF</pre>

            <p>Interestingly both the above vim/gvim related errors appear only when gvim is started after the virtualenv has been activated.&nbsp;</p>


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            <p>It's been more than 15 years since I last opened a connection to a microsoft&nbsp;SQL Server. Since Mircrosoft has embracced open source in general and linux in particular it seems like a good time to try it once again. Particularly since you can now run SQL server on linux thanks to docker.</p>

            <p>I setup sql server on my linux machine using the<a href="https://hub.docker.com/r/microsoft/mssql-server-linux/"> official docker image</a> provided by microsoft. However when ever the server was started according to the instructions the container would run for a few seconds and then shut down. If you try to connect to it during the brief period when it's alive, you get an error like this from sqlcmd:</p>

            <pre>Sqlcmd: Error: Microsoft ODBC Driver3 for SQL Server : Client unable to establish connection because an error was encountered during handshakes before login. Common causes include client attempting to connect to an unsupported version of SQL Server, server too busy to accept new connections or a resource limitation (memory or maximum allowed connections) on the server..
Sqlcmd: Error: Microsoft ODBC Driver3 for SQL Server : TCP Provider: Error code 0x68.
Sqlcmd: Error: Microsoft ODBC Driver3 for SQL Server : Client unable to establish connection.
Sqlcmd: Error: Microsoft ODBC Driver3 for SQL Server : Client unable to establish connection due to prelogin failure.</pre>

            <p>Searched around for quite a bit but no solid answer was found. Then I re read the instructions again. Apparently this innocuous looking bit is rather important:</p>

            <ul style="box-sizing: inherit; list-style-position: outside; font-family: &quot;Helvetica Neue&quot;, Helvetica, Roboto, Arial, sans-serif; margin-right: 0px; margin-bottom: 1.25rem; margin-left: 1.1rem; padding: 0px; font-size: 16px; line-height: 1.6; color: rgb(85, 85, 85); background-color: rgb(255, 255, 255);">
                <li style="box-sizing: inherit; margin: 0px; padding: 0px;">A strong system administrator (SA) password: At least 8 characters including uppercase, lowercase letters, base-10 digits and/or non-alphanumeric symbols.</li>
            </ul>

            <p>If you specify too short a password the server apparently doesn't start or dies off immediately. When you run a docker image as a daemon, the container also shuts down if there are no processes running inside it. Rather lame but there are you.</p>

            <p>Update:</p>

            <p>To make the data persist you have to pass the container a path on the local file system for read and write. The official document says pass the parameter like what's given below, but it forgets to tell you what exactly should go into the <em>host directory</em> flag.</p>

            <pre>-v &lt;host directory&gt;:/var/opt/mssql
</pre>

            <p>Almost anything will do. I used <code>-v /var/opt/mssql:/var/opt/mssql</code></p>


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SQL Server on Linux

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            <p>Now it's time for the die hard Django fan to learn ASP.Net. Once upon a long ago, around the time that Asp.Net was born I worked with a guy who had practially every single Microsoft&nbsp;certificate they had on offer. We were constantly arguing about which is better PHP or ASP. Those days PHP was crap (and now it's worse) but it was still&nbsp;a whole lot&nbsp;better than ASP. So much so that when my friend started out on his own, his shop only dealt with PHP and refused to touch&nbsp;Asp or ASP.Net. Now things have come a full circle.&nbsp;</p>

            <p>Yesterday, I made an attempt to learn C# in 24 hours. Heck it didn't take 24 hours, mostly because the language is a lot like Java and the parts that are not like java seems like C++ or python. As <a href="http://thameera.sexy/">Thameera</a> pointed out in a comment yesterday, it's been having Lambda's for years.</p>

            <p>Having learnt the basic stuff, I even wrote a bit of code. It was&nbsp;to parse a CSV, transform it and load it into an SQLite database. Of course I know how to load a CSV directly into SQLite (I generally prefer sqlitemon for this rather than the command line interface). But this data set needed some transformations, beside the whole point is to write some code!</p>

            <p>Apparently System.Data.Sqlite isn't available for Dot Net Core, you need to use Microsoft.Data.Sqlite and the latter is sparesly documented, but no fear, it seems to be compatible with the former.</p>

            <p>So on to Asp.Net , let's hope to finish it by this time tommorrow&nbsp;</p>


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Asp.Net in 24 hours.

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            <p>What the hell am I, an avowed microsoft hater doing with c#? <a href="http://www.networkworld.com/article/3120774/open-source-tools/microsoft-s-the-top-open-source-contributor-on-github.html">What the hell is microsoft doing on github</a>? When Visual Studio Code was announced for linux, I was more than sceptical. I scoffed at folks who tried it out. But now here I am having a crack at it myself. Right now I am on holiday at my sister's place in the hills. This is where <a href="python-in-48-hours.html">I learned python</a> a few years back. Maybe it's time to investigate&nbsp;C# . Let's see if it can be learnt in 24 hours. I will probably make a fool of myself with the comments I am making on this blog post and maybe even the next few posts as well. But never mind. The time now BTW, is 6:41 is in the morning. It's cold but very bright and sunny.</p>

            <h2>Program stucture.</h2>

            <p>The first thing that csharp hits you in the face with is <code>Namespace</code>. I rekon this is more like java packages than C++ namespaces. Inside a name space you can have classes and interfaces and we all know what they are. Less obvious was <code>Using</code>, this sounds a bit like <code>import package.*</code> in java. Shudder. But perhaps it's more like the same keyword in C++. The program entry point is <code>public static void Main(string[] args)</code> now where have I seen that before?</p>

            <h2>Types</h2>

            <p>Why does csharp have so many different types? Who in his right mind will bother with&nbsp;<code>ubyte</code>, <code>ushort</code> or <code>byte</code> instead of using plain old int? What's the good of toasting a few brain cells to save a byte of storage? And here we have the&nbsp;<code>enum</code>&nbsp; One of my pet hates. That hatred comes from the enum in SQL, but as a result I am generally averse to it's use in other languages too. Not many people use it in python but lots of java folks do.&nbsp;Ccsharp's version seems to be something&nbsp;along the same lines. The <code>struct</code> keyword is straight out of C, so why is it needed in an object oriented language?</p>

            <p>Delegates are a bit tricky, it seems to be like a pointer to a function in C which again raises the question of why it's needed, perhaps a better way to think of it would be to compare it to python function which are objects and can be passed around as parameters to other functions or perhaps Java predicates.</p>

            <p>While still on the subject of types, you can always trust microsoft to make things as complicated as possible. Proof:</p>

            <blockquote>Nullable value types also do not have to be declared before they can be used. For each non-nullable value type T there is a corresponding nullable value type T?, which can hold an additional value, null. For instance, int? is a type that can hold any 32-bit integer or the value null.</blockquote>

            <h2>Expressions</h2>

            <p>Nothing much to write home about here. Pretty much the same as almost any other language. Except for maybe <code>checked</code> and <code>unchecked</code>. If the expression is wrapped in checked it will not raise an exception if there is an arithmatic overflow.</p>

            <h2>Classes and objects</h2>

            <p>Again a well traveled path but the <code>internal</code> access modifier was something that I didn't quite get the hang of and I had to brush up on <code>virtual</code> methods to get it through to my head. After so much of Java and Python almost didn't recognize the '<code>:</code>' notation to extend a class as coming from C++. properties smell&nbsp;like @properties in python. Events and event handlers are going to take a bit of getting used to, specially because they are tied to delegates (which I am not 100%) with yet and also because event handlers are added with += and removed with -= . I suppose it does make some sense when you think about it.</p>

            <p>This is beginning to look easy. Should have tried this out long before this.</p>


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