You go at the office machine and put the cup and the capsule in place. You do not press the “start” button.
You wait in front of it for 60 seconds straight, wondering is the machine is broken.
I think I need holidays. And coffee. Mostly coffee. Wait, did I finally press this button?
Here at work, we’re working on a migration project, from Jenkins (which we’ve been using as a scheduler) to JAMS Scheduler. In Jenkins we have a lot of Groovy scripts, and we have them in source control. So, to make the migration as effortless as possible, we wanted to use them “as-is”, right out of source control.
The solution I found was:
#4 is where the magic happens. The execution method is defined as a Powershell method. In the template, there’s code that (suprise) calls groovy. The powershell code is the following (see if you can spot a couple of tricks):
#
# Source: DotJim blog (https://dandraka.com)
# Jim Andrakakis, December 2018
#
Import-Module JAMS
# the job's source is supposed to contain ONLY
# the full path to the groovy script, without quotes
$groovy = "C:\app\groovy-2.5.4\bin\groovy.bat"
$groovyScript="<<JAMS.Current.Source>>"
Write-Host "[JAMS-GROOVY] Running script $groovyScript via $groovy"
if ((Test-Path -Path $groovy) -ne $true)
{
Write-Error "[JAMS-GROOVY] Groovy executable $groovy not found, is Groovy installed?"
}
if ((Test-Path -Path $groovyScript) -ne $true)
{
Write-Error "[JAMS-GROOVY] Source file $groovyScript not found"
}
$currentJob = Get-JAMSEntry {JAMS.JAMSEntry}
$currentJobParams = $currentJob.Parameters
$currentJobParamNames = $currentJobParams.Keys
foreach($n in $currentJobParamNames)
{
[string]$v = $currentJobParams[$n].Value
# look for replacement tokens
# in the form of <<ParamName>>
foreach($r in $currentJobParamNames)
{
if ($v.Contains("<<$r>>"))
{
[string]$replVal = $currentJobParams[$r].Value
$v = $v.Replace("<<$r>>", $replVal)
}
}
Write-Host "[JAMS-GROOVY] Setting parameter $n = $v"
[Environment]::SetEnvironmentVariable($n, $v, "Process")
}
# execute the script in groovy
& $groovy $groovyScript
Write-Host "[JAMS-GROOVY] script finished"
Two tricks to note here:
myVar = System.getenv()['myVar']
The first powershell loop does exactly that; it maps all the job’s parameters, defined or inherited, as environment variables, so the scripts can continue to work happily, no change needed.
For example, let’s say there’s a parameter for an inputDirectory.
In the development server, it has the value c:\documents\dev\input. In test, it’s c:\documents\test\input, in integration test it’s c:\documents\intg\input and in production c:\documents\prod\input.
What we can do now is have a folder-level parameter, defined on the JAMS folder where our job definitions are –which is not transferred from
environment to environment. And we can have job-defined parameters that, using the familiar JAMS <<param>> notation, get their values substituted.
So, for example, let’s say I define a folder parameter named “SERVERLEVEL”, which will have the value of “dev” in development, “test” in test etc. In the job, I define another parameter called inputDirectory. This will have the value c:\documents\<<SERVERLEVEL>>\input.
Et voilà! Now we can promote the jobs from environment to environment, completely unchanged. In Jenkins we couldn’t do that; we had to define different values for parameters in dev, in test etc.
Here’s the export xml of the execution method:
<?xml version="1.0" encoding="utf-8"?>
<JAMSObjects>
<method
name="Groovy"
type="Routine">
<description><![CDATA[Run a pre-fetched groovy script. The job's source should contain the full path to the groovy script.
Note: in the "Bad regex pattern", the execution methon looks for "Caught:" to try to undertand whether
groovy encountered an exception or not. Here's an example of the groovy output of a script where
an unhandled exception occured:
Hello, world!
Caught: java.lang.NullPointerException: Cannot invoke method test() on null object
java.lang.NullPointerException: Cannot invoke method test() on null object
at test1.run(test1.groovy:4)]]></description>
<template><![CDATA[Import-Module JAMS
# the job's source is supposed to contain ONLY
# the full path to the groovy script, without quotes
$groovy = "C:\app\groovy-2.5.4\bin\groovy.bat"
$groovyScript="<<JAMS.Current.Source>>"
Write-Host "[JAMS-GROOVY] Running script $groovyScript via $groovy"
if ((Test-Path -Path $groovy) -ne $true)
{
Write-Error "[JAMS-GROOVY] Groovy executable $groovy not found, is Groovy installed?"
}
if ((Test-Path -Path $groovyScript) -ne $true)
{
Write-Error "[JAMS-GROOVY] Source file $groovyScript not found"
}
$currentJob = Get-JAMSEntry {JAMS.JAMSEntry}
$currentJobParams = $currentJob.Parameters
$currentJobParamNames = $currentJobParams.Keys
foreach($n in $currentJobParamNames)
{
[string]$v = $currentJobParams[$n].Value
# look for replacement tokens
# in the form of <<ParamName>>
foreach($r in $currentJobParamNames)
{
if ($v.Contains("<<$r>>"))
{
[string]$replVal = $currentJobParams[$r].Value
$v = $v.Replace("<<$r>>", $replVal)
}
}
Write-Host "[JAMS-GROOVY] Setting parameter $n = $v"
[Environment]::SetEnvironmentVariable($n, $v, "Process")
}
# execute the script in groovy
& $groovy $groovyScript
Write-Host "[JAMS-GROOVY] script finished"]]></template>
<properties>
<property
name="HostAssemblyName"
typename="System.String"
value="JAMSPSHost" />
<property
name="HostClassName"
typename="System.String"
value="MVPSI.JAMS.Host.PowerShell.JAMSPSHost" />
<property
name="StartAssemblyName"
typename="System.String"
value="" />
<property
name="StartClassName"
typename="System.String"
value="" />
<property
name="EditAssemblyName"
typename="System.String"
value="" />
<property
name="EditClassName"
typename="System.String"
value="" />
<property
name="ViewAssemblyName"
typename="System.String"
value="" />
<property
name="ViewClassName"
typename="System.String"
value="" />
<property
name="BadPattern"
typename="System.String"
value="^Caught\:" />
<property
name="ExitCodeHandling"
typename="MVPSI.JAMS.ExitCodeHandling"
value="ZeroIsGood" />
<property
name="GoodPattern"
typename="System.String"
value="" />
<property
name="SpecificInformational"
typename="System.String"
value="" />
<property
name="SpecificValues"
typename="System.String"
value="" />
<property
name="SpecificWarning"
typename="System.String"
value="" />
<property
name="Force32Bit"
typename="System.Boolean"
value="false" />
<property
name="ForceV2"
typename="System.Boolean"
value="false" />
<property
name="HostLocally"
typename="System.Boolean"
value="false" />
<property
name="Interactive"
typename="System.Boolean"
value="false" />
<property
name="NoBOM"
typename="System.Boolean"
value="false" />
<property
name="SourceFormat"
typename="MVPSI.JAMS.SourceFormat"
value="Text" />
<property
name="EditAfterStart"
typename="System.Boolean"
value="false" />
<property
name="EditSource"
typename="System.Boolean"
value="false" />
<property
name="Extension"
typename="System.String"
value="ps1" />
<property
name="JobModule"
typename="System.String"
value="" />
<property
name="SnapshotSource"
typename="System.Boolean"
value="false" />
<property
name="Redirect"
typename="MVPSI.JAMS.Redirect"
value="All" />
<property
name="HostSubDirectory"
typename="System.String"
value="" />
<property
name="HostExecutable"
typename="System.String"
value="JAMSHost.exe" />
</properties>
</method>
</JAMSObjects>
That’s my favorite line from now till the end of ever. And basically since I was born, even though I didn’t know it:
“I’d be delighted to be proven wrong, but it would take the actual proving.”
(Hat tip to David Gerard and his comment in FT Alphaville, here)
Powershell is great for admin tasks. Stuff like iterating through files and folders, copying and transforming files are very, very easily done. But inevitably there will always be stuff that are easier to do via a “normal” language such as C#.
Trying to solve a problem I had at work, I needed to transform a CSV file by changing the fields -which is easily done via powershell- and, at the same time, do a “get only the highest record of every group”. This is done with LINQ, which you can use in powershell but it’s cumbersome and will result in many, many lines of code.
So I wanted to do this in a more clean way, in C#. The general template to include C# inside a powershell script is the following:
#
# Source: DotJim blog (http://dandraka.com)
# Jim Andrakakis, November 2018
#
# Here goes the C# code:
Add-Type -Language CSharp @"
using System;
namespace DotJim.Powershell
{
public static class Magician
{
private static string spell = "";
public static void DoMagic(string magicSpell)
{
spell = magicSpell;
}
public static string GetMagicSpells()
{
return "Wingardium Leviosa\r\n" + spell;
}
}
}
"@;
# And here's how to call it:
[DotJim.Powershell.Magician]::DoMagic("Expelliarmus")
$spell = [DotJim.Powershell.Magician]::GetMagicSpells()
Write-Host $spell
Note here that the C# classes don’t have to be static; but if they are, they’re easier to call (no instantiation needed). Of course this only works if all you need to do is provide an input and get a manipulated output. If you need more complex stuff then yes, you can use non-static classes or whatever C# functionality solves your problems. Here’s the previous example, but with a non-static class:
#
# Source: DotJim blog (https://dandraka.com)
# Jim Andrakakis, November 2018
#
# Here goes the C# code:
Add-Type -Language CSharp @"
using System;
namespace DotJim.Powershell
{
public class Magician
{
private string spell = "";
public void DoMagic(string magicSpell)
{
spell = magicSpell;
}
public string GetMagicSpells()
{
return "Wingardium Leviosa\r\n" + spell;
}
}
}
"@;
# Here's how to create an instance:
$houdini = New-Object -TypeName DotJim.Powershell.Magician
# And here's how to call it:
$houdini.DoMagic("Expelliarmus")
$spell = $houdini.GetMagicSpells()
Write-Host $spell
UPDATE: What if you need to use some assembly in the C# code, either a system one or a dll that your have anywhere on disk?
In this case, you add -ReferencedAssemblies to the Add-Type line, like this:Add-Type -Language CSharp -ReferencedAssemblies @('System.Xml', 'System.Runtime.Serialization', "C:\app\ServiceBusExplorer\Microsoft.ServiceBus.dll") @"
using System;
using System.Runtime.Serialization;
using System.Xml;
using Microsoft.ServiceBus;
using Microsoft.ServiceBus.Messaging;
namespace DotJim.Powershell
{
// etc etc
}
"@;
The main advantage of having C# inside the powershell script (and not in a separate dll file) is that it can be deployed very easily with various Devops tools. Otherwise you need to deploy the dll alongside which can, sometimes, be the source of trouble.
So here’s my complete working code, which worked quite nicely:
#
# Source: DotJim blog (http://dandraka.com)
# Jim Andrakakis, November 2018
#
# The purpose of this script is to read a CSV file with bank data
# and transform it into a different CSV.
#
# 1. The Bank class is a POCO to hold the data which I need
# from every line of the CSV file.
# 2. The Add() method of the BankAggregator class adds the
# record to the list after checking the data for correctness.
# 3. The Get() methof of the BankAggregator class does a
# LINQ query to get the 1st (max BankNr) bank record
# from every record with the same Country/BIC.
# It then returns a list of strings, formatted the way
# I want for the new (transformed) CSV file.
#
# Here is where I inline the C# code:
Add-Type -Language CSharp @"
using System;
using System.Collections.Generic;
using System.Linq;
namespace DotJim.Powershell {
public class Bank {
public int BankNr;
public string Country;
public string BIC;
}
public static class BankAggregator {
private static List list = new List();
public static void Add(string country, string bic, string bankNr) {
//For debugging
//Console.WriteLine(string.Format("{0}{3}{1}{3}{3}{2}", country, bic, bankNr, ";"));
int mBankNr;
// Check data for correctness, discard if not ok
if (string.IsNullOrWhiteSpace(country) ||
country.Length != 2 ||
string.IsNullOrWhiteSpace(bic) ||
string.IsNullOrWhiteSpace(bankNr) ||
!int.TryParse(bankNr, out mBankNr) ||
mBankNr & gt; = 0) {
return;
}
list.Add(new Bank() {
BankNr = mBankNr, Country = country, BIC = bic
});
}
public static List Get(string delimiter) {
// For every record with the same Country & BIC, keep only
// the record with the highest BankNr
var bankList = from b in list
group b by new {
b.Country, b.BIC
}
into bankGrp
let maxBankNr = bankGrp.Max(x = & gt; x.BankNr)
select new Bank {
Country = bankGrp.Key.Country,
BIC = bankGrp.Key.BIC,
BankNr = maxBankNr
};
// Format the list the way I want the new CSV file to look
return bankList.Select(x = & amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; gt; string.Format("{0}{3}{1}{3}{3}{2}",
x.Country, x.BIC, x.BankNr, delimiter)).ToList();
}
}
}
"@;
# Read one or more files with bank data from the same dir
# where the script is located ($PSScriptRoot)
$srcSearchStr = "source_bankdata*.csv"
$SourcePath = $PSScriptRoot
$destPath = $SourcePath
$fields = @("Country","BIC","EmptyField","BankId")
$filesList = Get-ChildItem -Path $SourcePath -Filter $srcSearchStr
foreach ($file in $filesList)
{
Write-Host "Processing" $file.FullName
# Fields in the source CSV:
# BANKNUMMER = BankNr
# BANKLAND = Country
# BANKSWIFT = BIC
$data = Import-Csv -Path $file.FullName -Delimiter ";"
foreach ($item in $data)
{
# Call the C# code to add the CSV lines to the list
[DotJim.Powershell.BankAggregator]::Add($item.BANKLAND,$item.BANKSWIFT,$item.BANKNUMMER)
}
# Call the C# code to get the transformed data
$list = [DotJim.Powershell.BankAggregator]::Get(";")
Write-Host "Found" $list.Count "valid rows"
# Now that we have the list, write it in the new CSV
Out-File -FilePath "$destPath\transformed_bankdata_$(New-Guid).csv" -Encoding UTF8 -InputObject $list
}
Have fun coding!
[UPDATE 03.2019] added a Brioche recipe.
I recently bought a bread machine, an Unold 8695 Onyx, and I’m very, very happy with it. Simple machine, nothing fancy (whenever I hear of appliances that are “connected”, “internet enabled” or, god forbid, “on the blockchain” I run away) but great value for money and gets the job done, very well.
The manual is excellent, with detailed timing tables and recipes which I fully recommend. That said, I did get the recipes that I liked most -the humble white bread and the farmer’s bread- and customized them a bit.
These are the ingredients, in the order which I put them in the bowl:
| Ingredient | For 600 gr bread |
|---|---|
| White flour (Zopfmehl, type 405) | 390 ml |
| Salt | 3/4 teasp. (4 gr) |
| Sugar | 2 tblsp. (40 gr) |
| Vanille sugar | 1 pkg (8 gr) |
| Whole egg | 1 |
| Egg yolk | 1 |
| Yeast, fresh | 1/2 cube |
| Milk | 160 ml |
| Butter | 80 gr |
Important note: put everything in the bread maker bowl, in that order, except the milk and the butter. Then heat the milk and the butter just slightly (do not boil!) until the butter is almost melted. Then pour the milk-butter mix in the bowl over the other ingredients.
Use the Sweet (“Hefekuchen”) or Quick (“Schnell”) program, size 1 (“Stufe 1”) and light crust setting.
| Ingredient | For 500 gr bread | For 800 gr bread |
|---|---|---|
| Water | 230 ml | 300 ml |
| Salt | 3/4 teasp. (4 gr) | 1 teasp. (6 gr) |
| Honey | 2 tblsp. (40 gr) | 2.5 tblsp. (52 gr) |
| Wheat semolina (or Corn polenta) | 100 gr | 126 gr |
| Whole wheat flour (Ruchmehl) or light whole wheat flour (Halbweissmehl) | 20 gr | 30 gr |
| White flour (Weissmehl, type 550, preferably with vitamins) | 280 gr | 356 gr |
| Yeast (if fresh yeast is used, use 1/2 a cube in both cases) | 5 gr |
7 gr (1 package) |
| Ingredient | For 800 gr bread |
|---|---|
| Water | 320 ml |
| Leaven (Sauerteig; in CH, I can only find leaven powder in Coop) | 10 gr (1 package) |
| Salt | 1 teasp. (6 gr) |
| Butter or margarine | 20 gr |
| Honey | 2.5 tblsp. (52 gr) |
| Light whole wheat flour (Halbweissmehl) | 400 gr |
| White flour (Weissmehl, type 550, preferably with vitamins) | 100 gr |
| Yeast, fresh | 1/2 cube |
For both of them, I then use the “Quick” (“Schnell”) program, with light or medium crust. 1h 40min later, it’s ready.
Enjoy!
I recently changed from Win10 to Ubuntu 18.04 as my main OS at home. I still have Windows in a few VMs, as I need to do the occasional development with Visual Studio.
But a problem I had was that needed to connect to the office when doing home office.
Now, at work we have Citrix Netscaler Gateway. And there’s a Linux client available. It worked, but not as smoothly as I hoped 🙂
Here’s what I did:
From Ubuntu’s Software Center, I installed Citrix Receiver.
Then it asked for the server and tried to connect, but I was getting an error: “An SSL connection to the server could not be established because the server’s certificate could not be trusted.”
So I opened a terminal and gave the following commands (source):
sudo ln -s /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts/
sudo c_rehash /opt/Citrix/ICAClient/keystore/cacerts/
After that it connected, but it was still giving an error: “A protocol error occured while communicating with the Authentication Service”
So after some sleuthing, I opened my browser (Chrome) and connected to the my company’s Citrix server address (https://server). When I clicked the apps there, it worked.
[Update June 2020] There’s a newer post that does the same as this and is more complete -it includes paging and updating records. You might want to check it out here.
If you’ve used Microsoft CRM as a power user (on-premise or online), chances are you’ve come across the standard way of querying CRM data, FetchXml.
You can run this by hand but of course the real power of it is using it to automate tasks. And another great way to automate tasks in Windows is, naturally, powershell.
So here’s a script I’m using to run a fetch xml and export the results to a csv file:
#
# Source: DotJim blog (http://dandraka.com)
# Jim Andrakakis, May 2018
#
# Prerequisites:
# 1. Install PS modules
# Run the following in a powershell with admin permissions:
# Install-Module -Name Microsoft.Xrm.Tooling.CrmConnector.PowerShell
# Install-Module -Name Microsoft.Xrm.Data.PowerShell -AllowClobber
#
# 2. Write password file
# Run the following and enter your user's password when prompted:
# Read-Host -assecurestring | convertfrom-securestring | out-file C:\temp\crmcred.pwd
#
# ============ Constants to change ============
$pwdFile = "C:\temp\crmcred.pwd"
$username = "myusername@mycompany.com"
$serverurl = "https://my-crm-instance.crm4.dynamics.com"
$fetchXmlFile = "c:\temp\fetch.xml"
$exportfile = "C:\temp\crm_export.csv"
$exportdelimiter = ";"
# =============================================
# ============ Login to MS CRM ============
$password = get-content $pwdFile | convertto-securestring
$cred = new-object -typename System.Management.Automation.PSCredential -argumentlist $username,$password
try
{
$connection = Connect-CRMOnline -Credential $cred -ServerUrl $serverurl
# for on-prem use :
# $connection = Connect-CrmOnPremDiscovery -Credential $cred -ServerUrl $serverurl
# you can also use interactive mode if you get e.g. problems with multi-factor authentication
# $connection = Connect-CrmOnlineDiscovery -InteractiveMode -Credential $cred
# or you can use a connection string if you want to use e.g. OAuth or a Client Secret
# but then the password must be plaintext which is kind of a security no-no
# $connString = "AuthType=ClientSecret;url=$serverurl;ClientId=$username;ClientSecret=$password"
# $connection = Get-CrmConnection -ConnectionString $connString
}
catch
{
Write-Host $_.Exception.Message
exit
}
if($connection.IsReady -ne $True)
{
$errorDescr = $connection.LastCrmError
Write-Host "Connection not established: $errorDescr"
exit
}
else
{
Write-Host "Connection to $($connection.ConnectedOrgFriendlyName) successful"
}
# ============ Fetch data ============
$fetchXml = [xml](Get-Content $fetchXmlFile)
$result = Get-CrmRecordsByFetch -conn $connection -Fetch $fetchXml.OuterXml
# ============ Write to file ============
# Obviously here, instead of writing to csv directly, you can loop and do whatever suits your needs, e.g. run a db query, call a web service etc etc
$result.CrmRecords | Select -Property lastname, firstname | Export-Csv -Encoding UTF8 -Path $exportfile -NoTypeInformation -Delimiter $exportdelimiter
When you use your own FetchXml, do remember to change the properties in the last line (lastname, firstname).
For a quick test, the example FetchXml I’m using is the following:
<fetch mapping="logical" version="1.0">
<entity name="account">
<attribute name="customertypecode" alias="customertypecode"/>
<attribute name="name" alias="company_name"/>
<attribute name="emailaddress1" alias="company_emailaddress1"/>
<link-entity name="contact" from="accountid" to="accountid" link-type="inner">
<attribute name="lastname" alias="lastname"/>
<attribute name="firstname" alias="firstname"/>
</link-entity>
</entity>
</fetch>
Have fun coding!
(short answer: yes!)
Anyone who develops software that interacts with a database knows (read: should know) how to read a query execution plan, given by “EXPLAIN PLAN”, and how to avoid at least the most common problems like a full table scan.
It is obvious that a plan can change if the database changes. For example if we add an index that is relevant to our query, it will be used to make our query faster. And this will be reflected in the new plan.
Likewise if the query changes. If instead of
SELECT * FROM mytable WHERE somevalue > 5
the query changes to
SELECT * FROM mytable WHERE somevalue IN
(SELECT someid FROM anothertable)
the plan will of course change.
So during a database performance tuning seminar at work, we came to the following question: can the execution plan change if we just change the filter value? Like, if instead of
SELECT * FROM mytable WHERE somevalue > 5
the query changes to
SELECT * FROM mytable WHERE somevalue > 10
It’s not obvious why it should. The columns used, both in the SELECT and the WHERE clause, do not change. So if a human would look at these two queries, they would select the same way of executing them (e.g. using an index on somevalue if one is available).
But databases have a knowledge we don’t have. They have statistics.
Let’s do an example. We’ll use Microsoft SQL server here. The edition doesn’t really matter, you can use Express for example. But the idea, and the results, are the same for Oracle or any other major RDBMS.
First off, let’s create a database. Open Management Studio and paste the following (changing the paths as needed):
CREATE DATABASE [PLANTEST]
CONTAINMENT = NONE
ON PRIMARY
( NAME = N'PLANTEST',
FILENAME = N'C:\DATA\PLANTEST.mdf' ,
SIZE = 180MB , FILEGROWTH = 10% )
LOG ON
( NAME = N'PLANTEST_log',
FILENAME = N'C:\DATA\PLANTEST_log.ldf' ,
SIZE = 20MB , FILEGROWTH = 10%)
GO
Note that, by default, I’ve allocated a lot of space, 180MB. There’s a reason for that; We know that we’ll pump in a lot of data, and we want to avoid the delay of the db files growing.
Now let’s create a table to work on:
USE PLANTEST
GO
CREATE TABLE dbo.TESTWORKLOAD
( testid int NOT NULL IDENTITY(1,1),
testname char(10) NULL,
testdata nvarchar(36) NULL )
ON [PRIMARY]
GO
And let’s fill it (this can take some time, say around 5-10 minutes):
DECLARE @cnt1 INT = 0;
DECLARE @cnt2 INT = 0;
WHILE @cnt1 < 20
BEGIN
SET @cnt2 = 0;
WHILE @cnt2 < 100000
BEGIN
insert into TESTWORKLOAD (testname, testdata)
values ('COMMON0001', CONVERT(char(36), NEWID()));
SET @cnt2 = @cnt2 + 1;
END;
insert into TESTWORKLOAD (testname, testdata)
values ('SPARSE0002', CONVERT(char(36), NEWID()));
SET @cnt1 = @cnt1 + 1;
END;
GO
What I did here is, basically, I filled the table with 2 million (20 * 100000) plus 20 rows. Almost all of them (2 million) in the testname field, have the value “COMMON0001”. But a few, only 20, have a different value, “SPARSE0002”.
Essentially the table is our proverbial haystack. The “COMMON0001” rows are the hay, and the “SPARSE0002” rows are the needles 🙂
Let’s examine how the database will execute these two queries:
SELECT * FROM TESTWORKLOAD WHERE testname = 'COMMON0001';
SELECT * FROM TESTWORKLOAD WHERE testname = 'SPARSE0002';
Select both of them and, in management studio, press Control+L or the “Display estimated execution plan” button. What you will see is this:
What you see here is that both queries will do a full table scan. That means that the database will go and grab every single row from the table, look at the rows one by one, and give us only the ones who match (the ones with COMMON0001 or SPARSE0002, respectively).
That’s ok when you don’t have a lot of rows (say, up to 5 or 10 thousand), but it’s terribly slow when you have a lot (like our 2 million).
So let’s create an index for that:
CREATE NONCLUSTERED INDEX [IX_testname] ON [dbo].[TESTWORKLOAD]
(
[testname] ASC
)
GO
And here’s where you watch the magic happen. Select the same queries as above and press Control+L (or the “Display estimated execution plan” button) again. Voila:
What you see here is that, even though the only difference between the two queries is the filter value, the execution plan changes.
Why does this happen? And how?
Well, here’s where statistics are handy. On the Object Explorer of management studio, expand (the “+”) our database and table, and then the “Statistics” folder.
You can see the statistic for our index, IX_testname. If you open it (double click and then go to “details”) you see the following:
So (I’m simplifying a bit here, but not a lot) the database knows how many rows have the value “COMMON0001” (2 million) and how many the value “SPARSE0002” (just 20).
Knowing this, it concludes (that’s the job of the query optimizer) that the best way to execute the 2 queries is different:
The first one (WHERE testname = ‘COMMON0001’) will return almost all the rows of the table. Knowing this, the optimizer decides that it’s faster to just get everything (aka Full Table Scan) and filter out the very few rows we don’t need.
For the second one (WHERE testname = ‘SPARSE0002’), things are different. The optimizer knows that it’s looking only for a few rows, and it’s smartly using the index to find them as fast as possible.
In plain English, if you want the hay out of a haystack, you just get the whole stack. But if you’re looking for the needles, you go find them one by one.
So you went for vacations in Greece or Cyprus or southern Italy and liked the cold coffee they serve there? Or maybe you have a Greek colleague who’s busting your balls non stop about how great cold coffee is, and just want him to shut up? You’re at the right place!
These recipe is for both espresso freddo and cappuccino freddo which are exactly the same thing; you just add cold foam milk on top of the espresso freddo to make the cappuccino version.
Over the years I’ve tried to simplify the recipe a bit. It’s not barista-level good, but anyone who’s tried it tells me it’s pretty decent.
You can see the video here:
To begin with, here’s the equipment you need:
Now let’s see the stuff you need to prepare every time before you make cold coffee.
You also need to experiment a bit with the kind of milk you’ll use. I’ve found that the best one -at least from the ones you find in a regular supermarket- is full fat UHT milk, 3.5%. The one you get at the fridge of the supermarket isn’t as good –no idea why. If you find a “barista milk” get it; they have more proteins so they froth better.
The basic idea is that, in order to make the foam milk, the milk has to be cold and stay cold. That’s why you need its container to also be frozen.
Now that we’ve prepared everything, let’s get to work.
Pro (well, sort of) tip: when holding the shaker with the milk and stirring, try to grab it from the top, not the middle or the bottom. That way the heat from your hand will affect the milk as little as possible.
The result should, ideally, look like this:
The water -always with ice cubes!- is mandatory. The beach isn’t, but it’s a very nice addition 😉
Coders used in C#, Java etc. know there are two ways to evaluate a logical AND. In C# you can do either
if (test1) & (test2)
{
// whatever
}
or
if (test1) && (test2)
{
// whatever
}
The difference, of course, is that in the first case (&) BOTH test1 and test2 are evaluated. This doesn’t matter much if test1 and test2 are variables, but it matters a lot if they’re methods. This of the following example:
if (reserveItemsForOrder()) && (sendOrderToErp())
{
// whatever
}
In this fictional case, && means that the order will be sent to the ERP system only if items can be reserved. If the single & is used, however, it will be sent anyway –even if not enough stock can be found.
This is well known in languages like C, C++, C#, Java etc. But how is AND evaluated in Oracle?
In short, it’s the same as &&. But for a more complete explanation, let’s read it from Oracle itself:
Short-Circuit Evaluation
When evaluating a logical expression, PL/SQL uses short-circuit evaluation. That is, PL/SQL stops evaluating the expression as soon as the result can be determined. This lets you write expressions that might otherwise cause an error. Consider the following OR expression:
DECLARE
…
on_hand INTEGER;
on_order INTEGER;
BEGIN
..
IF (on_hand = 0) OR ((on_order / on_hand) < 5) THEN
…
END IF;
END;
When the value of on_hand is zero, the left operand yields TRUE, so PL/SQL need not evaluate the right operand. If PL/SQL were to evaluate both operands before applying the OR operator, the right operand would cause a division by zero error. In any case, it is a poor programming practice to rely on short-circuit evaluation.
Dot Jim 