How can I get the BRANCH statement in the following flow service screen shot to execute the TRUE and FALSE branches?
I have the Switch set to the variable that I want: /LowerCase I set the Scope to lowercase "doug" and my MAP above the BRANCH is a LowerCase string.
For the same question, Branch can be used in two ways in the image below:
Method 1: Use branch like a switch-case statement (The first branch statement)
Method 2: Use branch like an if-else statement (The second branch statement)
Hope it helps!!
If the value of the /LowerCase field in your pipeline is "doug" then you should simply add a sub-sequence with label "doug"
Related
Does anyone have experience with removing segments from an HL7 message based on a value that exists in a field? I have seen scripts that Kill a message based on a certain value, but I would like to file the rest of the message. The language and platform being used is tcl and Cloverleaf.
I think I understand what you are after. Here's how I would remove a given OBX segment. I assume there are repeating OBX segments so this would be under an Iterate.
Add an IF statement:
If 1(0).1(0).3(%g1).OBX(0).#3(0).[1] eq =value
("value" is whatever value you are wanting this to look for.)
Then just do a pathcopy:
Source: #null
Destination: 1(0).1(0).3(%g1).OBX(0)
Of course the exact path of the OBX listed depends on the variant that you are using. But in the context of an iterate statement this should remove just the OBX with the defined value and not touch the other OBX segments.
I've searched all over the Internet and could not find a proper explanation of how backpatching works?
Can you please explain me how does backpatching works? How does it work with the markers?
I know it has 2 main types of markers:
with next-quad in it
with next-list in it
I found this code, in which they are taking an input file and creating a file with RISKI language.
In their first roll they have:
PROGRAM : N FUNCTION M MAIN_FUNCTION
and you can see that N and M are markers (they are empty rolls).
One-pass code generation has a small problem with generating code for conditionals. A typical if statement:
if CONDITION then ALTERNATIVE_1 else ALTERNATIVE_2
needs to be compiled into something like this:
compute CONDITION
JUMP_IF_TRUE label1
JUMP_IF_FALSE label2
label1:
code for ALTERNATIVE_1
JUMP label3
label2:
code for ALTERNATIVE_2
JUMP label3
label3:
next statement
But when the code for CONDITION is being generated, it is not known where label1 and label2 are, and when the code for ALTERNATIVE_1 and ALTERNATIVE_2 is being generated, it is not known where label3 is.
One way to do this is to use symbolic names for the the labels, as in the above pseudocode, and fill in the actual values when they are known. That requires storing a symbolic name in the jump statement, which complicates the datastructures (in particular, you can't just use a binary assembler code). It also requires a second pass, just to fill in jump targets.
A (possibly) simpler way is to just remember the address of the jump statements, and patch in the target address when it is known. This is known as "backpatching", because you go back and patch the generated code.
It turns out that in many cases, you end up with multiple branches to the same label. A typical case is "short-circuit" booleans like the C-family's && and || operators. For example, extending the original example:
if (CONDITION_1 and CONDITION_2) or CONDITION_3 then ALTERNATIVE_1 else ALTERNATIVE_2
compute CONDITION_1
JUMP_IF_TRUE label1
JUMP_IF_FALSE label2
label1:
compute CONDITION_2
JUMP_IF_TRUE label3
JUMP_IF_FALSE label2
label2:
compute CONDITION_3
JUMP_IF_TRUE label3
JUMP_IF_FALSE label4
label3:
code for ALTERNATIVE_1
JUMP label5
label4:
code for ALTERNATIVE_2
JUMP label5
label5:
next statement
It turns out that for simple languages, it is only necessary to remember two incomplete jump statements (often called "true" and "false"). Because there might be multiple jumps to the same target, each of these is actually a linked list of incomplete jump statements, where the target address is used to point to the next jump in the list. So the backpatching walks back through the list, patching in the correct target and using the original target to find the previous statement which needs to be patched.
What you call markers (which are an instance of what yacc/bison refers to as "Mid-Rule Productions") are not really related to backpatching. They can be used for many purposes. In one-pass code-generation, it is often necessary to perform some action in the middle of a rule, and backpatching is just one example.
For example, in the hypothetical if statement, it would be necessary to initialize the backpatch lists before the CONDITION is parsed and then backpatch at the beginning of the THEN and ELSE clauses. (Another backpatch will be triggered at the end of the parse of the entire if statement, but that one will be in the rule's finnal action.)
The easiest way to perform actions in the middle of a rule is to insert a mid-rule action, which is equivalent to inserting an empty "marker" production with an action, as in the example bison file you point to.
I have several SSIS packages that parse different files into their respective tables. Using SSIS File Watcher task, I want to create a master package that will check a folder for the files and then select the proper sub package based on the OutputVariableName using a precedence constraint. I'm not sure how to write the expression to set the variable correctly. I want to set it based on a FINDSTRING() in the file name.
Your question is about how to use the File Watcher Task from Konesans in an integration services packages.
OutputVariableName String The name of the variable into which the full file path found will be written on completion of the task. The variable specified should be of type string
Via http://www.sqlis.com/post/file-watcher-task.aspx
Create an SSIS Variable at the Package level, called CurrentFileName. Configure the File Watcher Task such that the property OutputVariableName is User::CurrentFileName. When you drop a file into the folder that the Task is watching, it will assign the full path to that variable CurrentFileName.
Your desire is to do something with that Variable with FindString function to help determine the package to fire. Since you don't specify the something I'm going to assume it's based on file name.
It's a pity you're forcing a person to use FindString to perform this task. I say that because the .NET library offers an excellent static method to determine base file names and I hate seeing people re-invent (and debug) the wheel.
I would create 3 Variables to support this endeavor.
BaseFileName - String - Evaluate as Expression = True
FileExtensionPosition - Int32 - Evaluate as Expression = True
LastSlashPosition - Int32 - Evaluate as Expression = True
The LastSlashPosition is going to use FindString to determine the last occurrence of \ in a string. The FileExtensionPosition is going to determine the last occurence of . in a string. BaseFileName will use these numbers to calculate where to slice the #[User::CurrentFileName]` string.
The lazy trick I use for finding the last X in a string is to reverse it. It's then the first element in the string and I can pass 1 as the final parameter to FindString.
The expression assigned to #[User::LastSlashPosition] is
FINDSTRING(REVERSE(#[User::CurrentFileName]), "\\", 1)
The expression assigned to #[User::FileExtensionPosition] is
FINDSTRING(REVERSE(#[User::CurrentFileName]), ".", 1)
The expression assigned to #[User::BaseFileName] then becomes
SUBSTRING((RIGHT(#[User::CurrentFileName], #[User::LastSlashPosition] -1 )), 1, LEN(RIGHT( #[User::CurrentFileName], #[User::LastSlashPosition] -1)) - #[User::FileExtensionPosition] )
Breaking that down, (RIGHT(#[User::CurrentFileName], #[User::LastSlashPosition] -1 )) translates to the base file name. If CurrentFileName equals J:\ssisdata\so\FileWatcher\CleverFile.txt then that evaluates to "CleverFile.txt" I substring that to strip out the end. You can reduce this to just a single substring operation but my brain hurts this late.
Now you are trying to use, I assume, a series of Execute Package Tasks based on a Precedence Constraint of Success and #[User::BaseFilename] == "SubPackage1 You can do this and it'll work fine, it's just that you'll need to set each one up and as you go to set up a new child, you'll have to repeat the work.
As an alternative to this approach, I'd use a ForEach enumerator and define all my key value pairs in there.
Column 0 is the value that BaseFileName could evaluate to.
Column 1 is the SSIS package I want to fire off in response.
I created two variables to support this and configured them as such
My resulting package looks like
Not shown is the File Watcher Task because I have no desire to install that on my machine. Assume that connects to the ForEach Loop.
The ForEach loop spins through the key value pairs shown above. The Script Task inside the container is there just to provide a base for the Precedence Constraint to work. I configure the precedence constraint as Success and #[User::KeyName] == #[User::BaseFileName]
I then simulate the Execute Package Task firing based on that. The actual package name would be driven by the value of #[User::KeyPackage]
And that's your over-engineered solution for the day ;)
I make a tool with sqlalchemy that copies entries from one base to another. I want to add "dry run" option, so instead of real committing, it would just print a number of entries that would be committed:
session.add(foo)
session.add(bar)
if dry_run:
print session.number_of_items_to_commit # <-- should print "2"
else:
session.commit()
How to get the number of items that are to be committed? I didn't see any appropriate method in Session class.
You could probably use len(session.new) for your task:
The set of all instances marked as ‘new’ within this Session.
if you also need to track modified objects, use session.dirty
What does backpatching mean ? Please illustrate with a simple example.
Back patching usually refers to the process of resolving forward branches that have been planted in the code, e.g. at 'if' statements, when the value of the target becomes known, e.g. when the closing brace or matching 'else' is encountered.
In intermediate code generation stage of a compiler we often need to execute "jump" instructions to places in the code that don't exist yet. To deal with this type of cases a target label is inserted for that instruction.
A marker nonterminal in the production rule causes the semantic action to pick up.
Some statements like conditional statements, while, etc. will be represented as a bunch of "if" and "goto" syntax while generating the intermediate code.
The problem is that, These "goto" instructions, do not have a valid reference at the beginning(when the compiler starts reading the source code line by line - A.K.A 1st pass). But, after reading the whole source code for the first time, the labels and references these "goto"s are pointing to, are determined.
The problem is that can we make the compiler able to fill the X in the "goto X" statements in one single pass or not?
The answer is yes.
If we don't use backpatching, this can be achieved by a 2 pass analysis on the source code. But, backpatching lets us to create and hold a separate list which is exclusively designed for "goto" statements. Since it is done in only one pass, the first pass will not fill the X in the "goto X" statements because the comipler doesn't know where the X is at first glance. But, it does stores the X in that exclusive list and after going through the whole code and finding that X, the X is replaced by that address or reference.
Backpaching is the process of leaving blank entries for the goto instruction where the target address is unkonown in the forward transfer in the first pass and filling these unknown in the second pass.
Backpatching:
The syntax directed definition can be implemented in two or more passes (we have both synthesized attributes and inherited attributes).
Build the tree first.
Walk the tree in the depth-first order.
The main difficulty with code generation in one pass is that we may not know the target of a branch when we generate code for flow of control statements
Backpatching is the technique to get around this problem.
Generate branch instructions with empty targets
When the target is known, fill in the label of the branch instructions (backpatching).
backpatching is a process in which the operand field of an instruction containing a forward reference is left blank initially. the address of the forward reference symbol is put into this field when its definition is encountered in the program.
Back patching is the activity of filling up the unspecified information of labels
by using the appropriate semantic expression in during the code generation process.
It is done by:
boolean expression.
flow of control statement.