Matching multiple hex characters in a PGSQL Regex - regex

I'm trying to find some very specific multibyte characters in PostgreSQL using Regex. I know I have the option to make a long CASE WHEN but i decided to check if there is a different way to finding these.
My current Regex looks like this E'\xf0\x9f\x98\x83'
This works pretty well, except that I would need to find all from \xf0\x9f\x98\x80 to \xf0\x9f\x98\x99.
In JS I would just be able to write something like \xf0\x9f\x98[\x80-\x89] but for whatever reason this returns an error in PGSQL. Is there a shortcut like this, or am I doomed to writing 20 CASE WHEN-s?


I have realized my mistake. PGSQL Error was caused because I'm looking for 4 byte characters and I just wanted to mess with the last byte. I realized I'd have to write it like this: E'[\xf0\x9f\x98\x80-\xf0\x9f\x98\x90]'

Related

UTF-8 Encoding Regex

Hello I am bumping my head against the wall with Reg Expressions and UTF-8, I would like to filter emails that in the header from field comes with something like this:
=?UTF-8?Q?**FirstName**=C2=A0**LastName**?=
I want to be able to check first name and last name whether is in upper case, lower case, capitalized, etc.
I currently have a regex like this one \bFirstName+([ ])+LastName\b and that works like a charm, but when the header has UTF-8 Encoding does not work.

This isn't "UTF-8 encoding", it's MIME header encoding (using Quoted-Printable). There's only one reasonable way to deal with it: decode it (using an appropriate library for your language, probably found in an email-related package), and run your regex on the decoded result. Trying to match without decoding first, while not actually impossible, will be stupidly complex and error-prone.

Regex-Match while ignoring a char from Searchword

I am using an Engineering Program which lets me Code formulas in order to filter out specific lines in a database. I am trying to look for a certain line in the database which contains e.g. "concrete" as a property.
In the Code I can use regular expressions.
The regex I was using so far looked like this:
".*(concrete).*";
so if the line in the database contains concrete, I will get the wanted result.
Now the Problem is: i would like to switch the word concrete with a variable, so that it Looks like this:
".*(#VARIABLE1).*";
(the Syntax with the # works in the program btw.)
the Problem is: if i set the variable as concrete, the program automatically switches it for 'concrete' . Obviously, the word concrete cant be found anymore, since the searchterm now contains the two ' Symbols in the beginning and i the end.
Is there a way to ignore those two characters using the Right regex?
what I want it to do is the following:
If a line in the database contains "25cm concrete in Grey"
I should get a match from the regex.
with the searchterm ".*(concrete).*"; it works, with the variable ".*(#VARIABLE1).*"; it doesnt.
EDIT:
the whole "Formula" in the program Looks like that:
if(Match(QTO(Typ:="Attribut{FloorsLayer_02_MaterialName}");".*(#V_QUALITY).*" ;"regex") ;QTO(Typ:="Attribut{Fläche}");0)
I want the if-condition to be true, when the match inside is true.
the whole QTO function is just the programs Syntax to use a certain Attribute into the match-function, the middle part is my Problem. I really don't know the programming language or anything,I'm new to this. hope it helps!

Thats more of a hack than a real solution and i'm not sure if it even works:
if you use the regex
.*(#VARIABLE1)?).*
and the string ?concrete(
this will result in a regex looking like this:
.*('?concrete(')?).*
which makes the additional characters optional.
This uses the following assumtption:
the string (#VARIABLE1) gets replaced by the ('<content of VARIABLE1>')

Specific Regex Failing on Neko and Native

So I'm working on some cleanup in haxeflixel, and I need to validate a csv map, so I'm using a regex to check if its ok (don't mention the ending commas, I know thats not valid csv but I want to allow it), and I think I have a decent regex for doing that, and it seems to work well on flash, but c++ crashes, and neko gives me this error: An error occured while running pcre_exec....
here is my regex, I'm sorry its long, but I have no idea where the problem is...
^(([ ]*-?[0-9]+[ ]*,?)+\r?\n?)+$
if anyone knows what might be going on I'd appreciate it,
Thanks,
Nico
ps. there are probably errors in my regex for checking csv, but I can figure those out, its kind of enjoyable, I'd rather just know what specifically could be causing this:)
edit: ah, I've just noticed this doesn't happen on all strings, once I narrow it down to what strings, I will post one... as for what I'm checking for, its basically just to make sure theres no weird xml header, or any non integer value in the map file, basically it should validate this:
1,1,1,1
1,1,1,1
1,1,1,1
or this:
1,1,1,1,
1,1,1,1,
1,1,1,1,
but not:
xml blahh blahh>
1,m,1,1
1,1,b,1
1,1,1,1
xml>
(and yes I know thats not valid xml;))
edit: it gets stranger:
so I'm trying to determine what strings crash it, and while this still wouldnt explain a normal map crashing, its definatly weird, and has the same result:
what happens is:
this will fail a .match() test, but not crash:
a
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
while this will crash the program:
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1,*a*,1,1,1,1,1,1,1,1,1,1,1,1,1

To be honest, you wrote one of the worst regexps I ever seen. It actually looks like it was written specifically to be as slow as possible. I write it not to offend you, but to express how much you need to learn to write regexps(hint: writing your own regexp engine is a good exercise).
Going to your problem, I guess it just runs out of memory(it is extremely memory intensive). I am not sure why it happens only on pcre targets(both neko and cpp targets use pcre), but I guess it is about memory limits per regexp run in pcre or some heuristics in other targets to correct such miswritten regexps.
I'd suggest something along the lines of
~/^(( *-?[0-9]+ *,)* *-?[0-9]+ *,?\r?\n)*(( *-?[0-9]+ *,)* *-?[0-9]+ *,?\r?\n?)$/
There, "~/" and last "/" are haxe regexp markers.
I wasnt extensively testing it, just a run on your samples, but it should do the job(probably with a bit of tweaking).
Also, just as a hint, I'd suggest you to split file into lines first before running any regexps, it will lower memmory usage(or you will need to hold only a part of your text in memory) and simplify your regexp.
I'd also note that since you will need to parse csv anyhow(for any properly formed input, which are prevailing in your data I guess), it might be much faster to do all the tests while actually parsing.
Edit: the answer to question "why it eats so much memory"
Well, it is not a short topic, and that's why I proposed to you to write your own regexp engine. There are some differences in implementations, but generally imagine regexp engine works like that:
parses your regular expression and builds a graph of all possible states(state is basically a symbol value and a number of links to other symbols which can follow it).
sets up a list of read pointer and state pointer pairs, current state list, consisting of regexp initial state and a pointer to matched string first letter
sets up read pointer to the first symbol of symbol string
sets up state poiter to initial state of regexp
takes up one pair from current state list and stores it as current state and current read pointer
reads symbol under current read pointer
matches it with symbols in states which current state have links to, and makes a list of states that matched.
if there is a final regexp state in this list, goes to 12
for each item in this list adds a pair of next read pointer(which is current+1) and item to the current state list
if the current state list is empty, returns false, as string didn't match the regexp
goes to 6
here it is, in a final state of matched regexp, returns true, string matches regexp.
Of course, there are some differences between regexp engines, and some of them eliminate some problems afaik. And of course they also have pseudosymbols, groupings, they need to store the positions regexp and groups matched, they have lookahead and lookbehind and also grouping references which makes it a bit(quite a humble measure) more complex and forces to use a bit more complex data structures, but the main idea is the same. So, here we are and your problem is clearly seen from algorithm. The less specific you are about what you want to match and the more there chances for engine to match the same substring as different paths in state graph, the more memory and processor time it will consume, exponentionally.
Try to model how regexp engine matches regexp (a+a+)+b on strings aaaaaab, ab, aa, aaaaaaaaaa, aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (Don't try the last one, it would take hours or days to compute on a modern PC.)
Also, it worth to note that some regexp engines do things in a bit different way so they can handle this situations properly, but there always are ways to make regexp extremely slow.
And another thing to note is that I may hav ebeen wrong about the exact memory problem. This case it may be processor too, and before that it may be engine limits on memory/processor kicking in, not exactly system starving of memory.

Using Regex to validate the number of words in a text area

I am attempting to write a MVC model validation that verifies that there is 10 or more words in a string. The string is being populated correctly, so I did not include the HTML. I have done a fair bit of research, and it seems that something along the lines of what I have tries should work, but, for whatever reason, mine always seem to fail. Any ideas as to what I am doing wrong here?
(using System.ComponentModel.DataAnnotations, in a mvc 4 vb.net environment)
Have tried ([\w]+){10,}, ((\\S+)\s?){10,}, [\b]{20,}, [\w+\w?]{10,}, (\b(\w+?)\b){10,}, ([\w]+?\s){10}, ([\w]+?\s){9}[\w], ([\S]+\s){9}[\S], ([a-zA-Z0-9,.'":;$-]+\s+){10,} and several more varaiations on the same basic idea.
<Required(ErrorMessage:="The Description of Operations field is required"), RegularExpression("([\w]+){20,}", ErrorMessage:="ERROZ")>
Public Property DescOfOperations As String = String.Empty
Correct Solution was ([\S]+\s+){9}[\S\s]+

EDIT Moved accepted version to the top, removing unused versions. Unless I am wrong and the whole sequence needs to match, then something like (also accounting for double spaces):
([\S]+\s+){9}[\S\s]+
Or:
([\w]+?\s+){9}[\w]+

Give this a try:
([a-zA-Z0-9,.'":;$-]+\s){10,}

Find Lines with N occurrences of a char

I have a txt file that I’m trying to import as flat file into SQL2008 that looks like this:
“123456”,”some text”
“543210”,”some more text”
“111223”,”other text”
etc…
The file has more than 300.000 rows and the text is large (usually 200-500 chars), so scanning the file by hand is very time consuming and prone to error. Other similar (and even more complex files) were successfully imported.
The problem with this one, is that “some lines” contain quotes in the text… (this came from an export from an old SuperBase DB that didn’t let you specify a text quantifier, there’s nothing I can do with the file other than clear it and try to import it).
So the “offending” lines look like this:
“123456”,”this text “contains” a quote”
“543210”,”And the “above” text is bad”
etc…
You can see the problem here.
Now, 300.000 is not too much if I could perform a search using a text editor that can use regex, I’d manually remove the quotes from each line. The problem is not the number of offending lines, but the impossibility to find them with a simple search. I’m sure there are less than 500, but spread those in a 300.000 lines txt file and you know what I mean.
Based upon that, what would be the best regex I could use to identify these lines?
My first thought is: Tell me which lines contain more than 4 quotes (“).
But I couldn’t come up with anything (I’m not good at Regex beyond the basics).

this pattern ^("[^"]+){4,} will match "lines containing more than 4 quotes"
you can experiment with replacing 4 with 5 or more, depending on your data.

I think that you can be more direct with a Regex than you're planning to be. Depending on your dialect of Regex, something like this should do it:
^"\d+",".*".*"

You could also use a regex to remove the outside quotes and use a better delimeter instead. For example, search for ^"([0-9]+)","(.*)"$ and replace it with \1+++++DELIM+++++\2.
Of course, this doesn't directly answer your question, but it might solve the problem.