January 2021 - Pharo-users - lists.pharo.org

[ANN] Stargate-Consul v2.0.0 [v2.0.0] released!

by Buenos Aires Smalltalk

Jan. 6, 2021

[ANN] Superluminal v1.2.1 [v1.2.1] released!

by Buenos Aires Smalltalk

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by Sven Van Caekenberghe

Joachim, > On 6 Jan 2021, at 11:21, jtuchel(a)objektfabrik.de wrote: > > Hi Sven, > > > I must say I am really happy with your change. We get a nice exception whenever the number of fieldAccessor doesn't match with the number of defined fieldAccessors. So far it also seems the endless loops are gone as well. What a leap forward! Thank you for your kind words. But thank you as well: it really helps to get constructive feedback from actual users, to improve the code for everyone. > I'm adding an issue on github about the conversion errors, I hope that is a convenient place for such comments/ideas? Did you see NeoCSVReaderTests>>#testConversionErrors ? It is not perfect, but you do get an error when a number conversion fails, you could make your own conversions fail similarly. (NeoCSVReader on: 'a' readStream) addIntegerField; upToEnd. Like you said: some validation can be done at the CSV level, but certainly not everything. Sven > Joachim > > > > > > > Am 05.01.21 um 21:06 schrieb jtuchel(a)objektfabrik.de: >> Sven, >> >> >> I tested your change with the file and filter (our own way of defining csv mappings by the end users) which used to send our application into an endless loop. >> >> And voila: we get an exception instead of a frozen image! I will give the conversion errors a test drive tomorrow. >> >> I am absolutely happy with your change. Thank you very much. >> >> >> Joachim >> >> >> P.S: I even learned a little bit about Iceberg. I am not really sure each of my mouse clicks made sense, but I had your commit in the image and could test it and port the deltas over to my Smalltalk dialect... >> >> >> >> >> >> >> >> Am 05.01.21 um 19:52 schrieb jtuchel(a)objektfabrik.de: >>> Hi Sven, >>> >>> >>> all I can say is: wow. I have no words. >>> >>> I will have to learn a bit about Pharo and github real quick now in order to try your changes.... >>> >>> Thank you very much. I'll give you feedback as fast as I can. >>> >>> (And forget my questions about #readAtEndOrEndOfLine. I somhow didn't understand it is expected to return a Boolean. Not sure why. I thought of 'read' as a command, not a question in simple past..., so I thought its job should be to read the rest of the line if we're not there yet) >>> >>> >>> Joachim >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> Am 05.01.21 um 17:49 schrieb Sven Van Caekenberghe: >>>> Hi Joachim, >>>> >>>> Have a look at the following commit: >>>> >>>> https://github.com/svenvc/NeoCSV/commit/a3d6258c28138fe3b15aa03ae71cf1e0770… >>>> >>>> and specifically the added unit tests. These should help clarify the new behaviour. >>>> >>>> If anything is not clear, please ask. >>>> >>>> HTH, >>>> >>>> Sven >>>> >>>>> On 5 Jan 2021, at 08:49, jtuchel(a)objektfabrik.de wrote: >>>>> >>>>> Sven, >>>>> >>>>> first of all thanks a lot for taking your time with this! >>>>> >>>>> Your test case is so beautifully small I can't believe it ;-) >>>>> >>>>> While I think some kind of validation could help with parsing CSV, I remember reading your comment on this in some other discussion long ago. You wrote you don't see it as a responsibility of a parser and that you wouldn't want to add this to NeoCSV. I must say I tend to agree mostly. Whatever you do at parsing can only cover part of the problems related to validation. There will be checks that require access to other fields from the same line, or some object that will be the owner of the Collection that you are just importing, so a lot of validation must be done after parsing anyways. >>>>> >>>>> So I think we can mostly ignore the validation part. Whatever a reader will do, it will not be good enough. >>>>> >>>>> A nice way of exposing conversion errors for fields created with #addField:converter: would help a lot, however. >>>>> >>>>> I am glad you agree on the underflow bug. This is more a question of well-formedness than of validation. If a reader finds out it doesn't fit for a file structure, it should tell the user/developer about it or at least gracefully return some more or less incomplete object resembling what it could parse. But it shouldn't cross line borders and return a wrong number of objects. >>>>> >>>>> >>>>> I will definitely continue my hunt for the endless loop. It is not an ideal situation if one user of our Seaside Application completely blocks an image that may be serving a few other users by just using a CVS parser that doesn't fit with the file. I suspect this has to do with #readEndOfLine in some special case of the underflow bug, but cannot prove it yet. But I have a file and parser that reliably goes into an endless loop. I just need to isolate the bare CSV parsing from the whole machinery we've build around NeoCSV reader for these user-defined mappings... I wouldn't be surprised if it is a problem buried somewhere in our preparations in building a parser from user-defined data... I will report my progress here, I promise! >>>>> >>>>> >>>>> One question I keep thinking about in NeoCSV: You implemented a method called #peekChar, but it doesn't #peek. It buffers a character and does read the #next character. I tried replacing the #next with #peek, but that is definitely a shortcut to 100% CPU, because #peekChar is used a lot, not only for consuming an "unmapped remainder" of a line... I somehow have the feeling that at least in #readEndOfLine the next char should bee peeked instead of consumed in order to find out if it's workload or part of the crlf/lf... >>>>> Shouldn't a reader step forward by using #peek to see whether there is more data after all fieldAccessors have been applied to the line (see #readNextRecordAsObject)? Otoh, at one point the reader has to skip to the next line, so I am not sure if peek has any place here... I need to debug a little more to understand... >>>>> >>>>> >>>>> >>>>> Joachim >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> Am 04.01.21 um 20:57 schrieb Sven Van Caekenberghe: >>>>>> Hi Joachim, >>>>>> >>>>>> Thanks for the detailed feedback. This is most helpful. I need to think more about this and experiment a bit. This is what I came up with in a Workspace/Playground: >>>>>> >>>>>> input := 'foo,1 >>>>>> bar,2 >>>>>> foobar,3'. >>>>>> >>>>>> (NeoCSVReader on: input readStream) upToEnd. >>>>>> (NeoCSVReader on: input readStream) addField; upToEnd. >>>>>> (NeoCSVReader on: input readStream) addField; addField; addField; upToEnd. >>>>>> >>>>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; addField: [ :obj :str | obj at: #one put: str]; upToEnd. >>>>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; addField: [ :obj :str | obj at: #one put: str]; addField: [ :obj :str | obj at: #two put: str]; addField: [ :obj :str | obj at: #three put: str]; upToEnd. >>>>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; emptyFieldValue: #passNil; addField: [ :obj :str | obj at: #one put: str]; addField: [ :obj :str | obj at: #two put: str]; addField: [ :obj :str | obj at: #three put: str]; upToEnd. >>>>>> >>>>>> In my opinion there are two distinct issues: >>>>>> >>>>>> 1. what to do when you define a specific number of fields to be read and there are not enough of them in the input (underflow), or there are too many of them in the input (overflow). >>>>>> >>>>>> it is clear that the underflow case is wrong and a bug that has to be fixed. >>>>>> the overflow case seems OK (resulting in nil fields) >>>>>> >>>>>> 2. to validate the input (a functionality not yet present) >>>>>> >>>>>> this would basically mean to signal an error in the under or overflow case. >>>>>> but wrong type conversions should be errors too. >>>>>> >>>>>> I understand that you want to validate foreign input. >>>>>> >>>>>> It is a pity that you cannot produce an infinite loop example, that would also be useful. >>>>>> >>>>>> That's it for now, I will come back to you. >>>>>> >>>>>> Regards, >>>>>> >>>>>> Sven >>>>>> >>>>>>> On 4 Jan 2021, at 14:46, jtuchel(a)objektfabrik.de wrote: >>>>>>> >>>>>>> Please find attached a small test case to demonstrate what I mean. There is just some nonsense Business Object class and a simple test case in this fileout. >>>>>>> >>>>>>> >>>>>>> Am 04.01.21 um 14:36 schrieb jtuchel(a)objektfabrik.de: >>>>>>>> Happy new year to all of you! May 2021 be an increasingly less crazy year than 2020... >>>>>>>> >>>>>>>> >>>>>>>> I have a question that sounds a bit strange, but we have two effects with NeoCSVReader related to wrong definitions of the reader. >>>>>>>> >>>>>>>> One effect is that reading a Stream #upToEnd leads to an endless loop, the other is that the Reader produces twice as many objects as there are lines in the file that is being read. >>>>>>>> >>>>>>>> In both scenarios, the reason is that the CSV Reader has a wrong number of column definitions. >>>>>>>> >>>>>>>> Of course that is my fault: why do I feed a "malformed" CSV file to poor NeoCSVReader? >>>>>>>> >>>>>>>> Let me explain: we have a few import interfaces which end users can define using a more or less nice assistant in our Application. The CSV files they upload to our App come from third parties like payment providers, banks and other sources. These change their file structures whenever they feel like it and never tell anybody. So a CSV import that may have been working for years may one day tear a whole web server image down because of a wrong number of fieldAccessors. This is bad on many levels. >>>>>>>> >>>>>>>> You can easily try the doubling effect at home: define a working CSV Reader and comment out one of the addField: commands before you use the NeoCSVReader to parse a CSV file. Say your CSV file has 3 lines with 4 columns each. If you remove one of the fieldAccessors, an #upToEnd will yoield an Array of 6 objects rather than 3. >>>>>>>> >>>>>>>> I haven't found the reason for the cases where this leads to an endless loop, but at least this one is clear... >>>>>>>> >>>>>>>> I *guess* this is due to the way #readEndOfLine is implemented. It seems to not peek forward to the end of the line. I have the gut feeling #peekChar should peek instead of reading the #next character form the input Stream, but #peekChar has too many senders to just go ahead and mess with it ;-) >>>>>>>> >>>>>>>> So I wonder if there are any tried approaches to this problem. >>>>>>>> >>>>>>>> One thing I might do is not use #upToEnd, but read each line using PositionableStream>>#nextLine and first check each line if the number of separators matches the number of fieldAccessors minus 1 (and go through the hoops of handling separators in quoted fields and such...). Only if that test succeeds, I would then hand a Stream with the whole line to the reader and do a #next. >>>>>>>> >>>>>>>> This will, however, mean a lot of extra cycles for large files. Of course I could do this only for some lines, maybe just the first one. Whatever. >>>>>>>> >>>>>>>> >>>>>>>> But somehow I have the feeling I should get an exception telling me the line is not compatible to the Reader's definition or such. Or #readAtEndOrEndOfLine should just walk the line to the end and ignore the rest of the line, returnong an incomplete object.... >>>>>>>> >>>>>>>> >>>>>>>> Maybe I am just missing the right setting or switch? What best practices did you guys come up with for such problems? >>>>>>>> >>>>>>>> >>>>>>>> Thanks in advance, >>>>>>>> >>>>>>>> >>>>>>>> Joachim >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> -- >>>>>>> ----------------------------------------------------------------------- >>>>>>> Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de >>>>>>> Fliederweg 1 http://www.objektfabrik.de >>>>>>> D-71640 Ludwigsburg http://joachimtuchel.wordpress.com >>>>>>> Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1 >>>>>>> >>>>>>> >>>>>>> <NeoCSVEndlessLoopTest.st> >>>>> >>>>> -- >>>>> ----------------------------------------------------------------------- >>>>> Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de >>>>> Fliederweg 1 http://www.objektfabrik.de >>>>> D-71640 Ludwigsburg http://joachimtuchel.wordpress.com >>>>> Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1 >>>>> >>> >> > > -- > ----------------------------------------------------------------------- > Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de > Fliederweg 1 http://www.objektfabrik.de > D-71640 Ludwigsburg http://joachimtuchel.wordpress.com > Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1 >

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by jtuchel＠objektfabrik.de

Hi Sven, I must say I am really happy with your change. We get a nice exception whenever the number of fieldAccessor doesn't match with the number of defined fieldAccessors. So far it also seems the endless loops are gone as well. What a leap forward! I'm adding an issue on github about the conversion errors, I hope that is a convenient place for such comments/ideas? Joachim Am 05.01.21 um 21:06 schrieb jtuchel(a)objektfabrik.de: > Sven, > > > I tested your change with the file and filter (our own way of defining > csv mappings by the end users) which used to send our application into > an endless loop. > > And voila: we get an exception instead of a frozen image! I will give > the conversion errors a test drive tomorrow. > > I am absolutely happy with your change. Thank you very much. > > > Joachim > > > P.S: I even learned a little bit about Iceberg. I am not really sure > each of my mouse clicks made sense, but I had your commit in the image > and could test it and port the deltas over to my Smalltalk dialect... > > > > > > > > Am 05.01.21 um 19:52 schrieb jtuchel(a)objektfabrik.de: >> Hi Sven, >> >> >> all I can say is: wow. I have no words. >> >> I will have to learn a bit about Pharo and github real quick now in >> order to try your changes.... >> >> Thank you very much. I'll give you feedback as fast as I can. >> >> (And forget my questions about #readAtEndOrEndOfLine. I somhow didn't >> understand it is expected to return a Boolean. Not sure why. I >> thought of 'read' as a command, not a question in simple past..., so >> I thought its job should be to read the rest of the line if we're not >> there yet) >> >> >> Joachim >> >> >> >> >> >> >> >> >> >> Am 05.01.21 um 17:49 schrieb Sven Van Caekenberghe: >>> Hi Joachim, >>> >>> Have a look at the following commit: >>> >>> https://github.com/svenvc/NeoCSV/commit/a3d6258c28138fe3b15aa03ae71cf1e0770… >>> >>> >>> and specifically the added unit tests. These should help clarify the >>> new behaviour. >>> >>> If anything is not clear, please ask. >>> >>> HTH, >>> >>> Sven >>> >>>> On 5 Jan 2021, at 08:49, jtuchel(a)objektfabrik.de wrote: >>>> >>>> Sven, >>>> >>>> first of all thanks a lot for taking your time with this! >>>> >>>> Your test case is so beautifully small I can't believe it ;-) >>>> >>>> While I think some kind of validation could help with parsing CSV, >>>> I remember reading your comment on this in some other discussion >>>> long ago. You wrote you don't see it as a responsibility of a >>>> parser and that you wouldn't want to add this to NeoCSV. I must say >>>> I tend to agree mostly. Whatever you do at parsing can only cover >>>> part of the problems related to validation. There will be checks >>>> that require access to other fields from the same line, or some >>>> object that will be the owner of the Collection that you are just >>>> importing, so a lot of validation must be done after parsing anyways. >>>> >>>> So I think we can mostly ignore the validation part. Whatever a >>>> reader will do, it will not be good enough. >>>> >>>> A nice way of exposing conversion errors for fields created with >>>> #addField:converter: would help a lot, however. >>>> >>>> I am glad you agree on the underflow bug. This is more a question >>>> of well-formedness than of validation. If a reader finds out it >>>> doesn't fit for a file structure, it should tell the user/developer >>>> about it or at least gracefully return some more or less incomplete >>>> object resembling what it could parse. But it shouldn't cross line >>>> borders and return a wrong number of objects. >>>> >>>> >>>> I will definitely continue my hunt for the endless loop. It is not >>>> an ideal situation if one user of our Seaside Application >>>> completely blocks an image that may be serving a few other users by >>>> just using a CVS parser that doesn't fit with the file. I suspect >>>> this has to do with #readEndOfLine in some special case of the >>>> underflow bug, but cannot prove it yet. But I have a file and >>>> parser that reliably goes into an endless loop. I just need to >>>> isolate the bare CSV parsing from the whole machinery we've build >>>> around NeoCSV reader for these user-defined mappings... I wouldn't >>>> be surprised if it is a problem buried somewhere in our >>>> preparations in building a parser from user-defined data... I will >>>> report my progress here, I promise! >>>> >>>> >>>> One question I keep thinking about in NeoCSV: You implemented a >>>> method called #peekChar, but it doesn't #peek. It buffers a >>>> character and does read the #next character. I tried replacing the >>>> #next with #peek, but that is definitely a shortcut to 100% CPU, >>>> because #peekChar is used a lot, not only for consuming an >>>> "unmapped remainder" of a line... I somehow have the feeling that >>>> at least in #readEndOfLine the next char should bee peeked instead >>>> of consumed in order to find out if it's workload or part of the >>>> crlf/lf... >>>> Shouldn't a reader step forward by using #peek to see whether there >>>> is more data after all fieldAccessors have been applied to the line >>>> (see #readNextRecordAsObject)? Otoh, at one point the reader has to >>>> skip to the next line, so I am not sure if peek has any place >>>> here... I need to debug a little more to understand... >>>> >>>> >>>> >>>> Joachim >>>> >>>> >>>> >>>> >>>> >>>> >>>> Am 04.01.21 um 20:57 schrieb Sven Van Caekenberghe: >>>>> Hi Joachim, >>>>> >>>>> Thanks for the detailed feedback. This is most helpful. I need to >>>>> think more about this and experiment a bit. This is what I came up >>>>> with in a Workspace/Playground: >>>>> >>>>> input := 'foo,1 >>>>> bar,2 >>>>> foobar,3'. >>>>> >>>>> (NeoCSVReader on: input readStream) upToEnd. >>>>> (NeoCSVReader on: input readStream) addField; upToEnd. >>>>> (NeoCSVReader on: input readStream) addField; addField; addField; >>>>> upToEnd. >>>>> >>>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; >>>>> addField: [ :obj :str | obj at: #one put: str]; upToEnd. >>>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; >>>>> addField: [ :obj :str | obj at: #one put: str]; addField: [ :obj >>>>> :str | obj at: #two put: str]; addField: [ :obj :str | obj at: >>>>> #three put: str]; upToEnd. >>>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; >>>>> emptyFieldValue: #passNil; addField: [ :obj :str | obj at: #one >>>>> put: str]; addField: [ :obj :str | obj at: #two put: str]; >>>>> addField: [ :obj :str | obj at: #three put: str]; upToEnd. >>>>> >>>>> In my opinion there are two distinct issues: >>>>> >>>>> 1. what to do when you define a specific number of fields to be >>>>> read and there are not enough of them in the input (underflow), or >>>>> there are too many of them in the input (overflow). >>>>> >>>>> it is clear that the underflow case is wrong and a bug that has to >>>>> be fixed. >>>>> the overflow case seems OK (resulting in nil fields) >>>>> >>>>> 2. to validate the input (a functionality not yet present) >>>>> >>>>> this would basically mean to signal an error in the under or >>>>> overflow case. >>>>> but wrong type conversions should be errors too. >>>>> >>>>> I understand that you want to validate foreign input. >>>>> >>>>> It is a pity that you cannot produce an infinite loop example, >>>>> that would also be useful. >>>>> >>>>> That's it for now, I will come back to you. >>>>> >>>>> Regards, >>>>> >>>>> Sven >>>>> >>>>>> On 4 Jan 2021, at 14:46, jtuchel(a)objektfabrik.de wrote: >>>>>> >>>>>> Please find attached a small test case to demonstrate what I >>>>>> mean. There is just some nonsense Business Object class and a >>>>>> simple test case in this fileout. >>>>>> >>>>>> >>>>>> Am 04.01.21 um 14:36 schrieb jtuchel(a)objektfabrik.de: >>>>>>> Happy new year to all of you! May 2021 be an increasingly less >>>>>>> crazy year than 2020... >>>>>>> >>>>>>> >>>>>>> I have a question that sounds a bit strange, but we have two >>>>>>> effects with NeoCSVReader related to wrong definitions of the >>>>>>> reader. >>>>>>> >>>>>>> One effect is that reading a Stream #upToEnd leads to an endless >>>>>>> loop, the other is that the Reader produces twice as many >>>>>>> objects as there are lines in the file that is being read. >>>>>>> >>>>>>> In both scenarios, the reason is that the CSV Reader has a wrong >>>>>>> number of column definitions. >>>>>>> >>>>>>> Of course that is my fault: why do I feed a "malformed" CSV file >>>>>>> to poor NeoCSVReader? >>>>>>> >>>>>>> Let me explain: we have a few import interfaces which end users >>>>>>> can define using a more or less nice assistant in our >>>>>>> Application. The CSV files they upload to our App come from >>>>>>> third parties like payment providers, banks and other sources. >>>>>>> These change their file structures whenever they feel like it >>>>>>> and never tell anybody. So a CSV import that may have been >>>>>>> working for years may one day tear a whole web server image down >>>>>>> because of a wrong number of fieldAccessors. This is bad on many >>>>>>> levels. >>>>>>> >>>>>>> You can easily try the doubling effect at home: define a working >>>>>>> CSV Reader and comment out one of the addField: commands before >>>>>>> you use the NeoCSVReader to parse a CSV file. Say your CSV file >>>>>>> has 3 lines with 4 columns each. If you remove one of the >>>>>>> fieldAccessors, an #upToEnd will yoield an Array of 6 objects >>>>>>> rather than 3. >>>>>>> >>>>>>> I haven't found the reason for the cases where this leads to an >>>>>>> endless loop, but at least this one is clear... >>>>>>> >>>>>>> I *guess* this is due to the way #readEndOfLine is implemented. >>>>>>> It seems to not peek forward to the end of the line. I have the >>>>>>> gut feeling #peekChar should peek instead of reading the #next >>>>>>> character form the input Stream, but #peekChar has too many >>>>>>> senders to just go ahead and mess with it ;-) >>>>>>> >>>>>>> So I wonder if there are any tried approaches to this problem. >>>>>>> >>>>>>> One thing I might do is not use #upToEnd, but read each line >>>>>>> using PositionableStream>>#nextLine and first check each line if >>>>>>> the number of separators matches the number of fieldAccessors >>>>>>> minus 1 (and go through the hoops of handling separators in >>>>>>> quoted fields and such...). Only if that test succeeds, I would >>>>>>> then hand a Stream with the whole line to the reader and do a >>>>>>> #next. >>>>>>> >>>>>>> This will, however, mean a lot of extra cycles for large files. >>>>>>> Of course I could do this only for some lines, maybe just the >>>>>>> first one. Whatever. >>>>>>> >>>>>>> >>>>>>> But somehow I have the feeling I should get an exception telling >>>>>>> me the line is not compatible to the Reader's definition or >>>>>>> such. Or #readAtEndOrEndOfLine should just walk the line to the >>>>>>> end and ignore the rest of the line, returnong an incomplete >>>>>>> object.... >>>>>>> >>>>>>> >>>>>>> Maybe I am just missing the right setting or switch? What best >>>>>>> practices did you guys come up with for such problems? >>>>>>> >>>>>>> >>>>>>> Thanks in advance, >>>>>>> >>>>>>> >>>>>>> Joachim >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> -- >>>>>> ----------------------------------------------------------------------- >>>>>> >>>>>> Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de >>>>>> Fliederweg 1 http://www.objektfabrik.de >>>>>> D-71640 Ludwigsburg http://joachimtuchel.wordpress.com >>>>>> Telefon: +49 7141 56 10 86 0Â Â Â Â Â Â Â Â Fax: +49 7141 56 10 86 1 >>>>>> >>>>>> >>>>>> <NeoCSVEndlessLoopTest.st> >>>> >>>> -- >>>> ----------------------------------------------------------------------- >>>> >>>> Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de >>>> Fliederweg 1 http://www.objektfabrik.de >>>> D-71640 Ludwigsburg http://joachimtuchel.wordpress.com >>>> Telefon: +49 7141 56 10 86 0Â Â Â Â Â Â Â Â Fax: +49 7141 56 10 86 1 >>>> >> > -- ----------------------------------------------------------------------- Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de Fliederweg 1 http://www.objektfabrik.de D-71640 Ludwigsburg http://joachimtuchel.wordpress.com Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by Sven Van Caekenberghe

Hi Richard, Benchmarking is a can of worms, many factors have to be considered. But the first requirement is obviously to be completely open over what you are doing and what you are comparing. NeoCSV contains a simple benchmark suite called NeoCSVBenchmark, which was used during development. Note that it is a bit tricky to use: you need to run a write benchmark with a specific configuration before you can try read benchmarks. The core data is a 100.000 line file (2.5 MB) like this: 1,-1,99999 2,-2,99998 3,-3,99997 4,-4,99996 5,-5,99995 6,-6,99994 7,-7,99993 8,-8,99992 9,-9,99991 10,-10,99990 ... That parses in ~250ms on my machine. NeoCSV has quite a bit of features and handles various edge cases. Obviously, a minimal, custom implementation could be faster. NeoCSV is called efficient not just because it is reasonably fast, but because it can be configured to generate domain objects without intermediate structures and because it can convert individual fields (parse numbers, dates, times, ...) while parsing. Like you said, some generated CSV output out in the wild is very irregular. I try to stick with standard CSV as much as possible. Sven > On 6 Jan 2021, at 05:10, Richard O'Keefe <raoknz(a)gmail.com> wrote: > > NeoCSVReader is described as efficient. What is that > in comparison to? What benchmark data are used? > Here are benchmark results measured today. > (5,000 data line file, 9,145,009 characters). > method time(ms) > Just read characters 410 > CSVDecoder>>next 3415 astc's CSV reader (defaults). 1.26 x CSVParser > NeoCSVReader>>next 4798 NeoCSVReader (default state). 1.78 x CSVParser > CSVParser>>next 2701 pared-to-the-bone CSV reader. 1.00 reference. > > (10,000 data line file, 1,544,836 characters). > method time(ms) > Just read characters 93 > CSVDecoder>>next 530 astc's CSV reader (defaults). 1.26 x CSVParser > NeoCSVReader>>next 737 NeoCSVReader (default state). 1.75 x CSVParser > CSVParser>>next 421 pared-to-the-bone CSV reader. 1.00 reference. > > CSVParser is just 78 lines and is not customisable. It really is > stripped to pretty much an absolute minimum. All of the parsers > were configured (if that made sense) to return an Array of Strings. > Many of the CSV files I've worked with use short records instead > of ending a line with a lot of commas. Some of them also have the occasional stray comment off to the right, not mentioned in the header. > I've also found it necessary to skip multiple lines at the beginning > and/or end. (Really, some government agencies seem to have NO idea > that anyone might want to do more with a CSV file than eyeball it in > Excel.) > > If there is a benchmark suite I can use to improve CSVDecoder, > I would like to try it out. > > On Tue, 5 Jan 2021 at 02:36, jtuchel(a)objektfabrik.de <jtuchel(a)objektfabrik.de> wrote: > Happy new year to all of you! May 2021 be an increasingly less crazy > year than 2020... > > > I have a question that sounds a bit strange, but we have two effects > with NeoCSVReader related to wrong definitions of the reader. > > One effect is that reading a Stream #upToEnd leads to an endless loop, > the other is that the Reader produces twice as many objects as there are > lines in the file that is being read. > > In both scenarios, the reason is that the CSV Reader has a wrong number > of column definitions. > > Of course that is my fault: why do I feed a "malformed" CSV file to poor > NeoCSVReader? > > Let me explain: we have a few import interfaces which end users can > define using a more or less nice assistant in our Application. The CSV > files they upload to our App come from third parties like payment > providers, banks and other sources. These change their file structures > whenever they feel like it and never tell anybody. So a CSV import that > may have been working for years may one day tear a whole web server > image down because of a wrong number of fieldAccessors. This is bad on > many levels. > > You can easily try the doubling effect at home: define a working CSV > Reader and comment out one of the addField: commands before you use the > NeoCSVReader to parse a CSV file. Say your CSV file has 3 lines with 4 > columns each. If you remove one of the fieldAccessors, an #upToEnd will > yoield an Array of 6 objects rather than 3. > > I haven't found the reason for the cases where this leads to an endless > loop, but at least this one is clear... > > I *guess* this is due to the way #readEndOfLine is implemented. It seems > to not peek forward to the end of the line. I have the gut feeling > #peekChar should peek instead of reading the #next character form the > input Stream, but #peekChar has too many senders to just go ahead and > mess with it ;-) > > So I wonder if there are any tried approaches to this problem. > > One thing I might do is not use #upToEnd, but read each line using > PositionableStream>>#nextLine and first check each line if the number of > separators matches the number of fieldAccessors minus 1 (and go through > the hoops of handling separators in quoted fields and such...). Only if > that test succeeds, I would then hand a Stream with the whole line to > the reader and do a #next. > > This will, however, mean a lot of extra cycles for large files. Of > course I could do this only for some lines, maybe just the first one. > Whatever. > > > But somehow I have the feeling I should get an exception telling me the > line is not compatible to the Reader's definition or such. Or > #readAtEndOrEndOfLine should just walk the line to the end and ignore > the rest of the line, returnong an incomplete object.... > > > Maybe I am just missing the right setting or switch? What best practices > did you guys come up with for such problems? > > > Thanks in advance, > > > Joachim > > > > > > > > > > > > > > > > > >

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by jtuchel＠objektfabrik.de

Richard, I am not sure what point you are trying to make here. You have something cooler and faster? Great, how about sharing? You could make a faster one when it doesn't convert numbers and stuff? Great. I guess the time will be spent after parsing in 95% of the use cases. It depends. And that is exactly what you are saying. The word efficient means nothing without context. How is that related to this thread? I think this thread mostly shows the strength of a community, especially when there are members who are active, friendly and highly motivated. My problem git solved in blazing speed without me paying anything for it. Just because Sven thought my problem could be other people's problem as well. I am happy with NeoCSV's speed, even if there may be more lightweigt and faster solutions. Tbh, my main concern with NeoCSV is not speed, but how well I can understand problems and fix them. I care about data types on parsing. A non-configurable csv parser gives me a bunch of dictionaries and Strings. That could be a waste of cycles and memory once you need the data as objects. My use case is not importing trillions of records all day, and for a few hundred or maybe sometimes thousands, it is good/fast enough. Joachim Am 06.01.21 um 05:10 schrieb Richard O'Keefe: > NeoCSVReader is described as efficient.Â What is that > in comparison to? What benchmark data are used? > Here are benchmark results measured today. > (5,000 data line file, 9,145,009 characters). > Â method Â Â Â Â Â Â Â Â time(ms) > Â Just read characters Â 410 > Â CSVDecoder>>next Â Â Â 3415 Â astc's CSV reader (defaults). 1.26 x > CSVParser > Â NeoCSVReader>>next Â Â 4798 Â NeoCSVReader (default state). 1.78 x > CSVParser > Â CSVParser>>next Â Â Â 2701 Â pared-to-the-bone CSV reader. 1.00 > reference. > > (10,000 data line file, 1,544,836 characters). > Â method Â Â Â Â Â Â Â Â time(ms) > Â Just read characters Â Â 93 > Â CSVDecoder>>next Â Â Â 530 Â astc's CSV reader (defaults). 1.26 x > CSVParser > Â NeoCSVReader>>next Â Â 737 Â NeoCSVReader (default state). 1.75 x > CSVParser > Â CSVParser>>next Â Â Â Â 421 Â pared-to-the-bone CSV reader. 1.00 > reference. > > CSVParser is just 78 lines and is not customisable.Â It really is > stripped to pretty much an absolute minimum.Â All of the parsers > were configured (if that made sense) to return an Array of Strings. > Many of the CSV files I've worked with use short records instead > of ending a line with a lot of commas.Â Some of them also have the > occasional stray comment off to the right, not mentioned in the header. > I've also found it necessary to skip multiple lines at the beginning > and/or end.Â (Really, some government agencies seem to have NO idea > that anyone might want to do more with a CSV file than eyeball it in > Excel.) > > If there is a benchmark suite I can use to improve CSVDecoder, > I would like to try it out. > > On Tue, 5 Jan 2021 at 02:36, jtuchel(a)objektfabrik.de > <mailto:jtuchel@objektfabrik.de> <jtuchel(a)objektfabrik.de > <mailto:jtuchel@objektfabrik.de>> wrote: > > Happy new year to all of you! May 2021 be an increasingly less crazy > year than 2020... > > > I have a question that sounds a bit strange, but we have two effects > with NeoCSVReader related to wrong definitions of the reader. > > One effect is that reading a Stream #upToEnd leads to an endless > loop, > the other is that the Reader produces twice as many objects as > there are > lines in the file that is being read. > > In both scenarios, the reason is that the CSV Reader has a wrong > number > of column definitions. > > Of course that is my fault: why do I feed a "malformed" CSV file > to poor > NeoCSVReader? > > Let me explain: we have a few import interfaces which end users can > define using a more or less nice assistant in our Application. The > CSV > files they upload to our App come from third parties like payment > providers, banks and other sources. These change their file > structures > whenever they feel like it and never tell anybody. So a CSV import > that > may have been working for years may one day tear a whole web server > image down because of a wrong number of fieldAccessors. This is > bad on > many levels. > > You can easily try the doubling effect at home: define a working CSV > Reader and comment out one of the addField: commands before you > use the > NeoCSVReader to parse a CSV file. Say your CSV file has 3 lines > with 4 > columns each. If you remove one of the fieldAccessors, an #upToEnd > will > yoield an Array of 6 objects rather than 3. > > I haven't found the reason for the cases where this leads to an > endless > loop, but at least this one is clear... > > I *guess* this is due to the way #readEndOfLine is implemented. It > seems > to not peek forward to the end of the line. I have the gut feeling > #peekChar should peek instead of reading the #next character form the > input Stream, but #peekChar has too many senders to just go ahead and > mess with it ;-) > > So I wonder if there are any tried approaches to this problem. > > One thing I might do is not use #upToEnd, but read each line using > PositionableStream>>#nextLine and first check each line if the > number of > separators matches the number of fieldAccessors minus 1 (and go > through > the hoops of handling separators in quoted fields and such...). > Only if > that test succeeds, I would then hand a Stream with the whole line to > the reader and do a #next. > > This will, however, mean a lot of extra cycles for large files. Of > course I could do this only for some lines, maybe just the first one. > Whatever. > > > But somehow I have the feeling I should get an exception telling > me the > line is not compatible to the Reader's definition or such. Or > #readAtEndOrEndOfLine should just walk the line to the end and ignore > the rest of the line, returnong an incomplete object.... > > > Maybe I am just missing the right setting or switch? What best > practices > did you guys come up with for such problems? > > > Thanks in advance, > > > Joachim > > > > > > > > > > > > > > > > > > -- ----------------------------------------------------------------------- Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de Fliederweg 1 http://www.objektfabrik.de D-71640 Ludwigsburg http://joachimtuchel.wordpress.com Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by StÃ©phane Ducasse

Another point: In open-source and in this community. Either the code people mentioned is open-source and accessible or it does not exist. If it does not exist then this is easy :) S. > On 6 Jan 2021, at 05:10, Richard O'Keefe <raoknz(a)gmail.com> wrote: > > NeoCSVReader is described as efficient. What is that > in comparison to? What benchmark data are used? > Here are benchmark results measured today. > (5,000 data line file, 9,145,009 characters). > method time(ms) > Just read characters 410 > CSVDecoder>>next 3415 astc's CSV reader (defaults). 1.26 x CSVParser > NeoCSVReader>>next 4798 NeoCSVReader (default state). 1.78 x CSVParser > CSVParser>>next 2701 pared-to-the-bone CSV reader. 1.00 reference. > > (10,000 data line file, 1,544,836 characters). > method time(ms) > Just read characters 93 > CSVDecoder>>next 530 astc's CSV reader (defaults). 1.26 x CSVParser > NeoCSVReader>>next 737 NeoCSVReader (default state). 1.75 x CSVParser > CSVParser>>next 421 pared-to-the-bone CSV reader. 1.00 reference. > > CSVParser is just 78 lines and is not customisable. It really is > stripped to pretty much an absolute minimum. All of the parsers > were configured (if that made sense) to return an Array of Strings. > Many of the CSV files I've worked with use short records instead > of ending a line with a lot of commas. Some of them also have the occasional stray comment off to the right, not mentioned in the header. > I've also found it necessary to skip multiple lines at the beginning > and/or end. (Really, some government agencies seem to have NO idea > that anyone might want to do more with a CSV file than eyeball it in > Excel.) > > If there is a benchmark suite I can use to improve CSVDecoder, > I would like to try it out. > > On Tue, 5 Jan 2021 at 02:36, jtuchel(a)objektfabrik.de <mailto:jtuchel@objektfabrik.de> <jtuchel(a)objektfabrik.de <mailto:jtuchel@objektfabrik.de>> wrote: > Happy new year to all of you! May 2021 be an increasingly less crazy > year than 2020... > > > I have a question that sounds a bit strange, but we have two effects > with NeoCSVReader related to wrong definitions of the reader. > > One effect is that reading a Stream #upToEnd leads to an endless loop, > the other is that the Reader produces twice as many objects as there are > lines in the file that is being read. > > In both scenarios, the reason is that the CSV Reader has a wrong number > of column definitions. > > Of course that is my fault: why do I feed a "malformed" CSV file to poor > NeoCSVReader? > > Let me explain: we have a few import interfaces which end users can > define using a more or less nice assistant in our Application. The CSV > files they upload to our App come from third parties like payment > providers, banks and other sources. These change their file structures > whenever they feel like it and never tell anybody. So a CSV import that > may have been working for years may one day tear a whole web server > image down because of a wrong number of fieldAccessors. This is bad on > many levels. > > You can easily try the doubling effect at home: define a working CSV > Reader and comment out one of the addField: commands before you use the > NeoCSVReader to parse a CSV file. Say your CSV file has 3 lines with 4 > columns each. If you remove one of the fieldAccessors, an #upToEnd will > yoield an Array of 6 objects rather than 3. > > I haven't found the reason for the cases where this leads to an endless > loop, but at least this one is clear... > > I *guess* this is due to the way #readEndOfLine is implemented. It seems > to not peek forward to the end of the line. I have the gut feeling > #peekChar should peek instead of reading the #next character form the > input Stream, but #peekChar has too many senders to just go ahead and > mess with it ;-) > > So I wonder if there are any tried approaches to this problem. > > One thing I might do is not use #upToEnd, but read each line using > PositionableStream>>#nextLine and first check each line if the number of > separators matches the number of fieldAccessors minus 1 (and go through > the hoops of handling separators in quoted fields and such...). Only if > that test succeeds, I would then hand a Stream with the whole line to > the reader and do a #next. > > This will, however, mean a lot of extra cycles for large files. Of > course I could do this only for some lines, maybe just the first one. > Whatever. > > > But somehow I have the feeling I should get an exception telling me the > line is not compatible to the Reader's definition or such. Or > #readAtEndOrEndOfLine should just walk the line to the end and ignore > the rest of the line, returnong an incomplete object.... > > > Maybe I am just missing the right setting or switch? What best practices > did you guys come up with for such problems? > > > Thanks in advance, > > > Joachim > > > > > > > > > > > > > > > > > > -------------------------------------------- StÃ©phane Ducasse http://stephane.ducasse.free.fr / http://www.pharo.org 03 59 35 87 52 Assistant: Aurore Dalle FAX 03 59 57 78 50 TEL 03 59 35 86 16 S. Ducasse - Inria 40, avenue Halley, Parc Scientifique de la Haute Borne, BÃ¢t.A, Park Plaza Villeneuve d'Ascq 59650 France

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by StÃ©phane Ducasse

John Iâm sorry to tell you that but you cannot write mail like that without telling us where is the code of CVSParser. You cannot basically discredit the work on Sven without providing code to compare. S. > On 6 Jan 2021, at 05:10, Richard O'Keefe <raoknz(a)gmail.com> wrote: > > NeoCSVReader is described as efficient. What is that > in comparison to? What benchmark data are used? > Here are benchmark results measured today. > (5,000 data line file, 9,145,009 characters). > method time(ms) > Just read characters 410 > CSVDecoder>>next 3415 astc's CSV reader (defaults). 1.26 x CSVParser > NeoCSVReader>>next 4798 NeoCSVReader (default state). 1.78 x CSVParser > CSVParser>>next 2701 pared-to-the-bone CSV reader. 1.00 reference. > > (10,000 data line file, 1,544,836 characters). > method time(ms) > Just read characters 93 > CSVDecoder>>next 530 astc's CSV reader (defaults). 1.26 x CSVParser > NeoCSVReader>>next 737 NeoCSVReader (default state). 1.75 x CSVParser > CSVParser>>next 421 pared-to-the-bone CSV reader. 1.00 reference. > > CSVParser is just 78 lines and is not customisable. It really is > stripped to pretty much an absolute minimum. All of the parsers > were configured (if that made sense) to return an Array of Strings. > Many of the CSV files I've worked with use short records instead > of ending a line with a lot of commas. Some of them also have the occasional stray comment off to the right, not mentioned in the header. > I've also found it necessary to skip multiple lines at the beginning > and/or end. (Really, some government agencies seem to have NO idea > that anyone might want to do more with a CSV file than eyeball it in > Excel.) > > If there is a benchmark suite I can use to improve CSVDecoder, > I would like to try it out. > > On Tue, 5 Jan 2021 at 02:36, jtuchel(a)objektfabrik.de <mailto:jtuchel@objektfabrik.de> <jtuchel(a)objektfabrik.de <mailto:jtuchel@objektfabrik.de>> wrote: > Happy new year to all of you! May 2021 be an increasingly less crazy > year than 2020... > > > I have a question that sounds a bit strange, but we have two effects > with NeoCSVReader related to wrong definitions of the reader. > > One effect is that reading a Stream #upToEnd leads to an endless loop, > the other is that the Reader produces twice as many objects as there are > lines in the file that is being read. > > In both scenarios, the reason is that the CSV Reader has a wrong number > of column definitions. > > Of course that is my fault: why do I feed a "malformed" CSV file to poor > NeoCSVReader? > > Let me explain: we have a few import interfaces which end users can > define using a more or less nice assistant in our Application. The CSV > files they upload to our App come from third parties like payment > providers, banks and other sources. These change their file structures > whenever they feel like it and never tell anybody. So a CSV import that > may have been working for years may one day tear a whole web server > image down because of a wrong number of fieldAccessors. This is bad on > many levels. > > You can easily try the doubling effect at home: define a working CSV > Reader and comment out one of the addField: commands before you use the > NeoCSVReader to parse a CSV file. Say your CSV file has 3 lines with 4 > columns each. If you remove one of the fieldAccessors, an #upToEnd will > yoield an Array of 6 objects rather than 3. > > I haven't found the reason for the cases where this leads to an endless > loop, but at least this one is clear... > > I *guess* this is due to the way #readEndOfLine is implemented. It seems > to not peek forward to the end of the line. I have the gut feeling > #peekChar should peek instead of reading the #next character form the > input Stream, but #peekChar has too many senders to just go ahead and > mess with it ;-) > > So I wonder if there are any tried approaches to this problem. > > One thing I might do is not use #upToEnd, but read each line using > PositionableStream>>#nextLine and first check each line if the number of > separators matches the number of fieldAccessors minus 1 (and go through > the hoops of handling separators in quoted fields and such...). Only if > that test succeeds, I would then hand a Stream with the whole line to > the reader and do a #next. > > This will, however, mean a lot of extra cycles for large files. Of > course I could do this only for some lines, maybe just the first one. > Whatever. > > > But somehow I have the feeling I should get an exception telling me the > line is not compatible to the Reader's definition or such. Or > #readAtEndOrEndOfLine should just walk the line to the end and ignore > the rest of the line, returnong an incomplete object.... > > > Maybe I am just missing the right setting or switch? What best practices > did you guys come up with for such problems? > > > Thanks in advance, > > > Joachim > > > > > > > > > > > > > > > > > > -------------------------------------------- StÃ©phane Ducasse http://stephane.ducasse.free.fr / http://www.pharo.org 03 59 35 87 52 Assistant: Aurore Dalle FAX 03 59 57 78 50 TEL 03 59 35 86 16 S. Ducasse - Inria 40, avenue Halley, Parc Scientifique de la Haute Borne, BÃ¢t.A, Park Plaza Villeneuve d'Ascq 59650 France

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by Richard O'Keefe

NeoCSVReader is described as efficient. What is that in comparison to? What benchmark data are used? Here are benchmark results measured today. (5,000 data line file, 9,145,009 characters). method time(ms) Just read characters 410 CSVDecoder>>next 3415 astc's CSV reader (defaults). 1.26 x CSVParser NeoCSVReader>>next 4798 NeoCSVReader (default state). 1.78 x CSVParser CSVParser>>next 2701 pared-to-the-bone CSV reader. 1.00 reference. (10,000 data line file, 1,544,836 characters). method time(ms) Just read characters 93 CSVDecoder>>next 530 astc's CSV reader (defaults). 1.26 x CSVParser NeoCSVReader>>next 737 NeoCSVReader (default state). 1.75 x CSVParser CSVParser>>next 421 pared-to-the-bone CSV reader. 1.00 reference. CSVParser is just 78 lines and is not customisable. It really is stripped to pretty much an absolute minimum. All of the parsers were configured (if that made sense) to return an Array of Strings. Many of the CSV files I've worked with use short records instead of ending a line with a lot of commas. Some of them also have the occasional stray comment off to the right, not mentioned in the header. I've also found it necessary to skip multiple lines at the beginning and/or end. (Really, some government agencies seem to have NO idea that anyone might want to do more with a CSV file than eyeball it in Excel.) If there is a benchmark suite I can use to improve CSVDecoder, I would like to try it out. On Tue, 5 Jan 2021 at 02:36, jtuchel(a)objektfabrik.de < jtuchel(a)objektfabrik.de> wrote: > Happy new year to all of you! May 2021 be an increasingly less crazy > year than 2020... > > > I have a question that sounds a bit strange, but we have two effects > with NeoCSVReader related to wrong definitions of the reader. > > One effect is that reading a Stream #upToEnd leads to an endless loop, > the other is that the Reader produces twice as many objects as there are > lines in the file that is being read. > > In both scenarios, the reason is that the CSV Reader has a wrong number > of column definitions. > > Of course that is my fault: why do I feed a "malformed" CSV file to poor > NeoCSVReader? > > Let me explain: we have a few import interfaces which end users can > define using a more or less nice assistant in our Application. The CSV > files they upload to our App come from third parties like payment > providers, banks and other sources. These change their file structures > whenever they feel like it and never tell anybody. So a CSV import that > may have been working for years may one day tear a whole web server > image down because of a wrong number of fieldAccessors. This is bad on > many levels. > > You can easily try the doubling effect at home: define a working CSV > Reader and comment out one of the addField: commands before you use the > NeoCSVReader to parse a CSV file. Say your CSV file has 3 lines with 4 > columns each. If you remove one of the fieldAccessors, an #upToEnd will > yoield an Array of 6 objects rather than 3. > > I haven't found the reason for the cases where this leads to an endless > loop, but at least this one is clear... > > I *guess* this is due to the way #readEndOfLine is implemented. It seems > to not peek forward to the end of the line. I have the gut feeling > #peekChar should peek instead of reading the #next character form the > input Stream, but #peekChar has too many senders to just go ahead and > mess with it ;-) > > So I wonder if there are any tried approaches to this problem. > > One thing I might do is not use #upToEnd, but read each line using > PositionableStream>>#nextLine and first check each line if the number of > separators matches the number of fieldAccessors minus 1 (and go through > the hoops of handling separators in quoted fields and such...). Only if > that test succeeds, I would then hand a Stream with the whole line to > the reader and do a #next. > > This will, however, mean a lot of extra cycles for large files. Of > course I could do this only for some lines, maybe just the first one. > Whatever. > > > But somehow I have the feeling I should get an exception telling me the > line is not compatible to the Reader's definition or such. Or > #readAtEndOrEndOfLine should just walk the line to the end and ignore > the rest of the line, returnong an incomplete object.... > > > Maybe I am just missing the right setting or switch? What best practices > did you guys come up with for such problems? > > > Thanks in advance, > > > Joachim > > > > > > > > > > > > > > > > > > >

Jan. 6, 2021

Re: NeoCSVReader and wrong number of fieldAccessors

by jtuchel＠objektfabrik.de

Sven, I tested your change with the file and filter (our own way of defining csv mappings by the end users) which used to send our application into an endless loop. And voila: we get an exception instead of a frozen image! I will give the conversion errors a test drive tomorrow. I am absolutely happy with your change. Thank you very much. Joachim P.S: I even learned a little bit about Iceberg. I am not really sure each of my mouse clicks made sense, but I had your commit in the image and could test it and port the deltas over to my Smalltalk dialect... Am 05.01.21 um 19:52 schrieb jtuchel(a)objektfabrik.de: > Hi Sven, > > > all I can say is: wow. I have no words. > > I will have to learn a bit about Pharo and github real quick now in > order to try your changes.... > > Thank you very much. I'll give you feedback as fast as I can. > > (And forget my questions about #readAtEndOrEndOfLine. I somhow didn't > understand it is expected to return a Boolean. Not sure why. I thought > of 'read' as a command, not a question in simple past..., so I thought > its job should be to read the rest of the line if we're not there yet) > > > Joachim > > > > > > > > > > Am 05.01.21 um 17:49 schrieb Sven Van Caekenberghe: >> Hi Joachim, >> >> Have a look at the following commit: >> >> https://github.com/svenvc/NeoCSV/commit/a3d6258c28138fe3b15aa03ae71cf1e0770… >> >> and specifically the added unit tests. These should help clarify the >> new behaviour. >> >> If anything is not clear, please ask. >> >> HTH, >> >> Sven >> >>> On 5 Jan 2021, at 08:49, jtuchel(a)objektfabrik.de wrote: >>> >>> Sven, >>> >>> first of all thanks a lot for taking your time with this! >>> >>> Your test case is so beautifully small I can't believe it ;-) >>> >>> While I think some kind of validation could help with parsing CSV, I >>> remember reading your comment on this in some other discussion long >>> ago. You wrote you don't see it as a responsibility of a parser and >>> that you wouldn't want to add this to NeoCSV. I must say I tend to >>> agree mostly. Whatever you do at parsing can only cover part of the >>> problems related to validation. There will be checks that require >>> access to other fields from the same line, or some object that will >>> be the owner of the Collection that you are just importing, so a lot >>> of validation must be done after parsing anyways. >>> >>> So I think we can mostly ignore the validation part. Whatever a >>> reader will do, it will not be good enough. >>> >>> A nice way of exposing conversion errors for fields created with >>> #addField:converter: would help a lot, however. >>> >>> I am glad you agree on the underflow bug. This is more a question of >>> well-formedness than of validation. If a reader finds out it doesn't >>> fit for a file structure, it should tell the user/developer about it >>> or at least gracefully return some more or less incomplete object >>> resembling what it could parse. But it shouldn't cross line borders >>> and return a wrong number of objects. >>> >>> >>> I will definitely continue my hunt for the endless loop. It is not >>> an ideal situation if one user of our Seaside Application completely >>> blocks an image that may be serving a few other users by just using >>> a CVS parser that doesn't fit with the file. I suspect this has to >>> do with #readEndOfLine in some special case of the underflow bug, >>> but cannot prove it yet. But I have a file and parser that reliably >>> goes into an endless loop. I just need to isolate the bare CSV >>> parsing from the whole machinery we've build around NeoCSV reader >>> for these user-defined mappings... I wouldn't be surprised if it is >>> a problem buried somewhere in our preparations in building a parser >>> from user-defined data... I will report my progress here, I promise! >>> >>> >>> One question I keep thinking about in NeoCSV: You implemented a >>> method called #peekChar, but it doesn't #peek. It buffers a >>> character and does read the #next character. I tried replacing the >>> #next with #peek, but that is definitely a shortcut to 100% CPU, >>> because #peekChar is used a lot, not only for consuming an "unmapped >>> remainder" of a line... I somehow have the feeling that at least in >>> #readEndOfLine the next char should bee peeked instead of consumed >>> in order to find out if it's workload or part of the crlf/lf... >>> Shouldn't a reader step forward by using #peek to see whether there >>> is more data after all fieldAccessors have been applied to the line >>> (see #readNextRecordAsObject)? Otoh, at one point the reader has to >>> skip to the next line, so I am not sure if peek has any place >>> here... I need to debug a little more to understand... >>> >>> >>> >>> Joachim >>> >>> >>> >>> >>> >>> >>> Am 04.01.21 um 20:57 schrieb Sven Van Caekenberghe: >>>> Hi Joachim, >>>> >>>> Thanks for the detailed feedback. This is most helpful. I need to >>>> think more about this and experiment a bit. This is what I came up >>>> with in a Workspace/Playground: >>>> >>>> input := 'foo,1 >>>> bar,2 >>>> foobar,3'. >>>> >>>> (NeoCSVReader on: input readStream) upToEnd. >>>> (NeoCSVReader on: input readStream) addField; upToEnd. >>>> (NeoCSVReader on: input readStream) addField; addField; addField; >>>> upToEnd. >>>> >>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; >>>> addField: [ :obj :str | obj at: #one put: str]; upToEnd. >>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; >>>> addField: [ :obj :str | obj at: #one put: str]; addField: [ :obj >>>> :str | obj at: #two put: str]; addField: [ :obj :str | obj at: >>>> #three put: str]; upToEnd. >>>> (NeoCSVReader on: input readStream) recordClass: Dictionary; >>>> emptyFieldValue: #passNil; addField: [ :obj :str | obj at: #one >>>> put: str]; addField: [ :obj :str | obj at: #two put: str]; >>>> addField: [ :obj :str | obj at: #three put: str]; upToEnd. >>>> >>>> In my opinion there are two distinct issues: >>>> >>>> 1. what to do when you define a specific number of fields to be >>>> read and there are not enough of them in the input (underflow), or >>>> there are too many of them in the input (overflow). >>>> >>>> it is clear that the underflow case is wrong and a bug that has to >>>> be fixed. >>>> the overflow case seems OK (resulting in nil fields) >>>> >>>> 2. to validate the input (a functionality not yet present) >>>> >>>> this would basically mean to signal an error in the under or >>>> overflow case. >>>> but wrong type conversions should be errors too. >>>> >>>> I understand that you want to validate foreign input. >>>> >>>> It is a pity that you cannot produce an infinite loop example, that >>>> would also be useful. >>>> >>>> That's it for now, I will come back to you. >>>> >>>> Regards, >>>> >>>> Sven >>>> >>>>> On 4 Jan 2021, at 14:46, jtuchel(a)objektfabrik.de wrote: >>>>> >>>>> Please find attached a small test case to demonstrate what I mean. >>>>> There is just some nonsense Business Object class and a simple >>>>> test case in this fileout. >>>>> >>>>> >>>>> Am 04.01.21 um 14:36 schrieb jtuchel(a)objektfabrik.de: >>>>>> Happy new year to all of you! May 2021 be an increasingly less >>>>>> crazy year than 2020... >>>>>> >>>>>> >>>>>> I have a question that sounds a bit strange, but we have two >>>>>> effects with NeoCSVReader related to wrong definitions of the >>>>>> reader. >>>>>> >>>>>> One effect is that reading a Stream #upToEnd leads to an endless >>>>>> loop, the other is that the Reader produces twice as many objects >>>>>> as there are lines in the file that is being read. >>>>>> >>>>>> In both scenarios, the reason is that the CSV Reader has a wrong >>>>>> number of column definitions. >>>>>> >>>>>> Of course that is my fault: why do I feed a "malformed" CSV file >>>>>> to poor NeoCSVReader? >>>>>> >>>>>> Let me explain: we have a few import interfaces which end users >>>>>> can define using a more or less nice assistant in our >>>>>> Application. The CSV files they upload to our App come from third >>>>>> parties like payment providers, banks and other sources. These >>>>>> change their file structures whenever they feel like it and never >>>>>> tell anybody. So a CSV import that may have been working for >>>>>> years may one day tear a whole web server image down because of a >>>>>> wrong number of fieldAccessors. This is bad on many levels. >>>>>> >>>>>> You can easily try the doubling effect at home: define a working >>>>>> CSV Reader and comment out one of the addField: commands before >>>>>> you use the NeoCSVReader to parse a CSV file. Say your CSV file >>>>>> has 3 lines with 4 columns each. If you remove one of the >>>>>> fieldAccessors, an #upToEnd will yoield an Array of 6 objects >>>>>> rather than 3. >>>>>> >>>>>> I haven't found the reason for the cases where this leads to an >>>>>> endless loop, but at least this one is clear... >>>>>> >>>>>> I *guess* this is due to the way #readEndOfLine is implemented. >>>>>> It seems to not peek forward to the end of the line. I have the >>>>>> gut feeling #peekChar should peek instead of reading the #next >>>>>> character form the input Stream, but #peekChar has too many >>>>>> senders to just go ahead and mess with it ;-) >>>>>> >>>>>> So I wonder if there are any tried approaches to this problem. >>>>>> >>>>>> One thing I might do is not use #upToEnd, but read each line >>>>>> using PositionableStream>>#nextLine and first check each line if >>>>>> the number of separators matches the number of fieldAccessors >>>>>> minus 1 (and go through the hoops of handling separators in >>>>>> quoted fields and such...). Only if that test succeeds, I would >>>>>> then hand a Stream with the whole line to the reader and do a #next. >>>>>> >>>>>> This will, however, mean a lot of extra cycles for large files. >>>>>> Of course I could do this only for some lines, maybe just the >>>>>> first one. Whatever. >>>>>> >>>>>> >>>>>> But somehow I have the feeling I should get an exception telling >>>>>> me the line is not compatible to the Reader's definition or such. >>>>>> Or #readAtEndOrEndOfLine should just walk the line to the end and >>>>>> ignore the rest of the line, returnong an incomplete object.... >>>>>> >>>>>> >>>>>> Maybe I am just missing the right setting or switch? What best >>>>>> practices did you guys come up with for such problems? >>>>>> >>>>>> >>>>>> Thanks in advance, >>>>>> >>>>>> >>>>>> Joachim >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>> -- >>>>> ----------------------------------------------------------------------- >>>>> >>>>> Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de >>>>> Fliederweg 1 http://www.objektfabrik.de >>>>> D-71640 Ludwigsburg http://joachimtuchel.wordpress.com >>>>> Telefon: +49 7141 56 10 86 0Â Â Â Â Â Â Â Â Fax: +49 7141 56 10 86 1 >>>>> >>>>> >>>>> <NeoCSVEndlessLoopTest.st> >>> >>> -- >>> ----------------------------------------------------------------------- >>> Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de >>> Fliederweg 1 http://www.objektfabrik.de >>> D-71640 Ludwigsburg http://joachimtuchel.wordpress.com >>> Telefon: +49 7141 56 10 86 0Â Â Â Â Â Â Â Â Fax: +49 7141 56 10 86 1 >>> > -- ----------------------------------------------------------------------- Objektfabrik Joachim Tuchel mailto:jtuchel@objektfabrik.de Fliederweg 1 http://www.objektfabrik.de D-71640 Ludwigsburg http://joachimtuchel.wordpress.com Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1

Jan. 5, 2021