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Writing a foreign data wrapper

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Writing a foreign data wrapper
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Experiences with Informix Writing a foreign data wrapper (FDW) for PostgreSQL seems easy. However, there are many pitfalls. This talk will cover experiences from writing a FDW for Informix and will discuss problems with client libraries, data type mapping, optimizer support and performance related topics. Interested attendees will get a short overview on what they can expect from a FDW and (hopefully) learn something to do it better.
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but good morning my name is bound hand and working for a German company said at the as a database consulting consult trauma-focused focus PostgreSQL and I'm trying to go about writing for data about basically introducing the guy at that infrastructure on and what you need to consider when you to do actually to get a foreign data record for your so why not going to do is to introduce a certain on data and so on it's basically just code what will come to be implemented get on data that working so it's of why
foreign data a lot of missing in the SQL SQL and p any special mention of externally and this I have put a bunch of use cases where the values might be interesting these developments is I used them in the past it's migration proposes to use infrastructure for example if you have many many different or and don't from databases or source like wages in a fraction of what use post recording bulletins of works on the integrated data sources and process the data this all to integrate relational data sources in a relational database that's the interesting part 2 for example that you can view that services from so what chests of its own and these the nice talked with
but basically of working with a foreign data record is very easy but I'm going to start from the top ball and talk about somebody actually I use either going to use of for the rest of the statement the dozens I you need a set of conditions creates a using the foreign data rather you are actually want to use this example from exploring the actually written on the connection options the use of that to map the PostgreSQL users foreign data sources is can be another databases for outside or just looking for the unwanted source that the following table itself using this so that the initial so that means you actually to connect to and the front options are pushed on cross-sectoral and actually performing according to these permits the remote theory for example in connections but is actually someone using and I want to do which ruled that society has a part of you but on the other hand you want to know this the mother and his her FIL you have to follow the steps you actually can be very different 10 trust hostage use it like normal was that visiting reviews on it you can fill it out and trying to those tables that's no problem at all you can't indexes on then you can write on the tables of foreign interests are really only if the possible unfortunately but there's something planned but and to get the right from that arose of the what
we need to accomplish and interface to the parameters of course but nonetheless our posters the W. API and hopefully bring to in the next couple ideology view are also it's basically all synchronizing remote data sources and error conditions so and you have remote database of services like new to synchronize because can't trust role of the transactional away in PostgreSQL with all the allocating memory structure form of reports on so as to summarize the our hands and missing I have that the possible not think about Arab just before so that's 1 of the most popular all of this kind think about it for a then remote data mapping how to map the remote types suppose that they that's all that and times that because you have to think about many many areas and problems on my face with them but mostly on trust regarding integration of remote for thank there's although would come project for patent through this might be of interest because of its wouldn't Python and you can then right your own for Python this easier than writing 1 can see I had a following that it's not so that hopefully you the only see it for example but might be although this is a great we compose a so that our actually count on it and I have also plans to submit my involving SMEs for each conference but also ran out time the managed communities of heat islands I put them 1 I think decode this straightforward OK let's stop so the very 1st thing you need to implement are actually 2 functions I analytic data function for example the following so far underdeveloped and informants 400 religion this what are defined in the extension of going to write for that you have in to write an extension and not covering extension and your so on redirected the condition of all trees and multiplied but that's basically what you write in its cluster would extension and the reflective of at least defined Hammond related forms the hand loss functions
responsible to which is the the FTW callbacks was because the of this basically enough what you need to do and inference data Handbook just make the WTO structure with make knowledge when I signed a callback books structure they would later call that is a little more complicated complicated needs to have some intelligence and this poses to 188 . 8 options of passed on prefrontal and all 4 and Table you go back in the slides the
rest of you if you want to use those funds of just passed on you for but there will form the unknown are up and the use and such thing I to get this function untransformed both options given foreign data options that's just a little death and structures you can then look through give and I trusted the strings job stock current strings pushed you can simply use frequent to check whether it's known optional on and use options the options which you want to call up to and passed on any options you would like all rechecked options for example no problem but the main proposal to what call but I've seen in I think it's all of the following it also possible negation against data or data type and of course this could have I'm doing that in the planning stage not here but might be option to 1 the sanity check is assigned because they that the last 1 all right 1st 1 for example it's love the principle of surprise
but that that's the main cause of of that will be called the at the disposal
and had 503 before in front of H. 5 post consoles and I recommend that because it defines some how functions both of funds are not are documented in the 9 documentation down using in a nine-month communication as you mentioned here but there are some of the functions for example information about the following slowly up the using inference tracked formants or objectives emitting returning structured information of use of mapping actually retrieve the user like when he and so when foreign data on function graph on tables the most interesting function here because can get from table definitions that not because of the form that's not containing the following table structure information about Table itself for example which still is it using which use the mapping and so on which options are passed on you can get them from the goods
of our data have all of that is implemented in their callback routines 5 0 that's shown here and plan for instead and explained from begin France then iterate Canada and for instance called that our on on different stages like some of the planned for and skin is wrong and you find it's it's proposes to retrieve you're foreign scan costs and role as the main to initialize supporting structural form obsessed that's basically what I'm doing planning stage because we therefore on internal database it's long up used to use to a remote database cost estimates so you need to establish a data connection anyways retrieved and so I'm basically is that be this connection at the planning stage the planning in full and so the cost estimates of basically contained in the plan for and was not in full power those structures some important
fields which has shown with the set code here the most important of these are in the planning notes so if you are entering a planned for instance Kullback the 1st thing you do is allocating FTW and structural McDonald's integrated initializes stock here for example I'm hungry a test database connections of a new database connection to expensive and cash database connections so waiting higher that I'm getting the estimated rose from the phonics connections initializing the basis for rows and with values with the average size in bytes and then calculating balls this is a very crude many need some more sophisticated here morphine right but but and that's actually what I have come up with at the moment the just calculates the rows did you grow estimate costs based on the average with and the number of rows and assumes can for example right at me about process of the connection so . you but you actually have the plan from instead I think it's got 9 2 words divided into 3 actually called x amount gets little size get on a get 4 and size before and after they get from plan so I'm not covering this year from to that moment gets lots of and that's what you need to do for 9 1 9 2 has significant change you we the but that's just example from you just about hiring of new connection or catch connections this the this just before all yeah it's just thing about the new connection is more expensive than best connection but you can also hammering of this so well yeah it would be more interesting to get a magnitude and pushed on for example with foreign data report something like that because of the use all so it would be I just but it's basically only asphalt a catch connection has basically already we use a table so it's busy for example in the cash flows from 1 remote database size such things but sampled that it's yeah cheaper to retrieve that the is the just the motion of it's not based on harmony for example I think the oracle of foreign available to is calculating because of course ring you're networks he assumes that can I Friday it may about per 2nd over a network connection calculates the cost based on the real estimated so with the 100 world you don't want to use no God the end result is so the and other proposes that for it when implemented that for example in my in my proof of concept for informants I just realized that makes because I don't I have to be free wrote the estimates from performance and image and the database connection there is always a little bit the of because then the connection is already catch because user database connection and begin form of for instance 1 and all of its reforms school the space Mason maybe a better option to test data which connects and was because that of not to re-establish database collection over so again that's going to be very expensive but if you want to say save for example like this example of when they but in the plant for instance data you need to use the FBW product on the so this is not because that will with Corky object I had use it so from but I don't the oracle foreign data about users it heavily it's 1st on the the test land of having to begin for instance states and it uses only have experimented with that they on that of the best moment to summarize the planet hasn't by a male constant dependent upon values list can testify to that private of stress you the plan right you know no it's a Winnebago just was just to come to push it obviously excuse that because of the tone of so but I think the the planet not pushing Donbass it's just coping that that's the reason why the speed of good balances the fields in the conference and instead base on based in Poland base rural populace based importance of list predicates actually that was also referenced in the reference from front table and recognition it's contained and that most much of the logic of the and so you don't need about oral anything about that you can use that for example transform that's with this expression to pushed on and remote they so for example you have where foreign table but i equals to 1 can FIL pushed on debt from the expression to read it all it's up to you how users and what each may all of their were toddlers saying basically all about specific common columns and very I have that the moment and the Chesterfield all and use content from and that so and code here is just show how to use it I'm basically interested and operands operated expressions but the base the base of input contains a list of suppress infrastructures those interested in for haven't cross value and if that expression equals to all expression bend might be of interest for me some ideas that I which should talk about actually I think you can even pushed on functional expressions of it and you know that there are more data sources of supporting substring replace so but that would be that hard
I so this 1 is just In this
example x and y expected but of course you have something more complicated connects so we have for instance use call x staff who was sort of coal that it has novel environments that present functions nature Prunskiene state and performance and to say still functions state values but it basically passed from data that for a scanning reminded muscles on the most interesting interesting thing here is that we start up our meters you all need for executing a remote or can you say it and after that the State of New for example if you will need to between i . com British army doesn't say when you are going to iterate FIL resulted from a remote database and find that this what I wanted something you will use it kind of texture on structure information catch structure of which genes is up to you would use most important thing that you have to distinguish explain explore analyze here just check with some it and I can't accept that it's the only way they are going to only explain all explain analyzed because was the same I expecting explain not to execute anything so no user-visible changes just which from the plan explain standard and once again
and I was told it expand from scan this random and explains you it started to inject information into a explain awkward on well if you don't have this information trust firm or you can return actually points sampled clearly which is used against the remote data source or for example the cost calculations you did additional across populations and timings it electrons can actually is executed the amount of other is a source routing although this the and fetches the data from the remote what you need to do is of obviously need to count data conversion here fetch the data material lots of his orbital to literature lists considered possible and when you're done you trust which amounted and to excuse stop the members of the state iterating through from results source and this is just a sample code again so but you need to do lose who return Justin 0 number all seem to I ought to initialize it will start in 1 of its requirements can the 2 slot and retrieve again from functions they up on the stand state of nodes and initializes according to the number of columns actually fiction the and it's red reconnaissance eigenvalues every value and poster session in the center of the ball you handle them all returnees have been so you just you contrast for example future just beginning to get a bit of that from that that's just when apply samples pointed to so they obeyed Manchester trying data from that of what could be text value or something like that you will have an intention you can use macros like insulin of 30 to get data from and something like that so at various the math was wrong it's kind value with it I think that adjusted you can't not some just couple from from the data the possible if they're going to and that and that it that is it what I think I'm also not sure really sure what Marx some of its theories can for instance actually you are required to implement what did we scanned points that actually does is to prepare the from the travel to handle these cancel basically if the iteration for instance starts from the beginning and ensure that that's really use cross handling because of or on us OK this the virtual world so example if you have a remote areas of stochastic what what's new because the division for example and says that you may need to be prepared for change parametres pushed on to the panel ultimately because depending on all can so it's not really required to return the same to and understands where that's the 1 you so it might be that set up to to do the of filter condition pushed onto the remote data sources iterated for instance and before of the year 1 OK but but you need to implement it yeah of i didn't accidentally by just listening the inform goes about and that's what wrong you need to that really to we all the because again with the so we can solve for from the all of the this is a so the war what I did was I accepted to food conditions in the beginning I don't we ever later and and when we scanning the problem yeah well I think the but that's really complicated told I'm not sure about that but it would really so all the things that you know about you you division of of the only so it's version of search 1 of the things you will the natural going war to so to and from scanned and he is the Kullback 1 and that's the next and so far foreign scan it finalizes everything you need to close the result set of remote data sources clean up your resources but the connection free memory and so on everything you don't need any more 1 of the things that we nice the but basically the flow moment scan with plant standing in front iterate and now you have to be pushed on the possible if you want some for reiterating for the conditions and you have with steps the reforms and put each fetch and based in the and for these you're going to use the next slide you don't have it with pasta but explained for instance here and if you have explain analyzed you have additional explain again with it with forms and stuff that's the main difference with 9 to the from instance as of I have already said is done actually 3 call that groups now what 9 2 this
not additionally is a callback routines for analyzed you can implement your own analyze function to collect remote statistics there I have you looked at it yes because time time yet for experimenting with it but the analyzed back continues quite some to retrieved the rental costs sort in and this is kind and let the planet to I I and who I think it is defined as the W wonderful is actually having an allowance function in some basic things the next the what might be an example of how to use so if you want to look at that look at the time the government right I'm going to but additional wrote about memory manager for all those who didn't actually that they can take in the past you have to take care of memory and spatial posters and allocates memory always have a number of contexts it is using external libraries almost and use their own to use their own medical memory allocation of functionality so take care about that you can't up to post was going to right thing on transactional need to clean up the and that's really important because in the memory Of course this debate and that's the scientists they want something pool or something like that this that the guy next thing I'm coming to a strong Lawrence that's so are handling you really need to synchronize data sources and you have an error conditions in post was bag at all and the remedy muscles it's all about you know come you can make sure that you know arrow and things not because you know they're passenger just presents the inspection and if you don't have any possibility reach again for example a function on a set of conditional random fields for something that you need to take care of the I'll thing to consider is to mapping of remote are or conditions to states there's codes and links in this post as the documentation highly commends really against that 0 what a chest met and 2 0 those groups are like of longing for example the informants are connection warning you contrasted to oppose those belonging and this until all what was 1 problem I had was that it was in data type conversion that I need to react to errors in the back and of to this is my remote data source the chance to not if you're using the correlated of quite some and functions and you are the issuing of Miss from data to the entire input function it's a result have to take care of but from Utrecht remember applications and then outside then you might use a pitch try to catch brought some very interesting infrastructure so on the the back and I think that's an example but to use I I had a problem of the form because you can as anybody using forest in the past but something happened as Alaska the instructions to the OK that In this case this is what basically I recall 2nd of this thing creator resources of the type input function uncomfortable again destroyed in our case have on data here and and to react with that and we throw connection bones suppressed or the following it's an idea from think 1 of the data type conversions if you had a memo data source it's good that you to think about how to use that data I will use post if you have a buffer streams but something they let you in this form its use is they because just called type function with them in type and prevents you get oppose that and that this occurs this the rights data type you want to use that is finally convertible types for example in the whole wide integer can be used directly for course I find that's always been by the course conditional with in there maybe it's a structured mandated and you can make it to a certain data but it's up to you have to decide if the thing about but once you get an answer so make sure the calling from the remote server side the of course because those are correct maybe you have to do the encoding conversion on but you have to take care for if you have remedy to this off with all doesn't find including correctly the in your model travel example yeah that's the next slides for example just to on you can use of course the post-clustering for structured get database conference actually that and coding digital encoding conversion of some of encoding conversions in band of the head of flies in the end the directory might be of interest to interesting here on to deal with that for example you have mentioned who want to access remote configuration files that you gave it encoded have validity this information from calls in the back of what direction here's an example together of practical functions so if you have the topic type led all Therefore interval yeah called the input widely variable it's easy just to and catch catching up which we the type 2 then extracted type include already from that function and
past and all the code before you can that function possible for to away from the call was always going to go to the various like to call functions available with 1 2 3 4 fulcrum and getting data for example that CTCs relocated box and you get actually about form PostgreSQL status as a base that that's basically everything so
I've basically done you have any questions the beginning of the the use of the word we don't like it yes what like the the right of the art rights away the right is what you have yes the words as the 1st thing we come to my mind is that you to have to synchronize the transaction of course remote data sources I think that that's the most interesting interesting part because if you have a transaction transaction cost was such must be able to to react to elect the transition to synchronize the basically two-phase commit 1 of the just like the 1 as sort of discussion had Heckerman because wh if you don't know what it was all about the rest of you the people 1 of the we 1 of the things that need to some of you know that the 1st of all all of the parents of these regions within the birth of the world on then the the that is something that is on the right road the long ones is you know that there is that is the in so if you want to know how and so that the buyers if that what during the 2nd World War have know what the concentration of awareness that this recommendation I'm taken from the source columns where the widow of such a book this going considerably faster and physical to what was it to this much you ask something which a truism just to store you know this 1 you this was the original you the cost of call war the rest of the world and the 1st of all we to be an because of the the rest of the world don't for there were 2 not only do you have you for here is 1 1 in the year so that it is that you have to show that was used and you thank you 1 of the things that you will use of you know the United 1 so what you want something that you want to use know utilization of the 1st 1 is the level of the past year have you find the 2 what about all the time and Kosovo on and I will not go into was of of of the rules of the form of a process that would be very you have to know the real world outside of the stuff that wall this but the rest of this is due to the yeah I don't know to where all of right to you you the versions rating when you are in the of that all of on the other of it this is a good at the time of the rest of the actually the only of in of the variance was you don't have to do this work the especially work in the end of the of the all the the yeah think of the relation with because always that now you which 1 the is the same for all what what do you think and a lot of sense bitching queries what this is a long way from well what can be for by solving when using falling so basically we created you are actually executing you need to queries to get so the actually for the kinetic so because of in detail kinescope 1st structure but that's basically yes I things on the client side but then actually executing the view of remote database query that's no more I think the most important thing I against people Oracle and from informants view is to contest a connection that need to be deleted because it involves connections that which is really expensive as now what I and my opinion from this is much slower all I think it's magnitude you would understand here you see that there was a lot of what we can actually introduce the but I implemented my own
connection catch with its basically and each step in the hash table which as living in the back end of top memory context and so managing and maintaining the Informix database connections which are going to be reused for the various 1 tables so what that states would have really really amount of time so and you have to be yeah Mr. should there be more machinery for yeah I think so but the problem is that each remote data source connection of different parameters so it's different for but somebody here using excuse uniform makes you are going to it's embedded SQL of what you're going to use like basically cheap the favorite and places inform music can CI about that's really complicated and we want to use it and it's just not identify all if you want to use use connection set connection identify objects just need to maintain the the correct distance that and what but I know that for example was the i bigger connection handles need more information so and imperfections should time that you might attach the old structures to catch up with and hash table it's not that complicated so the title was something like this and for example that's what I with the nature of the moment it's just that connection identify with structure attached to containing all necessary information we think that going to say and has is not complete that is for me so always before but but also tried to catch remote information from the following so for the various tables but abandoned that approach because of what not really require like foreign the time that but on the user anymore this so was but you have to create your own the building and this is the that was this point here is the of 1st this is that something on establish connection the this I'm not sure about that no this is an attribute of sequential steps we need to optimize I of my life there's no analogy has had a of the the beginning of the end of the was used you the issue of the United States the view the about the only only this is the same for the we the and you have to what you at the same time you there was another to have would be the 1st part was was then discussion about the index of some from 2 all the people in the so world the and and quality of life in the representative of the of the cost of the area you can be so what is the point the so I think so you have to generate the correct path and you get for path called you the words all of for you of the there was no discussion about indexes from from table recall so something like there's still a lot of and following closely to remember the then but what I think about trust in information that is an index which will allow for an index that what 1 you have a lot of and the people of the of the yeah modeling and any questions the we also present a family the the results of the things the get a resource for what happens the other way around this this the this is the work for the source or how of here the current is 0 what I started with just 1 and that was the plates alternatively to studying the source code or looking at this interpretations basic 9 2 has a somewhat improved documentation I think the top functions are actually imitation lots and I think you have to study of 2 to the cold and I pretty much command for example Lorentz had written the Oracle at the W 4 and it about he's but the destroyed data rivers the complete it has a prairie predicate pushed on the table the road list and you can various of approaches to pushed on function calls to an oracle database that it has it has no connection going to catch having it's pretty much complete it's a good starting point and I'm going to use the 4 and that of following successful but I haven't got and we use their code these moment I've already plentiful teaching combined around of on the water so give an island wiki page good progress
duality pitch are going to shift this is the which queries of with that you if you have questions about that the W. problems that the so that's that's the best form of we to talk