Hi, Adrian, On Sat, Dec 7, 2024 at 5:07 PM Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote: > > On 12/7/24 12:17, Igor Korot wrote: > > Hi, Adrian, > > > > On Sat, Dec 7, 2024 at 12:32 PM Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote: > >> > >> On 12/7/24 09:59, Igor Korot wrote: > >>> Hi, Adrian, > >>> > >>> On Sat, Dec 7, 2024 at 11:18 AM Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote: > >>>> > >>>> On 12/6/24 19:36, Igor Korot wrote: > >>>>> Hi, All, > >>>>> > >>>>> When my application starts up, ot creates some tables and insert records > >>>>> in them. > >>>>> > >>>>> When the app starts for the second time it should check if the tables > >>>>> and the records in them are exist and skip the process. > >>>> > >>>> Does this also apply to starts after the second time? > >>> > >>> Yes, it does. > >>> > >>> However, if the new table is created in the meantime - the new record > >>> should be created, because it is not there yet. > >> > >> What determines that a new table needs to be created and populated? > > > > Consider the following scenario: > > I did and it made me start twitching. Good.. > > > > > 1. Program is installed. > > 2. Program is started for the first time. > > 3. My tables are created and populated > > What distinguishes your tables from other users' tables? I am making the tables and naming them with a specific pattern. Now I'm curious - if I start psql and will want to create a table named pg_am, what will happen? I presume psql will produce error saying that the system table with that name exists and the user can't create ome. Am I right? > > > 4. Program is executed. > > 5. User closes the program. > > 6.. Later on the user decides that there is a need > > for another table (inside psql or any other client) > > The above is where I started twitching. > > How do you keep them out of your tables? My tables are named with the specific pattern. Also - see above. > > How do you get these changes to play nice with the existing structure? Again - not sure what you mean here.... > > > 7. Then the program starts for the second time. > > > > At this time all my tables that were created will stay (courtesy > > of CREATE TABLE IF NOT EXIST). > > You are depending on folks not knowing about DROP TABLE and/or you > having thought out the permissions for access thoroughly. If one of my tables will be dropped - it will be re-created. I'm using CREATE TABLE IF NOT EXIST. > > > > All records that were there are staying unchanged. > > INSERT/UPDATE against your tables is not a possibility? It is.. All I;m saying that when the app starts-up, this is done automatically And if the user decides to insert some data - that's on him > > > However, for the table that was made in between the runs > > will be added > > > > Now if the program is installed on 2 different machines > > and started simultaneously on both - I want to ensure that > > only 1 set of tables is made and only 1 set of records in them > > is available > > I assume this means they are both pointing at the same instance of a > database? Correct. > > This is the part that confuses me. > > If you are going to allow ad hoc and at will changes how do you know > what is actually the correct change? I don't. Think about MS ACCESS-like applications. ACCESS creates the internal tables to keep track of some internals. Is there a possibility of a clash with the user table? Ofc there is. But MS is still doing it nevertheless, because chances of this occurring are really slim. And if a user acquire access to those internal tables and start modify them and in the process screw something up, well he uses MS product as a developer and so should know better as a developer And if MS can do it - why can't I? > > > > > Now, the creation/population is done inside a transaction. > > I'm not sure that a transaction is going to solve the issue I raised > above, it will just make one thing happen with no guarantee that it is > the correct outcome. What is considered correct outcome is strongly on user if we are talking about my app. > > > >> Are you talking about the front end that the user launches or the > >> backend that runs the database or something else? > > > > Front-end. > > This is a C++ app. > > To me this is the tail wagging the dog. The thought of allowing users to > change the database structure and you dealing with it after the fact is > just disturbing to me. But not to me. My application targets developers, not end users. Thank you. > > > > >> > >> > >>> > >>> Thank you. > > -- > Adrian Klaver > adrian.klaver@xxxxxxxxxxx >
