Re: Multiple inserts with two levels of foreign keys

[Ron <ronljohnsonjr@xxxxxxxxx>]

    Have you considered writing a stored procedure to process records
    that have been written to temporary tables?
    
    0. Create temporary tables tmp_farms, tmp_crops and tmp_deliveries,
    which don't have id columns.
    1. Truncate the three temporary tables
    2. Insert into the temp tables a "set" of prod data.
    3. Call a stored procedure in the dev database that does INSERT INTO
    ..., using RETURNING to get the relevant id values for the
    subsequent tables.
    4. goto 1.

On 10/4/23 21:15, Dow Drake wrote:

I see.  That would definitely work, but part of this for me is to get a better understanding of PostgreSQL's capabilities.  I'm going to keep working on a minimal solution that deletes no records from the dev database, and only inserts the required records.

On Wed, Oct 4, 2023 at 6:58 PM Ron <ronljohnsonjr@xxxxxxxxx> wrote:

Ah.  We'd truncate all of the dev tables, then load a "slice" (for example, accounts 10000 to 19999, and all associated records from downstream tables; lots and lots of views!!) from the prod database.

On 10/4/23 20:50, Dow Drake wrote:

Thanks for the reply, Ron!

I'm not sure I see how to make your suggestion work, though.  Suppose I dump the three tables to CSV as you suggest (and write a script to extract the relevant records from those CSV dumps in the correct order).  It might be that in the dev database, the next generated key values are 199 for farm's id, 2145 for crop's id and 10242 for deliveries' id.  The databases are independent.

Just inserting the records in the same order doesn't take care of setting the foreign key values correctly -- does it?  I think I'm really looking for a solution more along the lines of the link in my original post.

Best,

Dow

On Wed, Oct 4, 2023 at 6:26 PM Ron <ronljohnsonjr@xxxxxxxxx> wrote:

Frame challenge: why can't you just "\copy to" the dev database tables in the correct order, to satisfy foreign key requirements?

On 10/4/23 18:59, Dow Drake wrote:

Hi,

I'm trying to write a postgresql script to replicate a hierarchical structure in a live database into my development database, where I can debug and test more easily.  I can extract the data from the live database that needs to be inserted, but I'm having trouble writing the insertion script

Here's a simplified version of the problem I'm trying to solve:

There are three tables: farms, crops and deliveries where a farm has many crops and a crop has many deliveries.

create table farms (

   id bigint NOT NULL GENERATED BY DEFAULT AS IDENTITY,

   name character varying(30)

);

create table crops (

   id bigint NOT NULL GENERATED BY DEFAULT AS IDENTITY,

   farm_id bigint not null

   name character varying(30)

);

create table deliveries (

   id bigint NOT NULL GENERATED BY DEFAULT AS IDENTITY,

   crop_id bigint not null

   ticket character varying(30)

);

I want to insert a farm record, then insert two crops associated with that farm, then insert two deliveries for each of the the two crops so that in the end, my tables look like this:

farms

id     name

1      'Happy Valley Farm'

crops

id     farm_id    name

1        1         'corn'

2        1         'wheat'

delvieries

id       crop_id    ticket

1         1          '3124'

2         2          '3127'

3         1          '3133'

4         2          '3140'

It's important that the deliveries get assigned to the right crops.  I think this post: https://dba.stackexchange.com/questions/199916

gets close to what I need, but I haven't been able to figure out how to adapt it to multiple records.

Thanks for any help on this!

--
Born in Arizona, moved to Babylonia.

--
Born in Arizona, moved to Babylonia.

--
Born in Arizona, moved to Babylonia.