Hi,
Currently, I have a problem. I am working on a project with generated columns.
I try to implement the generated column feature in the typeorm project. The
thing is, I don't want to drop and add a generated column every time the
application starts. Therefore I need a way to check whether a generated column
expression has changed.
With select generation_expression from information_schema."columns" c where
c.generation_expression is not null; I can retrieve the saved generation
expression. However, It seems like Postgres optimizes or changes it. Therefore,
it is different.
Example:
I add a column like this:
alter table company add tsv tsvector generated always as
(setweight(to_tsvector('german', coalesce(name, '')), 'A') ||
setweight(jsonb_to_tsvector('german', keywords::jsonb, '["string"]'),'A'))
stored;
Now if I try to retrieve the expression with select c.generation_expression
from information_schema."columns" c where c.column_name = 'tsv' and
c.table_name = 'company'; it is different.
Input expression:
setweight(to_tsvector('german', coalesce(title, '')), 'A') ||
setweight(to_tsvector('german', coalesce(description, '')), 'B');
What I got from postgres:
(setweight(to_tsvector('german'::regconfig, (COALESCE(name, ''::character
varying))::text), 'A'::"char") ||
setweight(jsonb_to_tsvector('german'::regconfig, keywords,
'["string"]'::jsonb), 'A'::"char"))
Postgres formats the query in some way. Is there any way to do this manually?
Like:
magic_function_to_format_sql(`setweight(to_tsvector('german', coalesce(title,
'')), 'A') || setweight(to_tsvector('german', coalesce(description, '')),
'B')`) Returns: (setweight(to_tsvector('german'::regconfig, (COALESCE(name,
''::character varying))::text), 'A'::"char") ||
setweight(jsonb_to_tsvector('german'::regconfig, keywords,
'["string"]'::jsonb), 'A'::"char"))
Then I could check if the saved expression is equal to the formatted one. I
tried to find information in the documentation. But I had no luck.
Best regards,
Nils Bergmann
