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I am having a two-column table trial(id serial, value text).

Then I use ALTER TABLE to change the data type of id to text, and still if I insert records like:

insert into trial(value) values('name');

Then serial is still getting incremented everytime I am adding rows into it. If I insert a row like

insert into trial values(111111111111....a very large number, 'name');

It still works and it still increments the serial counter.

My question is: why doesn't it overflow? Though the datatype of the column is text, the serial value would be still stored in a integer internally right? what is the data type of the variable that holds the serial value of a table(in psql's implementation) so that I can be sure that it would never overflow?

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  • What is the CREATE TABLE statement? Commented Sep 15, 2020 at 10:50
  • create table trial( id serial, value text); Commented Sep 15, 2020 at 10:52
  • Then you cannot store ids over 2147483647. Commented Sep 15, 2020 at 10:53
  • but explicitly providing a large id works Commented Sep 15, 2020 at 10:55
  • I don't believe that, if you really used serial. Commented Sep 15, 2020 at 11:01

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If you insert an explicit value into a column with a DEFAULT, the default value is not used. It does not matter that the value you enter is not a valid integer - it is a valid text, that is all that matters.

If you don't enter a value for id, PostgreSQL uses the sequence and converts the result to text.

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Will 2147483647 be the max value of the sequence?
Depends on how it is defined (\ds+ triall_id_seq).
Ok, thank you very much sir for investing so much of your precious time into my question.

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