PostgreSQL 12 `quote_literal` function explanation - sql

Question

I want to understand how quote_literal() function works.
This is my table:
CREATE TABLE temp_emp (
id integer,
name text
);
INSERT INTO TEMP_EMP (id, name) VALUES (1, 'Super Pavel');
When I do:
SELECT * FROM "public".temp_emp WHERE name like '%Pavel%';
I have 1 row in result.
However, when I do:
SELECT * FROM "public".temp_emp WHERE name like quote_literal('%Pavel%');
I have 0 rows in result.
At the same time:
SELECT * FROM quote_literal('%Pavel%');
returns '%Pavel%'.
Could anyone explain why like '%Pavel%' and like quote_literal('%Pavel%') give different results?

Answer 1

The purpose of quote_literal() -- as explained in the documentation -- is to quote values for dynamic SQL. Dynamic SQL means that you are putting SQL into a string.
If you run this on different values, you will see that it includes the single quotes:
select str, '"' || quote_literal(str) || '"'
from (values ('abc'), ('abc def'), ('abc '' def')) v(str);
This returns:
abc "'abc'"
abc def "'abc def'"
abc ' def "'abc '' def'"
In particular, the single quotes are inside the string -- the double quotes are there too, but just to illustrate the boundaries of the string.
Clearly, although your data might have 'Pavel' embedded in them, none of your rows have 'Pavel' with single quotes.