You can store a SQL query with prepare.
db=# prepare posts_search as select title from posts limit 5;
PREPARE
Call the method with execute.
db=# execute posts_search;
title
-----------------------------------
Hello World!
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(5 rows)
Deallocate the query with deallocate, and you can set it again.
db=# deallocate posts_search;
DEALLOCATE
db=# prepare posts_search as select title from posts limit 10;
PREPARE