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Using the PG Gem for Postgresql in Ruby, how would you check to see if a prepared statement already exists?

newUserNameHere
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  • What do you mean as "prepared statements in Ruby" ? Ruby statements do not need any preparation. – Sergey Bolgov May 29 '13 at 01:00
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    @SergeyBolgov: *prepared statements* is database terminology: http://rubydoc.info/gems/pg/PG/Connection#prepare-instance_method and http://www.postgresql.org/docs/current/static/sql-prepare.html – mu is too short May 29 '13 at 01:05
  • Correct. "prepared statement" is a database terminology. So the question "check if prepared statement already exists in Ruby" makes no sense. Probably, the OP wanted to ask about "prepared statement in Rails+Postgres". The question needs clarification. – Sergey Bolgov May 29 '13 at 01:19
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    @SergeyBolgov: They're using accessing PostgreSQL using Ruby's `pg` gem and they want to know how to check if a particular prepared statement already exists. Seems pretty clear to me. – mu is too short May 29 '13 at 01:58
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    is this what you are looking for: http://stackoverflow.com/questions/13967333/prepared-statements-already-exists, or you can use http://www.postgresql.org/docs/9.2/interactive/view-pg-prepared-statements.html – akonsu May 29 '13 at 02:01
  • I restated the question for clarification. I'm not able to find the answer for this anywhere. Thank you akonsu, although I didn't ask how to deallocate a prepared statement using the PG Gem in ruby, that was a problem I ran into yesterday. Up vote for helpfulness :) – newUserNameHere May 29 '13 at 12:13
  • Actually here they asked the same question: http://stackoverflow.com/questions/13967333/prepared-statements-already-exists But only got an answer showing how to deallocate the statement that already exists, not to check if it's already there. – newUserNameHere May 29 '13 at 12:15

2 Answers2

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You can query the pg_prepared_statements view to see if the name is used: http://www.postgresql.org/docs/9.2/interactive/view-pg-prepared-statements.html

Credit goes to akonsu who answered in comments.

newUserNameHere
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0

You can also do it by catching the error that you get when you call describe_prepared 

statement_exists = true
begin 
  connection.describe_prepared(statement_name)
rescue PG::InvalidSqlStatementName
  statement_exists = false
end
bob
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