From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Jelte Fennema <me(at)jeltef(dot)nl> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Support prepared statement invalidation when result types change |
Date: | 2024-07-24 15:39:56 |
Message-ID: | 1238027.1721835596@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Jelte Fennema <me(at)jeltef(dot)nl> writes:
> The cached plan for a prepared statements can get invalidated when DDL
> changes the tables used in the query, or when search_path changes.
> ...
> However, we would throw an error if the the result of the query is of a
> different type than it was before:
> ERROR: cached plan must not change result type
Yes, this is intentional.
> This patch starts to allow a prepared statement to continue to work even
> when the result type changes.
What this is is a wire protocol break. What if the client has
previously done a Describe Statement on the prepared statement?
We have no mechanism for notifying it that that information is
now falsified. The error is thrown to prevent us from getting
into a situation where we'd need to do that.
regards, tom lane
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