Setting the parameter MaxStatementCacheSize in firebird.conf file #8569
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Hello ! Please, tell me what changes may occur in the program's operation with the DB under Firebird 5.0 when connecting the parameter MaxStatementCacheSize with the value set to 0 ? Thanks ! |
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Replies: 2 comments 12 replies
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The statement caches stores the prepared plan for a specific statement text. So, simplified, if you prepare a statement, the server will check if it already has a plan for that statement text (and some other details), and if so, it uses that instead of preparing the whole plan anew. If the statement is not already in the cache, it will prepare it, and if possible store it in the cache. In other words, if the cache size is 0, nothing is ever cached, so each call to prepare will prepare the statement anew, instead of being able to reuse the information resulting from a previous prepare. That is basically the same behaviour as in older versions that did not have a statement cache. Why do you think it would lead to program failures? |
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I clarified to be sure. |
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@mrotteveel when the cache is disabled, it gets compiling new statements producing a much bigger leak. When the cache is enabled, it keeps getting a request instance of a existing statement, and there is a limit for that. |
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Thanks, I had somehow assumed that it would result in separate requests that are a clone of the cached one (or something like that), not literally using the same request. |
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Internally there is Statement (reused) and request (cloned). |
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Not exactly "cloned", each concurrent execution is a new request. Used and inactive ones, may be reused. |
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Interestingly, I have the feeling I've been told this before, but I forgot :) |
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The statement caches stores the prepared plan for a specific statement text. So, simplified, if you prepare a statement, the server will check if it already has a plan for that statement text (and some other details), and if so, it uses that instead of preparing the whole plan anew. If the statement is not already in the cache, it will prepare it, and if possible store it in the cache.
In other words, if the cache size is 0, nothing is ever cached, so each call to prepare will prepare the statement anew, instead of being able to reuse the information resulting from a previous prepare. That is basically the same behaviour as in older versions that did not have a statement cache.
Why do you…