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https://issues.apache.org/jira/browse/CALCITE-906?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14940466#comment-14940466
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Julian Hyde commented on CALCITE-906:
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.bq Do we really want globally-unique statement ids?
We don't need globally unique. Just unique within a JdbcMeta (across all
connections, for the life of the JdbcMeta).
Also, we don't need to be able to look at a statement and discern its ID. We
generate one when it is created, and store it in the StatementHandle.
There are not going to be more than 2^31 statements in the lifetime of a
JdbcMeta, so we're OK.
> Avatica JdbcMeta statement IDs are not unique
> ---------------------------------------------
>
> Key: CALCITE-906
> URL: https://issues.apache.org/jira/browse/CALCITE-906
> Project: Calcite
> Issue Type: Bug
> Components: avatica
> Reporter: Jan Van Besien
> Assignee: Julian Hyde
> Attachments: CALCITE-906.patch
>
>
> There seems to be a concurrency-related problem with the statementId that is
> generated in the JdbcMeta#createStatement for statements in the
> statementCache.
> We use avatica to create a driver which uses the remote RPC protocol to wrap
> an existing jdbc driver on the server. We have a test which performs
> concurrent queries on multiple connections (using apache commons-pool) which
> fails often.
> If it fails, the following two things are always observed:
> * A java.lang.AssertionError on the assert in Meta#count(String connectionId,
> int statementId, long updateCount), resulting in the server to send a http
> 500.
> * When logging all used connectionId's and statementId's, I observe the same
> statementId to be re-used for different connectionId's.
> I don't know exactly how these two problems are related, but it looks like
> statementId's are supposed to be unique and currently they are not.
> The current approach is to use System.identityHashCode(statement) to
> calculate a statementId. Simply replacing this with a random int seems to
> solve the problem.
> Depending on what the actual uniqueness requirements for the statementId are,
> a UUID might be even better (but will have impact on the RPC) or an
> AtomicInteger.
> I'll attach a patch for the random int fix.
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