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https://issues.apache.org/jira/browse/PHOENIX-2306?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas D'Silva resolved PHOENIX-2306.
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Resolution: Fixed
> Expose additional statistics in the explain plan to allow better cost
> estimation
> ---------------------------------------------------------------------------------
>
> Key: PHOENIX-2306
> URL: https://issues.apache.org/jira/browse/PHOENIX-2306
> Project: Phoenix
> Issue Type: New Feature
> Environment: 4.5.1
> Reporter: Alok Singh
> Priority: Minor
>
> In a mailing list converstation, James described the phoenix APIs that can be
> used to derive cost estimates.
> {noformat}
> Yes, you could calculate an estimate for this information, but it isn't
> currently exposed through JDBC or through the explain plan (which would be a
> good place for it to live). You'd need to dip down to the implementation to
> get it. Something like this:
> PhoenixStatement statement =
> connection.createStatement().unwrap(PhoenixStatement.class);
> ResultSet rs = statement.executeQuery("EXPLAIN SELECT ...");
> QueryPlan plan = statement.getQueryPlan();
> List<KeyRange> ranges = plan.getSplits();
> Each KeyRange in ranges will be going over a configurable amount of bytes
> (determined by phoenix.stats.guidepost.width and/or
> phoenix.stats.guidepost.per.region), so a simple worst case estimate would be
> to multiply the ranges.size() by this config value (using a default of
> QueryServicesOptions.DEFAULT_STATS_GUIDEPOST_WIDTH_BYTES or 300MB). If the
> query is a point lookup (which you can check with
> plan.getContext().getScanRanges().isPointLookup()), then the cost would be
> ranges.size() * average_row_size.
> Since these aren't exposed APIs, they're subject to change. Please file a
> JIRA if you're interested in helping figure out what the "official" APIs for
> this should be.
> {noformat}
> Ideally, these statistics should be returned as part of the explain plan.
> That would allow the end users of phoenix to use standard JDBC tooling to get
> at this information.
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