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Gautam Parai <gparai@maprtech.com>
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on 21 Aug 14
DRILL-1328: Support table statistics - Part 2
Add support for avg row-width and major type statistics.
Parallelize the ANALYZE implementatio… Show more
DRILL-1328: Support table statistics - Part 2

Add support for avg row-width and major type statistics.

Parallelize the ANALYZE implementation and stats UDF implementation to improve stats collection performance.

Update/fix rowcount, selectivity and ndv computations to improve plan costing.

Add options for configuring collection/usage of statistics.

Add new APIs and implementation for stats writer (as a precursor to Drill Metastore APIs).

Fix several stats/costing related issues identified while running TPC-H nad TPC-DS queries.

Add support for CPU sampling and nested scalar columns.

Add more testcases for collection and usage of statistics and fix remaining unit/functional test failures.

Thanks to Venki Korukanti (@vkorukanti) for the description below (modified to account for new changes). He graciously agreed to rebase the patch to latest master, fixed few issues and added few tests.

FUNCS: Statistics functions as UDFs:

Separate

Currently using FieldReader to ensure consistent output type so that Unpivot doesn't get confused. All stats columns should be Nullable, so that stats functions can return NULL when N/A.

* custom versions of "count" that always return BigInt

* HyperLogLog based NDV that returns BigInt that works only on VarChars

* HyperLogLog with binary output that only works on VarChars

OPS: Updated protobufs for new ops

OPS: Implemented StatisticsMerge

OPS: Implemented StatisticsUnpivot

ANALYZE: AnalyzeTable functionality

* JavaCC syntax more-or-less copied from LucidDB.

* (Basic) AnalyzePrule: DrillAnalyzeRel -> UnpivotPrel StatsMergePrel FilterPrel(for sampling) StatsAggPrel ScanPrel

ANALYZE: Add getMetadataTable() to AbstractSchema

USAGE: Change field access in QueryWrapper

USAGE: Add getDrillTable() to DrillScanRelBase and ScanPrel

* since ScanPrel does not inherit from DrillScanRelBase, this requires adding a DrillTable to the constructor

* This is done so that a custom ReflectiveRelMetadataProvider can access the DrillTable associated with Logical/Physical scans.

USAGE: Attach DrillStatsTable to DrillTable.

* DrillStatsTable represents the data scanned from a corresponding ".stats.drill" table

* In order to avoid doing query execution right after the ".stats.drill" table is found, metadata is not actually collected until the MaterializationVisitor is used.

** Currently, the metadata source must be a string (so that a SQL query can be created). Doing this with a table is probably more complicated.

** Query is set up to extract only the most recent statistics results for each column.

closes #729

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