Bug:  Inject data statistics to simulate plan generation on actual TPCDS data
Status: Resolved | Priority: Major | Resolution: Fixed
Created: 07/Aug/20 10:04
Affects Version/s: 3.1.0

`TPCDSQuerySuite` currently computes plans with empty TPCDS tables, then checks if plans can be generated correctly. But, the generated plans can be different from actual ones because the input tables are empty (e.g., the plans always use broadcast-hash joins, but actual ones use sort-merge joins for larger tables). To mitigate the issue, this ticket targets at defining data statistics constants extracted from generated TPCDS data in `TPCDSTableStats`, then injects the statistics via `spark.sessionState.catalog.alterTableStats` when defining TPCDS tables in `TPCDSQuerySuite`.

Please see a link below about how to extract the table statistics:
 - https://gist.github.com/maropu/f553d32c323ee803d39e2f7fa0b5a8c3

For example, the generated plans of TPCDS `q2` are different with/without this fix:
{code:java}
==== w/ this fix: q2 ====
== Physical Plan ==
* Sort (43)
+- Exchange (42)
 +- * Project (41)
 +- * SortMergeJoin Inner (40)
 :- * Sort (28)
 : +- Exchange (27)
 : +- * Project (26)
 : +- * BroadcastHashJoin Inner BuildRight (25)
 : :- * HashAggregate (19)
 : : +- Exchange (18)
 : : +- * HashAggregate (17)
 : : +- * Project (16)
 : : +- * BroadcastHashJoin Inner BuildRight (15)
 : : :- Union (9)
 : : : :- * Project (4)
 : : : : +- * Filter (3)
 : : : : +- * ColumnarToRow (2)
 : : : : +- Scan parquet default.web_sales (1)
 : : : +- * Project (8)
 : : : +- * Filter (7)
 : : : +- * ColumnarToRow (6)
 : : : +- Scan parquet default.catalog_sales (5)
 : : +- BroadcastExchange (14)
 : : +- * Project (13)
 : : +- * Filter (12)
 : : +- * ColumnarToRow (11)
 : : +- Scan parquet default.date_dim (10)
 : +- BroadcastExchange (24)
 : +- * Project (23)
 : +- * Filter (22)
 : +- * ColumnarToRow (21)
 : +- Scan parquet default.date_dim (20)
 +- * Sort (39)
 +- Exchange (38)
 +- * Project (37)
 +- * BroadcastHashJoin Inner BuildRight (36)
 :- * HashAggregate (30)
 : +- ReusedExchange (29)
 +- BroadcastExchange (35)
 +- * Project (34)
 +- * Filter (33)
 +- * ColumnarToRow (32)
 +- Scan parquet default.date_dim (31)
==== w/o this fix: q2 ====
== Physical Plan ==
* Sort (40)
+- Exchange (39)
 +- * Project (38)
 +- * BroadcastHashJoin Inner BuildRight (37)
 :- * Project (26)
 : +- * BroadcastHashJoin Inner BuildRight (25)
 : :- * HashAggregate (19)
 : : +- Exchange (18)
 : : +- * HashAggregate (17)
 : : +- * Project (16)
 : : +- * BroadcastHashJoin Inner BuildRight (15)
 : : :- Union (9)
 : : : :- * Project (4)
 : : : : +- * Filter (3)
 : : : : +- * ColumnarToRow (2)
 : : : : +- Scan parquet default.web_sales (1)
 : : : +- * Project (8)
 : : : +- * Filter (7)
 : : : +- * ColumnarToRow (6)
 : : : +- Scan parquet default.catalog_sales (5)
 : : +- BroadcastExchange (14)
 : : +- * Project (13)
 : : +- * Filter (12)
 : : +- * ColumnarToRow (11)
 : : +- Scan parquet default.date_dim (10)
 : +- BroadcastExchange (24)
 : +- * Project (23)
 : +- * Filter (22)
 : +- * ColumnarToRow (21)
 : +- Scan parquet default.date_dim (20)
 +- BroadcastExchange (36)
 +- * Project (35)
 +- * BroadcastHashJoin Inner BuildRight (34)
 :- * HashAggregate (28)
 : +- ReusedExchange (27)
 +- BroadcastExchange (33)
 +- * Project (32)
 +- * Filter (31)
 +- * ColumnarToRow (30)
 +- Scan parquet default.date_dim (29)
 {code}