wangyum opened a new pull request, #37267:
URL: https://github.com/apache/spark/pull/37267
### What changes were proposed in this pull request?
This PR improves join stats estimation if one side can keep uniqueness. A
common case is:
```sql
SELECT i_item_sk ss_item_sk
FROM item,
(SELECT DISTINCT iss.i_brand_id brand_id,
iss.i_class_id class_id,
iss.i_category_id category_id
FROM item iss) x
WHERE i_brand_id = brand_id
AND i_class_id = class_id
AND i_category_id = category_id
```
In this case, the row count of the join will definitely not expand.
Before this PR:
```
== Optimized Logical Plan ==
Project [i_item_sk#4 AS ss_item_sk#54], Statistics(sizeInBytes=370.8 MiB,
rowCount=3.24E+7)
+- Join Inner, (((i_brand_id#11 = brand_id#51) AND (i_class_id#13 =
class_id#52)) AND (i_category_id#15 = category_id#53)),
Statistics(sizeInBytes=1112.3 MiB, rowCount=3.24E+7)
:- Project [i_item_sk#4, i_brand_id#11, i_class_id#13, i_category_id#15],
Statistics(sizeInBytes=4.6 MiB, rowCount=2.02E+5)
: +- Filter ((isnotnull(i_brand_id#11) AND isnotnull(i_class_id#13)) AND
isnotnull(i_category_id#15)), Statistics(sizeInBytes=84.6 MiB, rowCount=2.02E+5)
: +- Relation
spark_catalog.default.item[i_item_sk#4,i_item_id#5,i_rec_start_date#6,i_rec_end_date#7,i_item_desc#8,i_current_price#9,i_wholesale_cost#10,i_brand_id#11,i_brand#12,i_class_id#13,i_class#14,i_category_id#15,i_category#16,i_manufact_id#17,i_manufact#18,i_size#19,i_formulation#20,i_color#21,i_units#22,i_container#23,i_manager_id#24,i_product_name#25]
parquet, Statistics(sizeInBytes=85.2 MiB, rowCount=2.04E+5)
+- Aggregate [brand_id#51, class_id#52, category_id#53], [brand_id#51,
class_id#52, category_id#53], Statistics(sizeInBytes=2.6 MiB, rowCount=1.37E+5)
+- Project [i_brand_id#62 AS brand_id#51, i_class_id#64 AS
class_id#52, i_category_id#66 AS category_id#53], Statistics(sizeInBytes=3.9
MiB, rowCount=2.02E+5)
+- Filter ((isnotnull(i_brand_id#62) AND isnotnull(i_class_id#64))
AND isnotnull(i_category_id#66)), Statistics(sizeInBytes=84.6 MiB,
rowCount=2.02E+5)
+- Relation
spark_catalog.default.item[i_item_sk#55,i_item_id#56,i_rec_start_date#57,i_rec_end_date#58,i_item_desc#59,i_current_price#60,i_wholesale_cost#61,i_brand_id#62,i_brand#63,i_class_id#64,i_class#65,i_category_id#66,i_category#67,i_manufact_id#68,i_manufact#69,i_size#70,i_formulation#71,i_color#72,i_units#73,i_container#74,i_manager_id#75,i_product_name#76]
parquet, Statistics(sizeInBytes=85.2 MiB, rowCount=2.04E+5)
```
After this PR:
```
== Optimized Logical Plan ==
Project [i_item_sk#4 AS ss_item_sk#54], Statistics(sizeInBytes=2.3 MiB,
rowCount=2.02E+5)
+- Join Inner, (((i_brand_id#11 = brand_id#51) AND (i_class_id#13 =
class_id#52)) AND (i_category_id#15 = category_id#53)),
Statistics(sizeInBytes=7.0 MiB, rowCount=2.02E+5)
:- Project [i_item_sk#4, i_brand_id#11, i_class_id#13, i_category_id#15],
Statistics(sizeInBytes=4.6 MiB, rowCount=2.02E+5)
: +- Filter ((isnotnull(i_brand_id#11) AND isnotnull(i_class_id#13)) AND
isnotnull(i_category_id#15)), Statistics(sizeInBytes=84.6 MiB, rowCount=2.02E+5)
: +- Relation
spark_catalog.default.item[i_item_sk#4,i_item_id#5,i_rec_start_date#6,i_rec_end_date#7,i_item_desc#8,i_current_price#9,i_wholesale_cost#10,i_brand_id#11,i_brand#12,i_class_id#13,i_class#14,i_category_id#15,i_category#16,i_manufact_id#17,i_manufact#18,i_size#19,i_formulation#20,i_color#21,i_units#22,i_container#23,i_manager_id#24,i_product_name#25]
parquet, Statistics(sizeInBytes=85.2 MiB, rowCount=2.04E+5)
+- Aggregate [brand_id#51, class_id#52, category_id#53], [brand_id#51,
class_id#52, category_id#53], Statistics(sizeInBytes=2.6 MiB, rowCount=1.37E+5)
+- Project [i_brand_id#62 AS brand_id#51, i_class_id#64 AS
class_id#52, i_category_id#66 AS category_id#53], Statistics(sizeInBytes=3.9
MiB, rowCount=2.02E+5)
+- Filter ((isnotnull(i_brand_id#62) AND isnotnull(i_class_id#64))
AND isnotnull(i_category_id#66)), Statistics(sizeInBytes=84.6 MiB,
rowCount=2.02E+5)
+- Relation
spark_catalog.default.item[i_item_sk#55,i_item_id#56,i_rec_start_date#57,i_rec_end_date#58,i_item_desc#59,i_current_price#60,i_wholesale_cost#61,i_brand_id#62,i_brand#63,i_class_id#64,i_class#65,i_category_id#66,i_category#67,i_manufact_id#68,i_manufact#69,i_size#70,i_formulation#71,i_color#72,i_units#73,i_container#74,i_manager_id#75,i_product_name#76]
parquet, Statistics(sizeInBytes=85.2 MiB, rowCount=2.04E+5)
```
### Why are the changes needed?
Plan more broadcast joins to improve query performance.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Unit test.
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