feat: left join

[aceforeverd]

The result of a LEFT OUTER JOIN (or simply LEFT JOIN) for two from_items always retains all rows of the left from_item in the JOIN operation, even if no rows in the right from_item satisfy the join predicate.

Syntax

LEFT [OUTER] JOIN

Example:

SELECT * FROM t1 LEFT JOIN t2 on t1.key = t2.key

Online Requirements

A simple LEFT JOIN can not online directly, since it always outputs a table. But LEFT JOIN can ack as a subquery inside other queries, currently we only consider LAST JOIN (maybe work on WINDOW or WINDOW UNION later)

LEFT JOIN can be the right source of a LAST JOIN query, format of

SELECT ... FROM request LAST JOIN 
(SELECT ... FROM t2 LEFT JOIN t3 ON ...) tx ON ...`

• table t3 must index optimized by the LEFT JOIN condition
• table t2 must index optimized by the outer side LEFT JOIN condition

[codecov]

Codecov Report

Attention: 311 lines in your changes are missing coverage. Please review.

Comparison is base (2fb650a) 40.14% compared to head (eab8951) 75.39%.

Files	Patch %	Lines
hybridse/src/vm/runner_builder.cc	65.14%	206 Missing ⚠️
hybridse/src/vm/catalog_wrapper.cc	57.35%	29 Missing ⚠️
hybridse/src/vm/cluster_task.cc	75.90%	20 Missing ⚠️
hybridse/include/vm/mem_catalog.h	50.00%	15 Missing ⚠️
hybridse/include/vm/catalog.h	0.00%	12 Missing ⚠️
hybridse/src/vm/catalog_wrapper.h	76.08%	11 Missing ⚠️
hybridse/src/vm/generator.cc	95.28%	5 Missing ⚠️
hybridse/src/vm/cluster_task.h	92.00%	4 Missing ⚠️
hybridse/src/vm/runner.cc	76.47%	4 Missing ⚠️
...ybridse/examples/toydb/src/tablet/tablet_catalog.h	80.00%	2 Missing ⚠️
... and 2 more

Additional details and impacted files

@@              Coverage Diff              @@
##               main    #3576       +/-   ##
=============================================
+ Coverage     40.14%   75.39%   +35.25%     
  Complexity      635      635               
=============================================
  Files           191      727      +536     
  Lines         11207   130597   +119390     
  Branches       1317     1317               
=============================================
+ Hits           4499    98468    +93969     
- Misses         6417    31838    +25421     
  Partials        291      291               

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