support join select

[valichek]

Please, review the changes, further directions required.

At the point this change will fix error from #26

ERROR: table `w` not available for query` for case

SELECT d.id, coalesce(w.w_count,0) as w_count FROM my_table AS d
LEFT JOIN LATERAL ( 
    SELECT count(*) as w_count FROM my_another_table WHERE d.id = ext_id AND deleted_at IS NULL
) w ON true
WHERE d.deleted_at IS NULL;

But another error comes out

table `d` not available for query

Following changes done in own commit being negotiable.
It looks like the only way to proceed is to pass tables used from top level here and join with ones parsed in validateSelectStmt(...)

The first thing that comes to my mind is to add top-level used tables to VetContext

type VetContext struct {
  Schema *schema.Db
  TablesUsed []TableUsed
}

It will go down through all the select statements in hierarchy. In order this to work properly used tables may be collected in ParsedResult.

Not much of test cases available in the project so maybe someone could point to the possible pitfalls of such decision.

[codecov-commenter]

Codecov Report

Patch coverage: 61.06% and project coverage change: -1.65 ⚠️

Comparison is base (f887b7a) 77.87% compared to head (c2ed7e2) 76.22%.

📣 This organization is not using Codecov’s GitHub App Integration. We recommend you install it so Codecov can continue to function properly for your repositories. Learn more

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #29      +/-   ##
==========================================
- Coverage   77.87%   76.22%   -1.65%     
==========================================
  Files           7        7              
  Lines         931      959      +28     
==========================================
+ Hits          725      731       +6     
- Misses        155      165      +10     
- Partials       51       63      +12     

Impacted Files	Coverage Δ
pkg/vet/vet.go	78.43% <60.43%> (-3.40%)	⬇️
pkg/schema/postgres.go	63.15% <63.63%> (-0.95%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[houqp]

The high level idea is we need to keep track of all the aliases definitions when parsing the queries, so I think your design is on the right track 👍

[valichek]

Latest commit introduced inner schema concept restricted to single query and protects original db schema from mutation. Also removed from Select queries call of getUsedTablesFromSelectStmt as redundant walking over the nodes to collect used tables - this moved to parseExpression(). If it looks fine we can proceed with more refactoring in validateUpdateStmt/validateInsertStmt,

[valichek]

@houqp I think this is ready

[houqp]

Thanks @valichek for the feature!