Fix tsql_stat_get_activity() and tsql_read_current_status() to consider only valid tds backends

[shah-nirmit]

Description

Fixed the tsql_read_current_status to increment LocalNumBackends only when it has a valid pid, also fixed tsql_stat_get_activity to use numbackends as calculated by TDS extension insteand of pg_stat_activity.

Issue

When idle Babelfish sessions are killed one-by-one, after killing a certain number of sessions (usually 8-9), other yet-unkilled sessions suddenly disappear from sys.dm_exec_sessions. They still do appear in pg_stat_activity.

RCA

There seems to be 2 issues

1. We are incorrectly setting numLocalBackends(Static variable) for TDS in function tdsstat_read_current_status Check link vs how pg does it (Basic if logic bug)

2. We are using pg_stat_fetch_numbackends Function in tsql_stat_get_activity , which seems wrong because the status Array for pg vs tds BackendStatus are different so are the numLocalBackends variable. Check Link

These bugs seem to exist from this commit onwards

Issues Resolved

BABEL-5219

Test Scenarios Covered

• Use case based - YES

• Boundary conditions -

• Arbitrary inputs -

• Negative test cases -

• Minor version upgrade tests -

• Major version upgrade tests -

• Performance tests -

• Tooling impact -

• Client tests -

Signed-off-by: Nirmit Shah nirmisha@amazon.com

Check List

• [ ] Commits are signed per the DCO using --signoff

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[coveralls]

Pull Request Test Coverage Report for Build 10714050807

Warning: This coverage report may be inaccurate.

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Details

• 9 of 9 (100.0%) changed or added relevant lines in 3 files are covered.
• 439 unchanged lines in 11 files lost coverage.
• Overall coverage increased (+0.006%) to 74.232%

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Files with Coverage Reduction	New Missed Lines	%
contrib/babelfishpg_tds/src/backend/tds/tds.c	2	92.84%
contrib/babelfishpg_tds/src/backend/tds/tdstypeio.c	4	87.13%
contrib/babelfishpg_tsql/src/schemacmds.c	4	92.54%
contrib/babelfishpg_tsql/src/hooks.c	14	80.35%
contrib/babelfishpg_common/src/varchar.c	24	85.96%
contrib/babelfishpg_tsql/src/extendedproperty.c	26	94.83%
contrib/babelfishpg_tds/src/backend/tds/tdsrpc.c	37	71.45%
contrib/babelfishpg_tsql/src/catalog.c	51	87.2%
contrib/babelfishpg_tsql/src/dbcmds.c	64	74.85%
contrib/babelfishpg_tsql/src/pltsql_coerce.c	87	80.56%
<!--	Total:	439		-->

Totals
Change from base Build 10665086919:	0.006%
Covered Lines:	44683
Relevant Lines:	60194

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💛 - Coveralls