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Support for weak binding views to allow dropping of underlying objects #3806

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@R4hul04 R4hul04 commented Jun 5, 2025

Description

Currently, Babelfish only supports strong binding for views, which prevents dropping or altering referenced objects when views depend on them. This behavior differs from SQL Server, which by default allows dropping underlying tables or views unless WITH SCHEMABINDING is explicitly specified.
With this change, Babelfish now supports configurable view binding modes:

  1. Strong binding (default): Prevents dropping referenced objects if views depend on them
  2. Weak binding: Allows dropping of referenced objects

This feature aligns Babelfish more closely with SQL Server's behavior, providing greater flexibility
Key aspects include:

  • A new GUC parameter babelfishpg_tsql.weak_view_binding to control the default binding behavior (default is false)
  • Support for explicit WITH SCHEMABINDING to create strongly bound views regardless of the GUC setting
  • Ability to create weakly bound views by default when the GUC is enabled
  • Proper handling of ALTER VIEW operations in both binding modes

In SQL Server, views are weakly bound by default, allowing underlying objects to be dropped or altered. With our implementation, users can now choose between SQL Server's default behavior (weak binding) or the previously enforced behavior (strong binding).

Important Limitation :

This implementation currently only addresses DROP operations on tables, views as well as ALTER operations on views. ALTER TABLE operations (such as dropping columns or changing data types) are still restricted when dependent views exist, regardless of binding mode. This differs from SQL Server's behavior, where weak binding also allows ALTER operations on referenced objects.

Issues Resolved

BABEL-1660

Test Scenarios Covered

  • Use case based -

  • Boundary conditions -

  • Arbitrary inputs -

  • Negative test cases -

  • Minor version upgrade tests -

  • Major version upgrade tests -

  • Performance tests -

  • Tooling impact -

  • Client tests -

Check List

  • Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is under the terms of the Apache 2.0 and PostgreSQL licenses, and grant any person obtaining a copy of the contribution permission to relicense all or a portion of my contribution to the PostgreSQL License solely to contribute all or a portion of my contribution to the PostgreSQL open source project.

For more information on following Developer Certificate of Origin and signing off your commits, please check here.

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coveralls commented Jun 5, 2025

Pull Request Test Coverage Report for Build 15688661888

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

Details

  • 465 of 491 (94.7%) changed or added relevant lines in 4 files are covered.
  • 490 unchanged lines in 7 files lost coverage.
  • Overall coverage increased (+0.2%) to 75.703%

Changes Missing Coverage Covered Lines Changed/Added Lines %
contrib/babelfishpg_tsql/src/hooks.c 454 480 94.58%
Files with Coverage Reduction New Missed Lines %
contrib/babelfishpg_tsql/src/tsqlUnsupportedFeatureHandler.cpp 1 88.33%
contrib/babelfishpg_tsql/src/pl_exec-2.c 14 82.52%
contrib/babelfishpg_tsql/src/hooks.c 27 86.19%
contrib/babelfishpg_tsql/src/catalog.c 74 86.67%
contrib/babelfishpg_common/src/collation.c 83 79.02%
contrib/babelfishpg_tsql/src/pltsql_coerce.c 132 86.57%
contrib/babelfishpg_tsql/src/collation.c 159 73.88%
Totals Coverage Status
Change from base Build 15464616681: 0.2%
Covered Lines: 49338
Relevant Lines: 65173

💛 - Coveralls

@R4hul04 R4hul04 requested a review from forestkeeper June 5, 2025 23:53
@R4hul04 R4hul04 requested a review from kuntalghosh June 9, 2025 23:55
Rahul Parande added 3 commits June 10, 2025 01:02
Signed-off-by: Rahul Parande <[email protected]>
SCHEMABINDING clause in view definitions

Signed-off-by: Rahul Parande <[email protected]>
@R4hul04 R4hul04 marked this pull request as ready for review June 11, 2025 00:02
DefineCustomBoolVariable("babelfishpg_tsql.weak_view_binding",
gettext_noop("Sets the default binding mode for views."),
gettext_noop("When false (default), views have strong binding which prevents dropping referenced"
"objects. When true, views have weak binding which allows it."),
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"When true, views have weak binding which allows dropping referenced objects."

@@ -1,5 +1,5 @@
#include "postgres.h"

#include "guc.h"
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guc.h not supposed to be at this place.

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@R4hul04 R4hul04 Jun 13, 2025

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Removed the header file declaration

@@ -18,14 +18,17 @@
#include "catalog/pg_attrdef_d.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_db_role_setting.h"
#include "catalog/pg_depend.h"
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For .h , pls add a comment of which dependent need to introduce a new include .h

@@ -169,6 +174,12 @@ static void transform_pivot_clause(ParseState *pstate, SelectStmt *stmt);
static void transform_unpivot_clause(ParseState *pstate, SelectStmt *stmt);
static bool transform_unpivot_clause_recursive(Node **node, List **measure_cols, List **unpivot_src_cols);
static List* filter_star_targetlist_for_unpivot(ParseState *pstate, SelectStmt *stmt, List **source_cols);
static bool babelfish_view_repair_hook(Query *parsetree);
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If it's a hook implement, the name of this function should not ends with hook.

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Changed to repair_broken_views()

Rahul Parande added 3 commits June 13, 2025 20:22
@R4hul04 R4hul04 requested a review from tanscorpio7 June 16, 2025 17:14
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3 participants