Migration Safety¶

DBWarden classifies migration changes using the Safety enum:

from dbwarden.engine.safety import Safety

assert Safety.SAFE == "SAFE"
assert Safety.INFO == "INFO"
assert Safety.WARN == "WARN"
assert Safety.CRITICAL == "CRITICAL"

Safety Classification by Object Type¶

Tables & Columns¶

Change Type	Severity	Flag Required
Add column	`INFO`	None
Drop column	`WARNING`	`--force`
Change column type (safe)	`INFO`	None
Change column type (warn)	`WARNING`	`--force`
Change column type (critical)	`WARNING`	`--force`
Change column comment	`INFO`	None
Change nullable (SET/DROP NOT NULL)	`INFO`	None
Change default (SET/DROP DEFAULT)	`INFO`	None
Add autoincrement	`INFO`	None
Remove autoincrement	`WARNING`	`--force`
Change PG column meta (storage, compression, collation)	`WARNING`	`--force`
Rename column	`WARNING`	`--force`

Table Properties¶

Change Type	Severity	Flag Required
Change fillfactor	`INFO`	None
Change tablespace	`WARNING`	`--force`
Change inheritance	`WARNING`	`--force`
Change exclude constraints	`WARNING`	`--force`
Change table comment	`INFO`	None
Change object type (logged/unlogged)	`WARNING`	`--force`
Change ON COMMIT	`WARNING`	`--force`

Indexes¶

Change Type	Severity	Flag Required
Add index	`INFO`	None
Drop index	`WARNING`	`--force`
Change index expression / columns	`WARNING`	`--force`
Add/drop INCLUDE column	`INFO`	None
Change index storage parameters	`INFO`	None
Change index tablespace	`WARNING`	`--force`

Constraints¶

Change Type	Severity	Flag Required
Add FK	`INFO`	None
Drop FK	`WARNING`	`--force`
Change FK options	`WARNING`	`--force`
Add unique constraint	`INFO`	None
Drop unique constraint	`WARNING`	`--force`
Add check constraint	`INFO`	None
Drop check constraint	`WARNING`	`--force`
Add exclude constraint	`INFO`	None
Drop exclude constraint	`WARNING`	`--force`
Change constraint deferrability	`INFO`	None

Sequences¶

Change Type	Severity	Flag Required
Add sequence	`INFO`	None
Drop sequence	`WARNING`	`--force`
Change sequence options (start, increment, etc.)	`WARNING`	`--force`

Types¶

Change Type	Severity	Flag Required
Add enum value	`INFO`	None
Add enum type	`INFO`	None
Drop enum type	`WARNING`	`--force`
Add domain	`INFO`	None
Drop domain	`WARNING`	`--force`
Change domain definition	`WARNING`	`--force`
Add composite type	`INFO`	None
Drop composite type	`WARNING`	`--force`
Change composite type columns	`WARNING`	`--force`

Functions & Procedures¶

Change Type	Severity	Flag Required
Add function	`INFO`	None
Drop function	`WARNING`	`--force`
Change function body	`WARNING`	`--force`
Add procedure	`INFO`	None
Drop procedure	`WARNING`	`--force`

Triggers¶

Change Type	Severity	Flag Required
Add trigger	`INFO`	None
Drop trigger	`WARNING`	`--force`
Change trigger timing/events	`WARNING`	`--force`
Add constraint trigger	`INFO`	None
Drop constraint trigger	`WARNING`	`--force`

Roles & Grants¶

Change Type	Severity	Flag Required
Add role	`INFO`	None
Drop role	`WARNING`	`--force`
Change role options	`WARNING`	`--force`
Add grant	`INFO`	None
Revoke grant	`WARNING`	`--force`
Add default privilege	`INFO`	None
Revoke default privilege	`WARNING`	`--force`

Event Triggers¶

Change Type	Severity	Flag Required
Add event trigger	`INFO`	None
Drop event trigger	`WARNING`	`--force`
Change event trigger tags	`INFO`	None

Extended Statistics¶

Change Type	Severity	Flag Required
Add extended statistic	`INFO`	None
Drop extended statistic	`WARNING`	`--force`
Change kinds / columns	`WARNING`	`--force`
Change statistics target	`INFO`	None

Views¶

Change Type	Severity	Flag Required
Add view	`INFO`	None
Drop view	`WARNING`	`--force`
Change view query	`WARNING`	`--force`
Refresh materialized view	`INFO`	None
Change view schema	`WARNING`	`--force`

Schemas¶

Change Type	Severity	Flag Required
Add schema	`INFO`	None
Drop schema	`WARNING`	`--force`

RLS & Policies¶

Change Type	Severity	Flag Required
Enable RLS	`INFO`	None
Disable RLS	`WARNING`	`--force`
Force RLS	`INFO`	None
Add policy	`INFO`	None
Drop policy	`INFO`	None
Change policy expression	`INFO`	None

Partitions¶

Change Type	Severity	Flag Required
Add partition	`INFO`	None
Detach partition	`WARNING`	`--force`
Change partition strategy	`CRITICAL`	`--force`

Safe / Warn / Critical Type Changes¶

Safe Type Changes (INFO)¶

Conversion	Example
`VARCHAR(n)` → `VARCHAR(m)` (widening)	`VARCHAR(50)` → `VARCHAR(100)`
`VARCHAR` → `TEXT`	`VARCHAR` → `TEXT`
Storing to same type family	No change
`TIMESTAMP` → `TIMESTAMPTZ`	Adding timezone info
`json` → `jsonb`	JSON to binary JSON
Adding `NOT NULL` when column has no NULLs	Safe when data validates

Warn Type Changes (WARNING)¶

Conversion	Example
`VARCHAR(n)` → `VARCHAR(m)` (narrowing)	`VARCHAR(100)` → `VARCHAR(50)`
`INTEGER` → `BIGINT`	Widening (safe in PG, uses USING)
`BIGINT` → `INTEGER`	Narrowing (potential data loss)
`TEXT` → `VARCHAR(n)`	Truncation risk
`NUMERIC(p,s)` → `NUMERIC(p',s')` with precision loss	May truncate
Any type change that requires USING	Needs manual verification

Critical Type Changes (CRITICAL)¶

Conversion	Example
Dropping the only column of a table	Always critical
Removing enum values	Not supported by PostgreSQL
Changing partition key columns	Requires full table rewrite + data migration
Converting from `SETOF`/`TABLE` return type	Schema breakage