backward-compatible-schema-changeslisted

# Backward-Compatible Schema Changes ## What Making database schema changes that don't break existing application code. The application continues working without any code changes, even though the database structure has been modified. ## Why In production systems, you can't deploy database changes and application changes at the exact same millisecond. There's always a window where the old app code runs against the new schema (or vice versa). Backward-compatible changes eliminate this risk. ## How ### Column renames with preserved parameter names ```sql -- The procedure parameter keeps the OLD name CREATE OR REPLACE PROCEDURE public."AddApplicant"( ... "p_vertirnarytechorassistant" boolean, -- old spelling preserved ... ) AS $$ BEGIN INSERT INTO public."Applicant" ( ... "the clientTechOrAssistant", -- new spelling in column ref ... ) VALUES ( ... p_vertirnarytechorassistant, -- old spelling in param ref (no quotes) ... ); END; $$ LANGUAGE plpgsql; ``` The application calls: ```sql CALL public."AddApplicant"( p_vertirnarytechorassistant => true -- still works! ); ``` ### The principle | Layer | What Changed | What Stayed | |-------|-------------|-------------| | Table column name | `"VertirnaryTechOrAssistant"` -> `"the clientTechOrAssistant"` | Data, type, constraints | | Procedure body | Quoted column refs updated | Everything else | | Procedure signature | Nothing | Parameter names, type