Enable fast default for domains with non-volatile constraints Previously, ALTER TABLE ADD COLUMN always forced a table rewrite when the column type was a domain with constraints (CHECK or NOT NULL), even if the default value satisfied those constraints. This was because contain_volatile_functions() considers CoerceToDomain immutable, so the code conservatively assumed any constrained domain might fail.
Improve this by using soft error handling (ErrorSaveContext) to evaluate the CoerceToDomain expression at ALTER TABLE time. If the default value passes the domain's constraints, the value is stored as a "missing" attribute default and no table rewrite is needed. If the constraint check fails, we fall back to a table rewrite, preserving the historical behavior that constraint violations are only raised when the table actually contains rows. Domains with volatile constraint expressions always require a table rewrite since the constraint result could differ per evaluation and cannot be cached. Author: Jian He <[email protected]> Reviewed-by: Tom Lane <[email protected]> Reviewed-by: Andrew Dunstan <[email protected]> Reviewed-by: Viktor Holmberg <[email protected]> Discussion: https://postgr.es/m/cacjufxe_+izbr1i49k_ahigpppwltji6km8nosc7fwvkdem...@mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/a0b6ef29a51818a4073a5f390ed10ef6453d5c11 Modified Files -------------- src/backend/commands/tablecmds.c | 59 ++++++++++++++++++++--------- src/backend/executor/execExpr.c | 35 ++++++++++++++++- src/include/executor/executor.h | 2 + src/test/regress/expected/fast_default.out | 61 ++++++++++++++++++++++++++++++ src/test/regress/sql/fast_default.sql | 51 +++++++++++++++++++++++++ 5 files changed, 190 insertions(+), 18 deletions(-)
