Hello hackers,
I have a feature suggestion to optimize the creation of a partial
index. In some cases, it is possible to skip a full table scan. For
example:
BEGIN;
ALTER TABLE test ADD COLUMN (newcol int);
CREATE INDEX newindex ON test(newcol) WHERE newcol IS NOT NULL;
COMMIT;
In this case, the values of all columns in the new table will be NULL,
and there is no point in checking the conditions for each row. The
same optimization can be done for default values in NOT NULL columns.
How complex would a patch with this optimization be? Will it be
necessary to add any attributes to the table metadata, or can we check
that the previous command was CREATE TABLE when creating an index?