Hi,
In the past I've found the error message in cases such as this somewhat
less helpful than it could be:
=# CREATE TABLE qqq (a int);
=# CREATE UNIQUE INDEX IF NOT EXISTS qqq_a_idx ON qqq(a);
=# ALTER TABLE qqq ALTER COLUMN a TYPE json USING NULL;
ERROR: data type json has no default operator class for access method
"btree"
HINT: You must specify an operator class for the index or define a
default operator class for the data type.
The attached patch adds a CONTEXT line to index and constraint rebuilds,
e.g:
CONTEXT: while rebuilding index qqq_a_idx
Any feedback welcome.
.m