Previously, a query string returned from pg_ivm_get_querydef
did not include column names specified when IMMV was defined
by create_immv. This caused failures in maintenance of MIN/MAX
aggregate views whose columns had alias names.
It is fixed by rewriting the result column name in the parse tree
using the view's tuple descriptor prior to calling pg_get_querydef
for PG15 or higher, or specifying the tuple descriptor to
get_query_def for PG14 or earlier.
Per sub-queries support, a test for join with subquery is added.
In passing, the order of tests are fixed with according to that in pgsql-ivm.
Also, some other tests related to aggregates and sub-queries are added.
In order to re-calculate min/max values for groups where the min
or max value is deleted, we need the view query definition in string
form. However, pg_get_viewdef cannot be used for this purpose because
IMMV's defenition is in pg_ivm_immv but not pg_rewrite. Therefore,
we have to convert query definition in pg_ivm_immv to query
definition string. We can use pg_get_querydef in PG15, but we cannot
in PG14 or earlier, so we use codes in ruleutil.c copied from PG13
or PG14 depending versions.
When a base table is truncated, the view content will be empty if the
view definition query does not contain an aggregate without a GROUP clause.
Therefore, such views can be truncated.
Aggregate views without a GROUP clause always have one row. Therefore,
if a base table is truncated, the view will not be empty and will contain
a row with NULL value (or 0 for count()). So, in this case, we refresh the
view instead of truncating it.
Built-in count, sum, avg are supported. We have not supported min/max
yet, but will support in future.
When an IMMV with any aggregates are defined, additional columns
are created for each aggregate function. Although such columns are
"hidden" in pgsql-ivm version, they are always visible for users
in the extension version.
