Freeze the inserted tuples during CTAS?

[Paul Guo]

Here is the simple patch,

diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index dce882012e..0391699423 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -552,7 +552,7 @@ intorel_startup(DestReceiver *self, int operation, 
TupleDesc typeinfo)
    myState->rel = intoRelationDesc;
    myState->reladdr = intoRelationAddr;
    myState->output_cid = GetCurrentCommandId(true);
-   myState->ti_options = TABLE_INSERT_SKIP_FSM;
+   myState->ti_options = TABLE_INSERT_SKIP_FSM | TABLE_INSERT_FROZEN;

MatView code already does this and COPY does this if specified. I’m not sure how
does the community think about this. Actually personally I expect more about the
all-visible setting due to TABLE_INSERT_FROZEN since I could easier use index 
only scan
if we create an index and table use CTAS, else people have to use index only 
scan
after vacuum. If people do not expect freeze could we at least introduce a 
option to
specify the visibility during inserting?

Regards,
Paul