On 2/2/26 5:04 PM, Vitaly Davydov wrote:
1. Log into the WAL system catalog changes (tuples) suitable for logical
decoding (introduce a new wal_level = logical_ddl). I think, not all system
catalog changes are needed for decoding (not sure, we have to decode
pg_depend
changes).
2. Implement a decoder of system catalog changes, that can produce a
parse tree
using existing structures from parsenodes.h.
3. Based on the decoded parse tree, we can convert it into json or DDL SQL
statements in the output plugin. ParseTree to DDL SQL converter can be
built-in
into the core. Output plugin can decide which converter to use. DDL sql
can be
directly applied on the replica.
4. Another option is to create json/ddl-sql from system catalog changes
without
an intermediate representation, but, anyway, when we interpret system
catalog
changes we have to temporary save current data in some structures.
Parsenodes
is the already existing solution for it.
With this approach how do you intend to handle DDL changes which alter
data? To take a simple case we have the USING clause when altering a
column. Maybe it is a fine limitation to just not support it but I am
not convinced.
Andreas
