Prepare to support non-tables in publications

This by itself doesn't change any functionality but prepares the way for having relations other than base tables in publications. Make arrangements for COPY handling the initial table sync. For non-tables we have to use COPY (SELECT ...) instead of directly copying from the table, but then we have to take care to omit generated columns from the column list. Also, remove a hardcoded reference to relkind = 'r' and rely on the publisher to send only what it can actually publish, which will be correct even in future cross-version scenarios. Reviewed-by: Amit Langote <amitlangote09@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/CA+HiwqH=Y85vRK3mOdjEkqFK+E=ST=eQiHdpj43L=_eJMOOznQ@mail.gmail.com

Author: petere

src/backend/replication/logical/tablesync.c

@@ -639,8 +639,8 @@ fetch_remote_table_info(char *nspname, char *relname,
 WalRcvExecResult *res;
 StringInfoData cmd;
 TupleTableSlot *slot;
-OidtableRow[2] = {OIDOID, CHAROID};
-OidattrRow[4] = {TEXTOID, OIDOID, INT4OID, BOOLOID};
+OidtableRow[] = {OIDOID, CHAROID, CHAROID};
+OidattrRow[] = {TEXTOID, OIDOID, INT4OID, BOOLOID};
 boolisnull;
 intnatt;
 
@@ -649,16 +649,15 @@ fetch_remote_table_info(char *nspname, char *relname,
 
 /* First fetch Oid and replica identity. */
 initStringInfo(&cmd);
-appendStringInfo(&cmd, "SELECT c.oid, c.relreplident"
+appendStringInfo(&cmd, "SELECT c.oid, c.relreplident, c.relkind"
  " FROM pg_catalog.pg_class c"
  " INNER JOIN pg_catalog.pg_namespace n"
  " ON (c.relnamespace = n.oid)"
  " WHERE n.nspname = %s"
- " AND c.relname = %s"
- " AND c.relkind = 'r'",
+ " AND c.relname = %s",
  quote_literal_cstr(nspname),
  quote_literal_cstr(relname));
-res = walrcv_exec(wrconn, cmd.data, 2, tableRow);
+res = walrcv_exec(wrconn, cmd.data, lengthof(tableRow), tableRow);
 
 if (res->status != WALRCV_OK_TUPLES)
 ereport(ERROR,
@@ -675,6 +674,8 @@ fetch_remote_table_info(char *nspname, char *relname,
 Assert(!isnull);
 lrel->replident = DatumGetChar(slot_getattr(slot, 2, &isnull));
 Assert(!isnull);
+lrel->relkind = DatumGetChar(slot_getattr(slot, 3, &isnull));
+Assert(!isnull);
 
 ExecDropSingleTupleTableSlot(slot);
 walrcv_clear_result(res);
@@ -696,7 +697,7 @@ fetch_remote_table_info(char *nspname, char *relname,
  lrel->remoteid,
  (walrcv_server_version(wrconn) >= 120000 ? "AND a.attgenerated = ''" : ""),
  lrel->remoteid);
-res = walrcv_exec(wrconn, cmd.data, 4, attrRow);
+res = walrcv_exec(wrconn, cmd.data, lengthof(attrRow), attrRow);
 
 if (res->status != WALRCV_OK_TUPLES)
 ereport(ERROR,
@@ -765,8 +766,25 @@ copy_table(Relation rel)
 
 /* Start copy on the publisher. */
 initStringInfo(&cmd);
-appendStringInfo(&cmd, "COPY %s TO STDOUT",
- quote_qualified_identifier(lrel.nspname, lrel.relname));
+if (lrel.relkind == RELKIND_RELATION)
+appendStringInfo(&cmd, "COPY %s TO STDOUT",
+ quote_qualified_identifier(lrel.nspname, lrel.relname));
+else
+{
+/*
+ * For non-tables, we need to do COPY (SELECT ...), but we can't just
+ * do SELECT * because we need to not copy generated columns.
+ */
+appendStringInfo(&cmd, "COPY (SELECT ");
+for (int i = 0; i < lrel.natts; i++)
+{
+appendStringInfoString(&cmd, quote_identifier(lrel.attnames[i]));
+if (i < lrel.natts - 1)
+appendStringInfoString(&cmd, ", ");
+}
+appendStringInfo(&cmd, " FROM %s) TO STDOUT",
+ quote_qualified_identifier(lrel.nspname, lrel.relname));
+}
 res = walrcv_exec(wrconn, cmd.data, 0, NULL);
 pfree(cmd.data);
 if (res->status != WALRCV_OK_COPY_OUT)

src/include/replication/logicalproto.h

@@ -49,6 +49,7 @@ typedef struct LogicalRepRelation
 char **attnames;/* column names */
 Oid *atttyps;/* column types */
 charreplident;/* replica identity */
+charrelkind;/* remote relation kind */
 Bitmapset *attkeys;/* Bitmap of key columns */
 } LogicalRepRelation;