DBZ-7351 Avoid child data snapshots from PostgreSQL parent tables

When PostgreSQL tables are configured with inheritance (INHERIT clause),
data is streamed by Debezium from the table where the data resides
(usually the child tables).

However, during the initial/incremental snapshot, Debezium selects all
data from the parent tables, including child data, which pushes
unexpected/duplicate data into the topics (all data from child tables).

Using a "SELECT ... FROM ONLY" retrieves only data from the current
table and avoids retrieving data from child tables.

Signed-off-by: Nicolas Payart <npayart@gmail.com>

debezium-connector-postgres/src/main/java/io/debezium/connector/postgresql/snapshot/QueryingSnapshotter.java

@@ -27,7 +27,7 @@ public void init(PostgresConnectorConfig config, OffsetState sourceInfo, SlotSta
     @Override
     public Optional<String> buildSnapshotQuery(TableId tableId, List<String> snapshotSelectColumns) {
         String query = snapshotSelectColumns.stream()
-                .collect(Collectors.joining(", ", "SELECT ", " FROM " + tableId.toDoubleQuotedString()));
+                .collect(Collectors.joining(", ", "SELECT ", " FROM ONLY " + tableId.toDoubleQuotedString()));
 
         return Optional.of(query);
     }

debezium-connector-postgres/src/test/java/io/debezium/connector/postgresql/CustomTestSnapshot.java

@@ -47,7 +47,7 @@ public Optional<String> buildSnapshotQuery(TableId tableId, List<String> snapsho
         }
         else {
             String query = snapshotSelectColumns.stream()
-                    .collect(Collectors.joining(", ", "SELECT ", " FROM " + tableId.toDoubleQuotedString()));
+                    .collect(Collectors.joining(", ", "SELECT ", " FROM ONLY " + tableId.toDoubleQuotedString()));
 
             return Optional.of(query);
         }