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chore: Warn on generated columns #448

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chore: Warn on generated columns #448

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ea4a976
Warn on generated columns
caike Nov 10, 2025
a63e1f3
Simplify checking for generated columns.
caike Nov 20, 2025
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36 changes: 34 additions & 2 deletions etl/src/replication/client.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -803,7 +803,8 @@ impl PgReplicationClient {
/// Retrieves schema information for all columns in a table.
///
/// If a publication is specified, only columns included in that publication
/// will be returned.
/// will be returned. Generated columns are always excluded since they are not
/// supported in PostgreSQL logical replication.
async fn get_column_schemas(
&self,
table_id: TableId,
Expand Down Expand Up @@ -831,6 +832,19 @@ impl PgReplicationClient {
join direct_parent dp on con.conrelid = dp.parent_oid
where con.contype = 'p'
group by con.conname
),
-- Identify generated columns for warning purposes
generated_cols as (
select
c.relname as table_name,
string_agg(a.attname, ', ' order by a.attnum) as generated_column_names
from pg_class c
join pg_attribute a on a.attrelid = c.oid
where c.oid = {table_id}
and a.attnum > 0
and not a.attisdropped
and a.attgenerated != ''
group by c.relname
)
select
a.attname,
Expand All @@ -847,7 +861,9 @@ impl PgReplicationClient {
where a.attname = any(pk.pk_column_names)
) then true
else false
end as primary
end as primary,
(select table_name from generated_cols) as gen_table_name,
(select generated_column_names from generated_cols) as gen_columns
from pg_attribute a
left join pg_index i
on a.attrelid = i.indrelid
Expand All @@ -865,6 +881,8 @@ impl PgReplicationClient {
);

let mut column_schemas = vec![];
let mut warned_about_generated = false;

for message in self.client.simple_query(&column_info_query).await? {
if let SimpleQueryMessage::Row(row) = message {
let name = Self::get_row_value::<String>(&row, "attname", "pg_attribute").await?;
Expand All @@ -876,6 +894,20 @@ impl PgReplicationClient {
let primary =
Self::get_row_value::<String>(&row, "primary", "pg_index").await? == "t";

// Check for generated columns and warn once per table
if !warned_about_generated
&& let Some(gen_columns) = row.try_get("gen_columns")?
&& let Some(table_name) = row.try_get("gen_table_name")?
{
warn!(
"Table '{}' contains generated columns ({}) that will NOT be replicated. \
Generated columns are not supported in PostgreSQL logical replication and will \
be excluded from the ETL schema. These columns will NOT appear in the destination.",
table_name, gen_columns
);
warned_about_generated = true;
}

let typ = convert_type_oid_to_type(type_oid);

column_schemas.push(ColumnSchema {
Expand Down