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May 8, 2026
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Refine the column option docs #237

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37 changes: 17 additions & 20 deletions doc/pg_clickhouse.md
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Expand Up @@ -323,33 +323,30 @@ type of each column. The supported column options are:

```sql
CREATE FOREIGN TABLE hits (
watchid bigint OPTIONS(column_name 'WatchID'),
watchid bigint OPTIONS(column_name 'WatchID'),
javaenable smallint OPTIONS(column_name 'JavaEnable'),
title text OPTIONS(column_name 'Title')
title text OPTIONS(column_name 'Title')
) SERVER taxi_srv OPTIONS(table_name 'hits');
```

For [AggregateFunction Type] and [SimpleAggregateFunction Type] columns, map
the data type to the ClickHouse type passed to the function and specify the
name of the aggregate function via the appropriate column option:

* `AggregateFunction`: The name of the aggregate function applied to an
[AggregateFunction Type] column
* `SimpleAggregateFunction`: The name of the aggregate function applied to
an [SimpleAggregateFunction Type] column
[AggregateFunction Type] column. Map the data type to the ClickHouse type
passed to the function and specify the name of the aggregate function via
the appropriate column option and pg_clickhouse will automatically append
`Merge` to an aggregate function evaluating the column.

Example:

```sql
CREATE FOREIGN TABLE test (
column1 bigint OPTIONS(AggregateFunction 'uniq'),
column2 integer OPTIONS(AggregateFunction 'anyIf'),
column3 bigint OPTIONS(AggregateFunction 'quantiles(0.5, 0.9)')
) SERVER clickhouse_srv;
```
```sql
CREATE FOREIGN TABLE test (
column1 bigint OPTIONS(AggregateFunction 'uniq'),
column2 integer OPTIONS(AggregateFunction 'anyIf'),
column3 bigint OPTIONS(AggregateFunction 'quantiles(0.5, 0.9)')
) SERVER clickhouse_srv;
```

For columns with the `AggregateFunction` function, pg_clickhouse will
automatically append `Merge` to an aggregate function evaluating the column.
* `SimpleAggregateFunction`: The name of the aggregate function applied to
an [SimpleAggregateFunction Type] column. Map the data type to the
ClickHouse type passed to the function and specify the name of the
aggregate function via the appropriate column option.

### ALTER FOREIGN TABLE

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