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postgresql integration: Throw errors instead of assuming array_ndim == 1

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Ryan Jacobs 2023-12-06 11:54:45 -08:00
parent 17aacda9e5
commit b57340bde2
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1 changed files with 31 additions and 29 deletions
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60
src/Databases/PostgreSQL/fetchPostgreSQLTableStructure.cpp
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@ -222,40 +222,42 @@ PostgreSQLTableStructure::ColumnsInfoPtr readNamesAndTypesList(
{
const auto & name_and_type = columns[i];
/// NOTE: If the relation is empty, then array_ndims returns NULL.
/// If this is the case, then assume dimensions=1. This covers most
/// use cases, but will be incorrect for empty tables with
/// multi-dimension arrays. The other solutions would be to drop
/// support for empty tables OR attempt fallback to a discovered
/// array_ndims CHECK constraint.
int dimensions;
/// If the relation is empty, then array_ndims returns NULL.
/// ClickHouse cannot support this use case.
if (isTableEmpty(tx, postgres_table))
{
dimensions = 1;
}
else
{
/// All rows must contain the same number of dimensions.
/// 1 is ok. If number of dimensions in all rows is not the same -
/// such arrays are not able to be used as ClickHouse Array at all.
///
/// Assume dimensions=1 for empty arrays.
auto postgres_column = doubleQuoteString(name_and_type.name);
pqxx::result result{tx.exec(fmt::format(
"SELECT {} IS NULL, COALESCE(array_ndims({}), 1) "
"FROM {} LIMIT 1;",
postgres_column,
postgres_column,
postgres_table))};
throw Exception(ErrorCodes::BAD_ARGUMENTS, "PostgreSQL relation containing arrays cannot be empty: {}", postgres_table);
/// Nullable(Array) is not supported.
auto is_null = result[0][0].as<bool>();
if (is_null)
throw Exception(ErrorCodes::BAD_ARGUMENTS, "PostgreSQL array cannot be NULL. Column: {}", postgres_column);
/// All rows must contain the same number of dimensions.
/// 1 is ok. If number of dimensions in all rows is not the same -
/// such arrays are not able to be used as ClickHouse Array at all.
///
/// For empty arrays, array_ndims([]) will return NULL.
auto postgres_column = doubleQuoteString(name_and_type.name);
pqxx::result result{tx.exec(fmt::format(
"SELECT {} IS NULL, array_ndims({}) "
"FROM {} LIMIT 1;",
postgres_column,
postgres_column,
postgres_table))};
dimensions = result[0][1].as<int>();
/// Nullable(Array) is not supported.
auto is_null_array = result[0][0].as<bool>();
if (is_null_array)
throw Exception(ErrorCodes::BAD_ARGUMENTS, "PostgreSQL array cannot be NULL: {}.{}", postgres_table, postgres_column);
/// Cannot infer dimension of empty arrays.
auto is_empty_array = result[0][1].is_null();
if (is_empty_array)
{
throw Exception(
ErrorCodes::BAD_ARGUMENTS,
"PostgreSQL cannot infer dimensions of an empty array: {}.{}",
postgres_table,
postgres_column);
}
int dimensions = result[0][1].as<int>();
/// It is always 1d array if it is in recheck.
DataTypePtr type = assert_cast<const DataTypeArray *>(name_and_type.type.get())->getNestedType();
while (dimensions--)