alamb commented on code in PR #4995:
URL: https://github.com/apache/arrow-datafusion/pull/4995#discussion_r1082633781
##########
datafusion/core/src/datasource/listing/table.rs:
##########
@@ -67,6 +67,10 @@ pub struct ListingTableConfig {
pub file_schema: Option<SchemaRef>,
/// Optional `ListingOptions` for the to be created `ListingTable`.
pub options: Option<ListingOptions>,
+ /// Optional default is false, if temporary is true, then it means that
+ /// we will create a temporary table for select * from `xxx.file`
+ /// or describe 'xxx.file', the temporary table will be registered to the
schema
+ pub temporary_file: bool,
Review Comment:
💯 for the comments. Thank you @xiaoyong-z
I think the term `temporary_files` often means something different --
specifically files in `/tmp` or similar -- so it may be confusing to use the
same term.
What would you think about using a different term than `temporary`? Perhaps
`ephemeral` would be appropriate.
##########
datafusion/core/tests/sqllogictests/test_files/describe.slt:
##########
@@ -0,0 +1,43 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+
+# http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+
+##########
+# Describe internal tables
+##########
+
+statement ok
+set datafusion.catalog.information_schema = true
+
+statement ok
+CREATE external table aggregate_simple(c1 real, c2 double, c3 boolean) STORED
as CSV WITH HEADER ROW LOCATION 'tests/data/aggregate_simple.csv';
+
+query C1
+DESCRIBE aggregate_simple;
Review Comment:
This test works on master -- I don't think it needs the changes in this PR
```
(arrow_dev) alamb@MacBook-Pro-8:~/Software/arrow-datafusion/datafusion/core$
datafusion-cli
DataFusion CLI v16.0.0
❯ CREATE external table aggregate_simple(c1 real, c2 double, c3 boolean)
STORED as CSV WITH HEADER ROW LOCATION 'tests/data/aggregate_simple.csv';
0 rows in set. Query took 0.005 seconds.
❯
DESCRIBE aggregate_simple;
+-------------+-----------+-------------+
| column_name | data_type | is_nullable |
+-------------+-----------+-------------+
| c1 | Float32 | NO |
| c2 | Float64 | NO |
| c3 | Boolean | NO |
+-------------+-----------+-------------+
3 rows in set. Query took 0.002 seconds.
❯
```
##########
datafusion/expr/src/logical_plan/plan.rs:
##########
@@ -1625,6 +1637,15 @@ pub struct Prepare {
pub input: Arc<LogicalPlan>,
}
+/// Describe a file
Review Comment:
What would you think about making this more general `DescribeTable` and
rather than taking a file_path it would have a `table_provider`? I think then
we wouldn't have to special case describe for file / table -- instead
DataFusion could always create `DescribeTable`
The query in terms of information_schema is sort of a hack in the first
place. What you have started here with an actual LogicalPlan variant I think is
much better 👍
##########
datafusion/sql/src/statement.rs:
##########
@@ -385,25 +385,32 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
let DescribeTable { table_name } = statement;
let where_clause = object_name_to_qualifier(&table_name);
+ let table_str_name = object_name_to_table_str_name(&table_name);
let table_ref = object_name_to_table_reference(table_name)?;
- // check if table_name exists
- let _ = self
+ let table_source = self
.schema_provider
.get_table_provider((&table_ref).into())?;
- if self.has_table("information_schema", "tables") {
- let sql = format!(
- "SELECT column_name, data_type, is_nullable \
- FROM information_schema.columns WHERE
{where_clause};"
- );
- let mut rewrite = DFParser::parse_sql(&sql)?;
- self.statement_to_plan(rewrite.pop_front().unwrap())
+ if !table_source.is_temporary_file() {
Review Comment:
I wonder if we can figure out a way to avoid special casing here. Perhaps we
can always create a DescribeTable plan?
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