Jefffrey commented on code in PR #5343:
URL: https://github.com/apache/arrow-datafusion/pull/5343#discussion_r1130598377
##########
datafusion/sql/src/expr/identifier.rs:
##########
@@ -160,3 +180,243 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
)))
}
}
+
+// (relation, column name)
+fn form_identifier(idents: &[String]) -> Result<(Option<TableReference>,
&String)> {
+ match idents.len() {
+ 1 => Ok((None, &idents[0])),
+ 2 => Ok((
+ Some(TableReference::Bare {
+ table: (&idents[0]).into(),
+ }),
+ &idents[1],
+ )),
+ 3 => Ok((
+ Some(TableReference::Partial {
+ schema: (&idents[0]).into(),
+ table: (&idents[1]).into(),
+ }),
+ &idents[2],
+ )),
+ 4 => Ok((
+ Some(TableReference::Full {
+ catalog: (&idents[0]).into(),
+ schema: (&idents[1]).into(),
+ table: (&idents[2]).into(),
+ }),
+ &idents[3],
+ )),
+ _ => Err(DataFusionError::Internal(format!(
+ "Incorrect number of identifiers: {}",
+ idents.len()
+ ))),
+ }
+}
+
+fn search_dfschema<'ids, 'schema>(
+ ids: &'ids [String],
+ schema: &'schema DFSchema,
+) -> Option<(&'schema DFField, &'ids [String])> {
+ generate_schema_search_terms(ids).find_map(|(qualifier, column,
nested_names)| {
+ let field = schema.field_with_name(qualifier.as_ref(), column).ok();
+ field.map(|f| (f, nested_names))
+ })
+}
+
+// Possibilities we search with, in order from top to bottom for each len:
+//
+// len = 2:
+// 1. (table.column)
+// 2. (column).nested
+//
+// len = 3:
+// 1. (schema.table.column)
+// 2. (table.column).nested
+// 3. (column).nested1.nested2
+//
+// len = 4:
+// 1. (catalog.schema.table.column)
+// 2. (schema.table.column).nested1
+// 3. (table.column).nested1.nested2
+// 4. (column).nested1.nested2.nested3
+//
+// len = 5:
+// 1. (catalog.schema.table.column).nested
+// 2. (schema.table.column).nested1.nested2
+// 3. (table.column).nested1.nested2.nested3
+// 4. (column).nested1.nested2.nested3.nested4
+//
+// len > 5:
+// 1. (catalog.schema.table.column).nested[.nestedN]+
+// 2. (schema.table.column).nested1.nested2[.nestedN]+
+// 3. (table.column).nested1.nested2.nested3[.nestedN]+
+// 4. (column).nested1.nested2.nested3.nested4[.nestedN]+
+fn generate_schema_search_terms(
+ ids: &[String],
+) -> impl Iterator<Item = (Option<TableReference>, &String, &[String])> {
+ // take at most 4 identifiers to form a Column to search with
+ // - 1 for the column name
+ // - 0 to 3 for the TableReference
+ let bound = ids.len().min(4);
+ // search terms from most specific to least specific
+ (0..bound).rev().map(|i| {
+ let nested_names_index = i + 1;
+ let qualifier_and_column = &ids[0..nested_names_index];
+ let (relation, column_name) =
form_identifier(qualifier_and_column).unwrap();
+ (relation, column_name, &ids[nested_names_index..])
+ })
+}
+
+#[cfg(test)]
+mod test {
+ use super::*;
+
+ #[test]
+ // testing according to documentation of generate_schema_search_terms
function
+ // where ensure generated search terms are in correct order with correct
values
+ fn test_generate_schema_search_terms() -> Result<()> {
+ type ExpectedItem = (
+ Option<TableReference<'static>>,
+ &'static str,
+ &'static [&'static str],
+ );
+ fn assert_vec_eq(
+ expected: Vec<ExpectedItem>,
+ actual: Vec<(Option<TableReference>, &String, &[String])>,
+ ) {
+ for (expected, actual) in expected.into_iter().zip(actual) {
+ assert_eq!(expected.0, actual.0, "qualifier");
+ assert_eq!(expected.1, actual.1, "column name");
+ assert_eq!(expected.2, actual.2, "nested names");
+ }
+ }
+
+ let actual = generate_schema_search_terms(&[]).collect::<Vec<_>>();
+ assert!(actual.is_empty());
+
+ let ids = vec!["a".to_string()];
+ let actual = generate_schema_search_terms(&ids).collect::<Vec<_>>();
+ let expected: Vec<ExpectedItem> = vec![(None, "a", &[])];
+ assert_vec_eq(expected, actual);
+
+ let ids = vec!["a".to_string(), "b".to_string()];
+ let actual = generate_schema_search_terms(&ids).collect::<Vec<_>>();
+ let expected: Vec<ExpectedItem> = vec![
+ (Some(TableReference::bare("a")), "b", &[]),
+ (None, "a", &["b"]),
+ ];
+ assert_vec_eq(expected, actual);
+
+ let ids = vec!["a".to_string(), "b".to_string(), "c".to_string()];
+ let actual = generate_schema_search_terms(&ids).collect::<Vec<_>>();
+ let expected: Vec<ExpectedItem> = vec![
+ (Some(TableReference::partial("a", "b")), "c", &[]),
+ (Some(TableReference::bare("a")), "b", &["c"]),
+ (None, "a", &["b", "c"]),
+ ];
+ assert_vec_eq(expected, actual);
+
+ let ids = vec![
+ "a".to_string(),
+ "b".to_string(),
+ "c".to_string(),
+ "d".to_string(),
+ ];
+ let actual = generate_schema_search_terms(&ids).collect::<Vec<_>>();
+ let expected: Vec<ExpectedItem> = vec![
+ (Some(TableReference::full("a", "b", "c")), "d", &[]),
+ (Some(TableReference::partial("a", "b")), "c", &["d"]),
+ (Some(TableReference::bare("a")), "b", &["c", "d"]),
+ (None, "a", &["b", "c", "d"]),
+ ];
+ assert_vec_eq(expected, actual);
+
+ let ids = vec![
+ "a".to_string(),
+ "b".to_string(),
+ "c".to_string(),
+ "d".to_string(),
+ "e".to_string(),
+ ];
+ let actual = generate_schema_search_terms(&ids).collect::<Vec<_>>();
+ let expected: Vec<ExpectedItem> = vec![
+ (Some(TableReference::full("a", "b", "c")), "d", &["e"]),
+ (Some(TableReference::partial("a", "b")), "c", &["d", "e"]),
+ (Some(TableReference::bare("a")), "b", &["c", "d", "e"]),
+ (None, "a", &["b", "c", "d", "e"]),
+ ];
+ assert_vec_eq(expected, actual);
+
+ let ids = vec![
+ "a".to_string(),
+ "b".to_string(),
+ "c".to_string(),
+ "d".to_string(),
+ "e".to_string(),
+ "f".to_string(),
+ ];
+ let actual = generate_schema_search_terms(&ids).collect::<Vec<_>>();
+ let expected: Vec<ExpectedItem> = vec![
+ (Some(TableReference::full("a", "b", "c")), "d", &["e", "f"]),
+ (
+ Some(TableReference::partial("a", "b")),
+ "c",
+ &["d", "e", "f"],
+ ),
+ (Some(TableReference::bare("a")), "b", &["c", "d", "e", "f"]),
+ (None, "a", &["b", "c", "d", "e", "f"]),
+ ];
+ assert_vec_eq(expected, actual);
+
+ Ok(())
+ }
+
+ #[test]
+ fn test_form_identifier() -> Result<()> {
+ let err = form_identifier(&[]).expect_err("empty identifiers didn't
fail");
+ let expected = "Internal error: Incorrect number of identifiers: 0. \
Review Comment:
I made it `Internal` error since `form_identifier(...)` is a private
function that is only used by `sql_compound_identifier_to_expr(...)` and
`generate_schema_search_terms(...)` which already check that it doesn't pass an
invalid list in (hence calls unwrap on it).
So in normal usage this error can't ever occur. I made it return an error
type just in case in future the method is used elsewhere. I'll update the
comments a bit to reflect this
Edit: comments updated
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