lidavidm commented on code in PR #54360:
URL: https://github.com/apache/arrow/pull/54360#discussion_r4331631799
##########
cpp/src/arrow/flight/sql/types.h:
##########
@@ -849,6 +849,20 @@ struct ARROW_FLIGHT_SQL_EXPORT SqlInfoOptions {
/// escape syntax is supported.
SQL_STORED_FUNCTIONS_USING_CALL_SYNTAX_SUPPORTED = 576,
+ /// Retrieves a UTF-8 string containing a Substrait dialect: a YAML
+ /// document, conforming to the Substrait dialect schema, that lists the
+ /// types, relations, expressions and function signatures the server
+ /// accepts in a Substrait plan. Should only be returned if
+ /// FLIGHT_SQL_SERVER_SUBSTRAIT is true. Its absence means that the server
+ /// does not describe which part of Substrait it accepts.
Review Comment:
Can we just link to the Substrait docs?
##########
format/FlightSql.proto:
##########
@@ -833,6 +833,36 @@ enum SqlInfo {
* - true: if invoking user-defined or vendor functions using the stored
procedure escape syntax is supported.
*/
SQL_STORED_FUNCTIONS_USING_CALL_SYNTAX_SUPPORTED = 576;
+
+ /*
+ * Retrieves a UTF-8 string containing a Substrait dialect: a YAML document,
+ * conforming to the Substrait dialect schema (text/dialect_schema.yaml in
the
+ * Substrait repository), that lists the types, relations, expressions and
+ * function signatures the server accepts in a Substrait plan.
+ *
+ * A plan that only uses what the dialect lists is expected to be accepted;
+ * one that uses anything else may be rejected. The dialect should only be
+ * returned if FLIGHT_SQL_SERVER_SUBSTRAIT is true. Its absence means that
the
+ * server does not describe which part of Substrait it accepts, not that it
+ * accepts all of it.
+ *
+ * A dialect can be tens of kilobytes. A client that retrieves it repeatedly
+ * can retrieve SQL_SUBSTRAIT_DIALECT_HASH first and only retrieve this value
+ * when the hash has changed.
+ */
Review Comment:
Same here.
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