[GitHub] [calcite] chunweilei commented on a change in pull request #2366: [CALCITE-4526] Fixup the unparse's output of SqlSnapshot,when tableRel is a SqlAsOperator (jibiyr)

[GitBox <gi...@apache.org>]

chunweilei commented on a change in pull request #2366:
URL: https://github.com/apache/calcite/pull/2366#discussion_r592008165



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File path: core/src/main/java/org/apache/calcite/sql/SqlSnapshot.java
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@@ -127,10 +129,25 @@ private SqlSnapshotOperator() {
         int leftPrec,
         int rightPrec) {
       final SqlSnapshot snapshot = (SqlSnapshot) call;
-
-      snapshot.tableRef.unparse(writer, 0, 0);
-      writer.keyword("FOR SYSTEM_TIME AS OF");
-      snapshot.period.unparse(writer, 0, 0);
+      SqlNode tableRef = snapshot.tableRef;
+
+      if (tableRef instanceof SqlBasicCall
+          && ((SqlBasicCall) tableRef).getOperator() instanceof SqlAsOperator) {
+        SqlBasicCall basicCall = (SqlBasicCall) tableRef;
+        basicCall.operand(0).unparse(writer, 0, 0);
+        writer.setNeedWhitespace(true);
+        writeForSystemTimeAsOf(writer, snapshot);
+        writer.keyword("AS");
+        basicCall.operand(1).unparse(writer, 0, 0);
+      } else {
+        tableRef.unparse(writer, 0, 0);
+        writeForSystemTimeAsOf(writer, snapshot);
+      }
     }
   }
+
+  private static void writeForSystemTimeAsOf(SqlWriter writer, SqlSnapshot snapshot) {
+    writer.keyword("FOR SYSTEM_TIME AS OF");
+    snapshot.period.unparse(writer, 0, 0);

Review comment:
       Maybae it is better to put `writeForSystemTimeAsOf` in SqlSnapshotOperator.




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