[GitHub] [calcite] ILuffZhe commented on a diff in pull request #3274: [CALCITE-5688] Support TRUNCATE TABLE DDL statement in server module

["ILuffZhe (via GitHub)" <gi...@apache.org>]

ILuffZhe commented on code in PR #3274:
URL: https://github.com/apache/calcite/pull/3274#discussion_r1249095446


##########
server/src/main/java/org/apache/calcite/server/ServerDdlExecutor.java:
##########
@@ -182,6 +183,22 @@ static SqlNode renameColumns(@Nullable SqlNodeList columnList,
         null, null, null, null, null);
   }
 
+  static void erase(SqlIdentifier name, CalcitePrepare.Context context) {
+    // Directly clearing data is more efficient than executing SQL
+    final Pair<CalciteSchema, String> pair = schema(context, true, name);
+    final CalciteSchema calciteSchema = pair.left;
+    final String tblName = pair.right;
+    final Table table = calciteSchema
+        .getTable(tblName, context.config().caseSensitive())
+        .getTable();
+    if (table instanceof MutableArrayTable) {
+      MutableArrayTable mutableArrayTable = (MutableArrayTable) table;
+      mutableArrayTable.rows.clear();
+    } else {
+      throw new UnsupportedOperationException("Only MutableArrayTable support truncate");

Review Comment:
   May I ask why only MutableArrayTable is supported? ^_^



##########
core/src/main/codegen/templates/Parser.jj:
##########
@@ -4353,6 +4357,30 @@ SqlDrop SqlDrop() :
 }
 </#if>
 
+<#if (parser.truncateStatementParserMethods!default.parser.truncateStatementParserMethods)?size != 0>
+/**
+ * Parses a TRUNCATE TABLE statement.

Review Comment:
   I think `Parses a TRUNCATE statement` is more suitable, according to your explanation [below](https://github.com/apache/calcite/pull/3274/files#r1237971294) 



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