[CALCITE-7810] Write Rex string literal digests directly

core/src/main/java/org/apache/calcite/rex/RexLiteral.java

@@ -663,7 +663,7 @@ private static void appendAsJava(@Nullable Comparable value, StringBuilder sb,
             (nlsString.getCharsetName() != null)
                 && !nlsString.getCharsetName().equals(
                 CalciteSystemProperty.DEFAULT_CHARSET.value());
-        sb.append(nlsString.asSql(includeCharset, false));
+        nlsString.asSql(sb, includeCharset, false);
       }
       break;
     case BOOLEAN:

core/src/main/java/org/apache/calcite/util/NlsString.java

@@ -315,6 +315,12 @@ public String asSql(boolean prefix, boolean suffix) {
     return asSql(prefix, suffix, AnsiSqlDialect.DEFAULT);
   }
 
+  /** As {@link #asSql(StringBuilder, boolean, boolean, SqlDialect)} but with
+   * SQL standard dialect. */
+  public void asSql(StringBuilder buf, boolean prefix, boolean suffix) {
+    asSql(buf, prefix, suffix, AnsiSqlDialect.DEFAULT);
+  }
+
   /**
    * Returns the string quoted for SQL, for example <code>_ISO-8859-1'is it a
    * plane? no it''s superman!'</code>.
@@ -329,16 +335,32 @@ public String asSql(
       boolean suffix,
       SqlDialect dialect) {
     StringBuilder ret = new StringBuilder();
-    dialect.quoteStringLiteral(ret, prefix ? charsetName : null, getValue());
+    asSql(ret, prefix, suffix, dialect);
+    return ret.toString();
+  }
+
+  /**
+   * Appends this string quoted for SQL.
+   *
+   * @param buf Buffer to append to
+   * @param prefix if true, prefix the character set name
+   * @param suffix if true, suffix the collation clause
+   * @param dialect Dialect
+   */
+  public void asSql(
+      StringBuilder buf,
+      boolean prefix,
+      boolean suffix,
+      SqlDialect dialect) {
+    dialect.quoteStringLiteral(buf, prefix ? charsetName : null, getValue());
 
     // NOTE jvs 3-Feb-2005:  see FRG-78 for why this should go away
     if (false) {
       if (suffix && (null != collation)) {
-        ret.append(" ");
-        ret.append(collation.toString());
+        buf.append(" ");
+        buf.append(collation.toString());
       }
     }
-    return ret.toString();
   }
 
   /**

core/src/test/java/org/apache/calcite/util/UtilTest.java

@@ -3002,6 +3002,13 @@ private void checkNameMultimap(String s, NameMultimap<Integer> map) {
     assertThat(s2, hasToString(s.toString()));
   }
 
+  @Test void testNlsStringAsSqlStringBuilder() {
+    final NlsString s = new NlsString("isn't", "LATIN1", SqlCollation.IMPLICIT);
+    final StringBuilder buf = new StringBuilder("literal: ");
+    s.asSql(buf, true, false);
+    assertThat(buf, hasToString("literal: _LATIN1'isn''t'"));
+  }
+
   /** Tests that {@link NlsString#compareTo} is consistent with
    * {@link NlsString#equals}: {@code x.compareTo(y) == 0} iff
    * {@code x.equals(y)} for values that differ in charset or collation. */