vlsi commented on a change in pull request #2271:
URL: https://github.com/apache/calcite/pull/2271#discussion_r535559413
##########
File path:
core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java
##########
@@ -1506,6 +1508,83 @@ private SqlNode getCastedSqlNode(SqlNode argInput,
RelDataType varType,
}
}
+ /** Convertlet that handles Oracle's {@code SUBSTR} function. */
+ private static class OracleSubstrConvertlet implements SqlRexConvertlet {
+ @Override public RexNode convertCall(SqlRexContext cx, SqlCall call) {
+ // Translate
+ // SUBSTR(value, start, length)
+ // to
+ // CASE
+ // WHEN length < 0 THEN ""
+ // WHEN start + length(value) < 0 THEN ""
+ // WHEN start = 0 THEN substring(value, 1, length)
+ // WHEN start < 0 THEN substring(value, start + length(value) + 1,
length)
+ // ELSE substring(value, start, length)
+ // END
+ //
+ // Translate
+ // SUBSTR(value, start)
+ // to
+ // CASE
+ // WHEN start + length(value) < 0 THEN ""
+ // WHEN start = 0 THEN substring(value, 1)
+ // WHEN start < 0 THEN substring(value, start + length(value) + 1)
+ // ELSE substring(value, start)
+ // END
+
+ final RexBuilder rexBuilder = cx.getRexBuilder();
+ final List<RexNode> exprs =
+ convertOperands(cx, call, SqlOperandTypeChecker.Consistency.NONE);
+ final RexNode value = exprs.get(0);
+ final RexNode start = exprs.get(1);
+ final RexNode zeroLiteral = rexBuilder.makeLiteral(0, start.getType(),
false);
+ final RexNode oneLiteral = rexBuilder.makeLiteral(1, start.getType(),
false);
+ final RexNode emptyStrLiteral = rexBuilder.makeLiteral("",
value.getType(), false);
+
+ final RexNode valueLength =
+ rexBuilder.makeCall(SqlStdOperatorTable.CHAR_LENGTH, value);
+ final RexNode negativeIndexStart =
rexBuilder.makeCall(SqlStdOperatorTable.PLUS,
+ rexBuilder.makeCall(SqlStdOperatorTable.PLUS, valueLength, start),
+ oneLiteral);
+
+ final RexNode startIndexOutOfBound =
rexBuilder.makeCall(SqlStdOperatorTable.LESS_THAN,
+ rexBuilder.makeCall(SqlStdOperatorTable.PLUS, start, valueLength),
+ zeroLiteral);
+ final RexNode startLessThanZero =
+ rexBuilder.makeCall(SqlStdOperatorTable.LESS_THAN, start,
zeroLiteral);
+ final RexNode startIsZero =
+ rexBuilder.makeCall(SqlStdOperatorTable.EQUALS, start, zeroLiteral);
+
+ final Function<RexNode, RexNode> startToSubstr;
+ switch (call.operandCount()) {
+ case 2:
+ startToSubstr = startRex ->
+ rexBuilder.makeCall(SqlStdOperatorTable.SUBSTRING, value,
startRex);
+ return rexBuilder.makeCall(SqlStdOperatorTable.CASE,
+ startIndexOutOfBound, emptyStrLiteral,
+ startIsZero, startToSubstr.apply(oneLiteral),
+ startLessThanZero, startToSubstr.apply(negativeIndexStart),
+ startToSubstr.apply(start));
+ case 3:
+ final RexNode length = exprs.get(2);
+ final RexNode lengthLessThanZero =
+ rexBuilder.makeCall(SqlStdOperatorTable.LESS_THAN, length,
zeroLiteral);
+
+ startToSubstr = startRex ->
+ rexBuilder.makeCall(SqlStdOperatorTable.SUBSTRING, value,
startRex, length);
+
+ return rexBuilder.makeCall(SqlStdOperatorTable.CASE,
+ lengthLessThanZero, emptyStrLiteral,
+ startIndexOutOfBound, emptyStrLiteral,
+ startIsZero, startToSubstr.apply(oneLiteral),
+ startLessThanZero, startToSubstr.apply(negativeIndexStart),
+ startToSubstr.apply(start));
+ default:
+ throw new AssertionError();
Review comment:
Please add the relevant message to clarify why this branch must not be
reachable.
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