/**
* Returns whether a node represents the NULL value.
*
* <p>Examples:
*
* <ul>
* <li>For {@link org.eigenbase.rex.RexLiteral} Unknown, returns false.
* <li>For <code>CAST(NULL AS <i>type</i>)</code>, returns true if <code>
* allowCast</code> is true, false otherwise.
* <li>For <code>CAST(CAST(NULL AS <i>type</i>) AS <i>type</i>))</code>, returns false.
* </ul>
*/
public static boolean isNullLiteral(RexNode node, boolean allowCast) {
if (node instanceof RexLiteral) {
RexLiteral literal = (RexLiteral) node;
if (literal.getTypeName() == SqlTypeName.NULL) {
assert (null == literal.getValue());
return true;
} else {
// We don't regard UNKNOWN -- SqlLiteral(null,Boolean) -- as
// NULL.
return false;
}
}
if (allowCast) {
if (node.isA(RexKind.Cast)) {
RexCall call = (RexCall) node;
if (isNullLiteral(call.operands[0], false)) {
// node is "CAST(NULL as type)"
return true;
}
}
}
return false;
}
/** Converts an expression from {@link RexNode} to {@link SqlNode} format. */
SqlNode toSql(RexProgram program, RexNode rex) {
if (rex instanceof RexLocalRef) {
final int index = ((RexLocalRef) rex).getIndex();
return toSql(program, program.getExprList().get(index));
} else if (rex instanceof RexInputRef) {
return field(((RexInputRef) rex).getIndex());
} else if (rex instanceof RexLiteral) {
final RexLiteral literal = (RexLiteral) rex;
switch (literal.getTypeName().getFamily()) {
case CHARACTER:
return SqlLiteral.createCharString((String) literal.getValue2(), POS);
case NUMERIC:
case EXACT_NUMERIC:
return SqlLiteral.createExactNumeric(literal.getValue().toString(), POS);
case APPROXIMATE_NUMERIC:
return SqlLiteral.createApproxNumeric(literal.getValue().toString(), POS);
case BOOLEAN:
return SqlLiteral.createBoolean((Boolean) literal.getValue(), POS);
case DATE:
return SqlLiteral.createDate((Calendar) literal.getValue(), POS);
case TIME:
return SqlLiteral.createTime(
(Calendar) literal.getValue(), literal.getType().getPrecision(), POS);
case TIMESTAMP:
return SqlLiteral.createTimestamp(
(Calendar) literal.getValue(), literal.getType().getPrecision(), POS);
case ANY:
switch (literal.getTypeName()) {
case NULL:
return SqlLiteral.createNull(POS);
// fall through
}
default:
throw new AssertionError(literal + ": " + literal.getTypeName());
}
} else if (rex instanceof RexCall) {
final RexCall call = (RexCall) rex;
final SqlOperator op = call.getOperator();
final List<SqlNode> nodeList = toSql(program, call.getOperands());
if (op == SqlStdOperatorTable.CAST) {
RelDataType type = call.getType();
if (type.getSqlTypeName() == SqlTypeName.VARCHAR
&& dialect.getDatabaseProduct() == SqlDialect.DatabaseProduct.MYSQL) {
// MySQL doesn't have a VARCHAR type, only CHAR.
nodeList.add(
new SqlDataTypeSpec(
new SqlIdentifier("CHAR", POS), type.getPrecision(), -1, null, null, POS));
} else {
nodeList.add(toSql(type));
}
}
if (op == SqlStdOperatorTable.CASE) {
final SqlNode valueNode;
final List<SqlNode> whenList = Expressions.list();
final List<SqlNode> thenList = Expressions.list();
final SqlNode elseNode;
if (nodeList.size() % 2 == 0) {
// switched:
// "case x when v1 then t1 when v2 then t2 ... else e end"
valueNode = nodeList.get(0);
for (int i = 1; i < nodeList.size() - 1; i += 2) {
whenList.add(nodeList.get(i));
thenList.add(nodeList.get(i + 1));
}
} else {
// other: "case when w1 then t1 when w2 then t2 ... else e end"
valueNode = null;
for (int i = 0; i < nodeList.size() - 1; i += 2) {
whenList.add(nodeList.get(i));
thenList.add(nodeList.get(i + 1));
}
}
elseNode = nodeList.get(nodeList.size() - 1);
return op.createCall(
POS,
valueNode,
new SqlNodeList(whenList, POS),
new SqlNodeList(thenList, POS),
elseNode);
}
if (op instanceof SqlBinaryOperator && nodeList.size() > 2) {
// In RexNode trees, OR and AND have any number of children;
// SqlCall requires exactly 2. So, convert to a left-deep binary tree.
return createLeftCall(op, nodeList);
}
return op.createCall(new SqlNodeList(nodeList, POS));
} else {
throw new AssertionError(rex);
}
}
