@Override
public void meet(Count node) throws RuntimeException {
builder.append("COUNT(");
if (node.isDistinct()) {
builder.append("DISTINCT ");
}
if (node.getArg() == null) {
// this is a weird special case where we need to expand to all variables selected in the query
// wrapped
// by the group; we cannot simply use "*" because the concept of variables is a different one
// in SQL,
// so instead we construct an ARRAY of the bindings of all variables
List<String> countVariables = new ArrayList<>();
for (SQLVariable v : parent.getVariables().values()) {
if (v.getProjectionType() == ValueType.NONE) {
Preconditions.checkState(
v.getExpressions().size() > 0, "no expressions available for variable");
countVariables.add(v.getExpressions().get(0));
}
}
builder.append("ARRAY[");
Joiner.on(',').appendTo(builder, countVariables);
builder.append("]");
} else {
optypes.push(ValueType.NODE);
node.getArg().visit(this);
optypes.pop();
}
builder.append(")");
}
@Override
public void meet(Exists node) throws RuntimeException {
// TODO: need to make sure that variables of the parent are visible in the subquery
// - pattern names need to be unique even in subqueries
// - variable lookup for expressions in the subquery need to refer to the parent
SQLBuilder sq_builder =
new SQLBuilder(
node.getSubQuery(),
parent.getBindings(),
parent.getDataset(),
parent.getConverter(),
parent.getDialect(),
"_",
Collections.EMPTY_SET,
copyVariables(parent.getVariables()));
builder.append("EXISTS (").append(sq_builder.build()).append(")");
}
private String getVariableAlias(String varName) {
return parent.getVariables().get(varName).getAlias();
}
private String getVariableAlias(Var var) {
return parent.getVariables().get(var.getName()).getAlias();
}
@Override
public void meet(Var node) throws RuntimeException {
// distinguish between the case where the variable is plain and the variable is bound
SQLVariable sv = parent.getVariables().get(node.getName());
if (sv == null) {
builder.append("NULL");
} else if (sv.getBindings().size() > 0) {
// in case the variable is actually an alias for an expression, we evaluate that expression
// instead, effectively replacing the
// variable occurrence with its value
sv.getBindings().get(0).visit(this);
} else {
String var = sv.getAlias();
if (sv.getProjectionType() != ValueType.NODE && sv.getProjectionType() != ValueType.NONE) {
// in case the variable represents a constructed or bound value instead of a node, we need
// to
// use the SQL expression as value; SQL should take care of proper casting...
// TODO: explicit casting needed?
builder.append(sv.getExpressions().get(0));
} else {
// in case the variable represents an entry from the NODES table (i.e. has been bound to a
// node
// in the database, we take the NODES alias and resolve to the correct column according to
// the
// operator type
switch (optypes.peek()) {
case STRING:
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(var).append(".svalue");
break;
case INT:
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(var).append(".ivalue");
break;
case DECIMAL:
case DOUBLE:
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(var).append(".dvalue");
break;
case BOOL:
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(var).append(".bvalue");
break;
case DATE:
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(var).append(".tvalue");
break;
case TZDATE:
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(parent.getDialect().getDateTimeTZ(var));
break;
case URI:
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(var).append(".svalue");
break;
case TERM:
case NODE:
if (sv.getExpressions().size() > 0) {
// this allows us to avoid joins with the nodes table for simple expressions that only
// need the ID
builder.append(sv.getExpressions().get(0));
} else {
Preconditions.checkState(var != null, "no alias available for variable");
builder.append(var).append(".id");
}
break;
}
}
}
}