public SqlJoinInner rewrite(SqlJoinInner join) {
if (!join.getRight().isInnerJoin()) return join;
// if ( join(A, join(B, C)) ) rewrite as join(join(A,B),C)
// this then is written without brackets (and so scope changing)
// TODO abstract as organiseJoin(List<join elements>)
// and remember to do top down to find maximal join trees
SqlJoinInner right = join.getRight().asInnerJoin();
String alias1 = join.getAliasName();
String alias2 = right.getAliasName();
SqlNode sn_a = join.getLeft();
SqlNode sn_b = right.getLeft();
SqlNode sn_c = right.getRight();
SqlExprList conditions = new SqlExprList(join.getConditions());
conditions.addAll(right.getConditions());
Set<SqlTable> tables_ab = sn_a.tablesInvolved();
tables_ab.addAll(sn_b.tablesInvolved());
SqlExprList newCond_ab = new SqlExprList(); // Goes to new join(A,B)
SqlExprList newCond_c = new SqlExprList(); // Goes to new join(,C)
// Place conditions
for (SqlExpr e : conditions) {
Set<SqlColumn> cols = e.getColumnsNeeded();
// columns to tables.
Set<SqlTable> tables = tables(cols);
// Are the tables contained in tables_ab?
tables.removeAll(tables_ab);
if (tables.size() == 0) newCond_ab.add(e);
else newCond_c.add(e);
}
if (newCond_ab.size() + newCond_c.size() != conditions.size())
log.error(
String.format(
"Conditions mismatch: (%d,%d,%d)",
newCond_ab.size(), newCond_c.size(), conditions.size()));
SqlJoinInner join2 = new SqlJoinInner(sn_a, sn_b);
join2.addConditions(newCond_ab);
join2 = new SqlJoinInner(join2, sn_c);
join2.addConditions(newCond_c);
return join2;
}
