// processAliasedTable produces a builder subtree for the given AliasedTableExpr.
// If the expression is a subquery, then the the route built for it will contain
// the entire subquery tree in the from clause, as if it was a table.
// The symtab entry for the query will be a tabsym where the columns
// will be built from the select expressions of the subquery.
// Since the table aliases only contain vindex columns, we'll follow
// the same rule: only columns from the subquery that are identified as
// vindex columns will be added to the tabsym.
// A symtab symbol can only point to a route. This means that we canoot
// support complex joins in subqueries yet.
func processAliasedTable(tableExpr *sqlparser.AliasedTableExpr, vschema VSchema) (builder, error) {
switch expr := tableExpr.Expr.(type) {
case *sqlparser.TableName:
eroute, table, err := getTablePlan(expr, vschema)
if err != nil {
return nil, err
}
alias := sqlparser.TableIdent(sqlparser.String(expr))
astName := expr.Name
if tableExpr.As != "" {
alias = tableExpr.As
astName = alias
}
return newRoute(
sqlparser.TableExprs([]sqlparser.TableExpr{tableExpr}),
eroute,
table,
vschema,
alias,
astName,
), nil
case *sqlparser.Subquery:
sel, ok := expr.Select.(*sqlparser.Select)
if !ok {
return nil, errors.New("unsupported: union operator in subqueries")
}
subplan, err := processSelect(sel, vschema, nil)
if err != nil {
return nil, err
}
subroute, ok := subplan.(*route)
if !ok {
return nil, errors.New("unsupported: complex join in subqueries")
}
table := &vindexes.Table{
Keyspace: subroute.ERoute.Keyspace,
}
for _, colsyms := range subroute.Colsyms {
if colsyms.Vindex == nil {
continue
}
table.ColumnVindexes = append(table.ColumnVindexes, &vindexes.ColumnVindex{
Column: cistring.CIString(colsyms.Alias),
Vindex: colsyms.Vindex,
})
}
rtb := newRoute(
sqlparser.TableExprs([]sqlparser.TableExpr{tableExpr}),
subroute.ERoute,
table,
vschema,
tableExpr.As,
tableExpr.As,
)
subroute.Redirect = rtb
return rtb, nil
}
panic("unreachable")
}
// Find returns the route for the symbol referenced by col.
// If a reference is found, the column's Metadata is set to point
// it. Subsequent searches will reuse this meatadata.
// If autoResolve is true, and there is only one table in the symbol table,
// then an unqualified reference is assumed to be implicitly against
// that table. The table info doesn't contain the full list of columns.
// So, any column reference is presumed valid. If a Colsyms scope is
// present, then the table scope is not searched. If a symbol is found
// in the current symtab, then isLocal is set to true. Otherwise, the
// search is continued in the outer symtab. If so, isLocal will be set
// to false. If the symbol was not found, an error is returned.
// isLocal must be checked before you can push-down (or pull-out)
// a construct.
// If a symbol was found in an outer scope, then the column reference
// is added to the Externs field.
func (st *symtab) Find(col *sqlparser.ColName, autoResolve bool) (rb *route, isLocal bool, err error) {
if m, ok := col.Metadata.(sym); ok {
return m.Route(), m.Symtab() == st, nil
}
if len(st.Colsyms) != 0 {
name := sqlparser.String(col)
starname := sqlparser.String(&sqlparser.ColName{
Name: sqlparser.NewColIdent("*"),
Qualifier: col.Qualifier,
})
for _, colsym := range st.Colsyms {
if colsym.Alias.EqualString(name) || colsym.Alias.EqualString(starname) || colsym.Alias.EqualString("*") {
col.Metadata = colsym
return colsym.Route(), true, nil
}
}
if st.Outer != nil {
// autoResolve only allowed for innermost scope.
rb, _, err = st.Outer.Find(col, false)
if err == nil {
st.Externs = append(st.Externs, col)
}
return rb, false, err
}
return nil, false, fmt.Errorf("symbol %s not found", sqlparser.String(col))
}
qualifier := sqlparser.TableIdent(sqlparser.String(col.Qualifier))
if qualifier == "" && autoResolve && len(st.tables) == 1 {
for _, t := range st.tables {
qualifier = t.Alias
break
}
}
alias := st.findTable(qualifier)
if alias == nil {
if st.Outer != nil {
// autoResolve only allowed for innermost scope.
rb, _, err = st.Outer.Find(col, false)
if err == nil {
st.Externs = append(st.Externs, col)
}
return rb, false, err
}
return nil, false, fmt.Errorf("symbol %s not found", sqlparser.String(col))
}
col.Metadata = alias
return alias.Route(), true, nil
}