// The distsql Expression uses the placeholder syntax (@1, @2, @3..) to
// refer to columns. We format the expression using an IndexedVar formatting
// interceptor. A columnMap can optionally be used to remap the indices.
func distSQLExpression(expr parser.TypedExpr, columnMap []int) distsql.Expression {
if expr == nil {
return distsql.Expression{}
}
var f parser.FmtFlags
if columnMap == nil {
f = parser.FmtIndexedVarFormat(
func(buf *bytes.Buffer, _ parser.FmtFlags, _ parser.IndexedVarContainer, idx int) {
fmt.Fprintf(buf, "@%d", idx+1)
},
)
} else {
f = parser.FmtIndexedVarFormat(
func(buf *bytes.Buffer, _ parser.FmtFlags, _ parser.IndexedVarContainer, idx int) {
remappedIdx := columnMap[idx]
if remappedIdx < 0 {
panic(fmt.Sprintf("unmapped index %d", idx))
}
fmt.Fprintf(buf, "@%d", remappedIdx+1)
},
)
}
var buf bytes.Buffer
expr.Format(&buf, f)
return distsql.Expression{Expr: buf.String()}
}
// The distsqlrun Expression uses the placeholder syntax (@1, @2, @3..) to
// refer to columns. We format the expression using the IndexedVar and StarDatum
// formatting interceptors. A columnMap can optionally be used to remap the
// indices.
func distSQLExpression(expr parser.TypedExpr, columnMap []int) distsqlrun.Expression {
if expr == nil {
return distsqlrun.Expression{}
}
// TODO(irfansharif): currently there’s no nice way to “compose” FmtFlags
// out of multiple FmtFlag‘s (this unit does not exist today).
// By introducing such composability, the flags below can be constructed
// once and reused for subsequent calls. Additionally the construction of
// the flags would not need to inspect expression type.
var f parser.FmtFlags
switch expr.(type) {
case *parser.StarDatum:
// By default parser.StarDatum is rendered as a DInt(0), but formatting
// this as 0 we can replicate this behavior in distsqlrun.
f = parser.FmtStarDatumFormat(
func(buf *bytes.Buffer, _ parser.FmtFlags) {
fmt.Fprintf(buf, "0")
},
)
default:
if columnMap == nil {
f = parser.FmtIndexedVarFormat(
func(buf *bytes.Buffer, _ parser.FmtFlags, _ parser.IndexedVarContainer, idx int) {
fmt.Fprintf(buf, "@%d", idx+1)
},
)
} else {
f = parser.FmtIndexedVarFormat(
func(buf *bytes.Buffer, _ parser.FmtFlags, _ parser.IndexedVarContainer, idx int) {
remappedIdx := columnMap[idx]
if remappedIdx < 0 {
panic(fmt.Sprintf("unmapped index %d", idx))
}
fmt.Fprintf(buf, "@%d", remappedIdx+1)
},
)
}
}
var buf bytes.Buffer
expr.Format(&buf, f)
return distsqlrun.Expression{Expr: buf.String()}
}