sq/libsq/query_model.go

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package libsq
import (
"fmt"
"github.com/neilotoole/sq/libsq/core/loz"
"github.com/neilotoole/sq/libsq/ast"
"github.com/neilotoole/sq/libsq/core/errz"
"golang.org/x/exp/slog"
)
// queryModel is a model of an SLQ query built from the AST.
type queryModel struct {
AST *ast.AST
Table ast.Tabler
Cols []ast.ResultColumn
Range *ast.RowRangeNode
Where *ast.WhereNode
OrderBy *ast.OrderByNode
GroupBy *ast.GroupByNode
Distinct *ast.UniqueNode
}
func (qm *queryModel) String() string {
return fmt.Sprintf("%v | %v | %v", qm.Table, qm.Cols, qm.Range)
}
// buildQueryModel creates a queryModel instance from the AST.
func buildQueryModel(log *slog.Logger, a *ast.AST) (*queryModel, error) {
if len(a.Segments()) == 0 {
return nil, errz.Errorf("query model error: query does not have enough segments")
}
insp := ast.NewInspector(a)
var tabler ast.Tabler
var ok bool
tablerSeg, err := insp.FindFinalTablerSegment()
if err != nil {
log.Debug("No Tabler segment.")
}
if tablerSeg != nil {
if len(tablerSeg.Children()) != 1 {
return nil, errz.Errorf(
"the final selectable segment must have exactly one selectable element, but found %d elements",
len(tablerSeg.Children()))
}
if tabler, ok = tablerSeg.Children()[0].(ast.Tabler); !ok {
return nil, errz.Errorf(
"the final selectable segment must have exactly one selectable element, but found element %T(%s)",
tablerSeg.Children()[0], tablerSeg.Children()[0].Text())
}
}
qm := &queryModel{AST: a, Table: tabler}
if qm.Range, err = insp.FindRowRangeNode(); err != nil {
return nil, err
}
seg, err := insp.FindColExprSegment()
if err != nil {
return nil, err
}
if seg != nil {
var colExprs []ast.ResultColumn
if colExprs, ok = loz.ToSliceType[ast.Node, ast.ResultColumn](seg.Children()...); !ok {
return nil, errz.Errorf("segment children contained elements that were not of type %T: %s",
ast.ResultColumn(nil), seg.Text())
}
qm.Cols = colExprs
}
whereClauses, err := insp.FindWhereClauses()
if err != nil {
return nil, err
}
if len(whereClauses) > 1 {
return nil, errz.Errorf("only one WHERE clause is supported, but found %d", len(whereClauses))
} else if len(whereClauses) == 1 {
qm.Where = whereClauses[0]
}
if qm.OrderBy, err = insp.FindOrderByNode(); err != nil {
return nil, err
}
if qm.GroupBy, err = insp.FindGroupByNode(); err != nil {
return nil, err
}
if qm.Distinct, err = insp.FindUniqueNode(); err != nil {
return nil, err
}
return qm, nil
}