// newExplainPlanNode instantiates a planNode that runs an EXPLAIN query.
func (p *planner) makeExplainPlanNode(explainer explainer, expanded bool, plan planNode) planNode {
columns := ResultColumns{
// Level is the depth of the node in the tree.
{Name: "Level", Typ: parser.TypeInt},
// Type is the node type.
{Name: "Type", Typ: parser.TypeString},
// Field is the part of the node that a row of output pertains to.
// For example a select node may have separate "render" and
// "filter" fields.
{Name: "Field", Typ: parser.TypeString},
// Description contains details about the field.
{Name: "Description", Typ: parser.TypeString},
}
if explainer.showMetadata {
// Columns is the type signature of the data source.
columns = append(columns, ResultColumn{Name: "Columns", Typ: parser.TypeString})
// Ordering indicates the known ordering of the data from this source.
columns = append(columns, ResultColumn{Name: "Ordering", Typ: parser.TypeString})
}
explainer.fmtFlags = parser.FmtExpr(
explainer.showTypes, explainer.symbolicVars, explainer.qualifyNames)
node := &explainPlanNode{
explainer: explainer,
expanded: expanded,
plan: plan,
results: p.newContainerValuesNode(columns, 0),
}
return node
}
// planToString uses explain() to build a string representation of the planNode.
func planToString(plan planNode) string {
var buf bytes.Buffer
e := explainer{
showMetadata: true,
showTypes: true,
showExprs: true,
showSelectTop: true,
fmtFlags: parser.FmtExpr(parser.FmtSimple, true, true, true),
makeRow: func(level int, name, field, description string, plan planNode) {
if field != "" {
field = "." + field
}
if plan == nil {
fmt.Fprintf(&buf, "%d %s%s %s\n", level, name, field, description)
} else {
fmt.Fprintf(&buf, "%d %s%s %s %s %s\n", level, name, field, description,
formatColumns(plan.Columns(), true),
plan.Ordering().AsString(plan.Columns()),
)
}
},
}
_ = walkPlan(plan, &e)
return buf.String()
}