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Support _id aggregation operators for $group stage #3096

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merged 19 commits into from
Jul 26, 2023
Merged

Support _id aggregation operators for $group stage #3096

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Merge branch 'main' into aggregation-group-id-operators-2964
mergify[bot] Jul 26, 2023
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18 changes: 14 additions & 4 deletions integration/aggregate_documents_compat_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -618,25 +618,35 @@ func TestAggregateCompatGroup(t *testing.T) {
},
"IDType": {
pipeline: bson.A{bson.D{{"$group", bson.D{
{"_id", bson.D{{"$type", "_id"}}},
{"_id", bson.D{{"$type", "$v"}}},
{"count", bson.D{{"$count", bson.D{}}}},
}}}},
skip: "https://github.com/FerretDB/FerretDB/issues/2679",
},
"IDSum": {
pipeline: bson.A{
bson.D{{"$sort", bson.D{{"_id", 1}}}},
bson.D{{"$group", bson.D{{"_id", bson.D{{"$sum", "$v"}}}}}},
bson.D{{"$sort", bson.D{{"_id", 1}}}},
},
skip: "https://github.com/FerretDB/FerretDB/issues/2694",
},
"IDSumNonExistentField": {
pipeline: bson.A{
bson.D{{"$sort", bson.D{{"_id", 1}}}},
bson.D{{"$group", bson.D{{"_id", bson.D{{"$sum", "$non-existent"}}}}}},
bson.D{{"$sort", bson.D{{"_id", 1}}}},
},
skip: "https://github.com/FerretDB/FerretDB/issues/2694",
},
"IDSumInvalid": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"_id", bson.D{{"$sum", "$"}}}}}},
},
resultType: emptyResult,
},
"IDSumRecursiveInvalid": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"_id", bson.D{{"$sum", bson.D{{"$sum", "$"}}}}}}}},
},
resultType: emptyResult,
},
}

Expand Down
52 changes: 51 additions & 1 deletion integration/aggregate_documents_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ func TestAggregateGroupErrors(t *testing.T) {
altMessage string // optional, alternative error message for FerretDB, ignored if empty
skip string // optional, skip test with a specified reason
}{
"StageGroupUnaryOperatorSum": {
"GroupUnaryOperatorSum": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"sum", bson.D{{"$sum", bson.A{}}}}}}},
},
Expand All @@ -105,6 +105,56 @@ func TestAggregateGroupErrors(t *testing.T) {
},
altMessage: "The $sum accumulator is a unary operator",
},
"GroupTypeEmpty": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"v", bson.D{}}}}},
},
err: &mongo.CommandError{
Code: 40234,
Name: "Location40234",
Message: "The field 'v' must be an accumulator object",
},
},
"GroupTwoOperators": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"_id", bson.D{{"$type", int32(42)}, {"$op", int32(42)}}}}}},
},
err: &mongo.CommandError{
Code: 15983,
Name: "Location15983",
Message: "An object representing an expression must have exactly one field: { $type: 42, $op: 42 }",
},
},
"GroupTypeInvalidLen": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"_id", bson.D{{"$type", bson.A{"foo", "bar"}}}}}}},
},
err: &mongo.CommandError{
Code: 16020,
Name: "Location16020",
Message: "Expression $type takes exactly 1 arguments. 2 were passed in.",
},
},
"GroupNonExistentOperator": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"_id", bson.D{{"$non-existent", "foo"}}}}}},
},
err: &mongo.CommandError{
Code: 168,
Name: "InvalidPipelineOperator",
Message: "Unrecognized expression '$non-existent'",
},
},
"GroupRecursiveNonExistentOperator": {
pipeline: bson.A{
bson.D{{"$group", bson.D{{"_id", bson.D{{"$type", bson.D{{"$non-existent", "foo"}}}}}}}},
},
err: &mongo.CommandError{
Code: 168,
Name: "InvalidPipelineOperator",
Message: "Unrecognized expression '$non-existent'",
},
},
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} {
name, tc := name, tc
t.Run(name, func(t *testing.T) {
Expand Down
237 changes: 180 additions & 57 deletions internal/handlers/common/aggregations/stages/group.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,9 +18,11 @@ import (
"context"
"errors"
"fmt"
"time"

"github.com/FerretDB/FerretDB/internal/handlers/common"
"github.com/FerretDB/FerretDB/internal/handlers/common/aggregations"
"github.com/FerretDB/FerretDB/internal/handlers/common/aggregations/operators"
"github.com/FerretDB/FerretDB/internal/handlers/common/aggregations/operators/accumulators"
"github.com/FerretDB/FerretDB/internal/handlers/commonerrors"
"github.com/FerretDB/FerretDB/internal/types"
Expand Down Expand Up @@ -82,6 +84,11 @@ func newGroup(stage *types.Document) (aggregations.Stage, error) {

if field == "_id" {
if doc, ok := v.(*types.Document); ok {
if operators.IsOperator(doc) {
groupKey = v
continue
}

if err = validateExpression("$group", doc); err != nil {
return nil, err
}
Expand Down Expand Up @@ -165,73 +172,98 @@ func (g *group) Process(ctx context.Context, iter types.DocumentsIterator, close

// groupDocuments groups documents by group expression.
func (g *group) groupDocuments(ctx context.Context, in []*types.Document) ([]groupedDocuments, error) {
groupKey, ok := g.groupExpression.(string)
if !ok {
// non-string key aggregates values of all `in` documents into one aggregated document.
return []groupedDocuments{{
groupID: g.groupExpression,
documents: in,
}}, nil
}

expression, err := aggregations.NewExpression(groupKey)
if err != nil {
var exprErr *aggregations.ExpressionError
if !errors.As(err, &exprErr) {
return nil, lazyerrors.Error(err)
switch groupKey := g.groupExpression.(type) {
case *types.Document:
op, err := operators.NewOperator(groupKey)
if err != nil {
return nil, processOperatorError(err)
}

switch exprErr.Code() {
case aggregations.ErrNotExpression:
// constant value aggregates values of all `in` documents into one aggregated document.
return []groupedDocuments{{
groupID: groupKey,
documents: in,
}}, nil
case aggregations.ErrEmptyFieldPath:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
// TODO
commonerrors.ErrGroupInvalidFieldPath,
"'$' by itself is not a valid Expression",
"$group (stage)",
)
case aggregations.ErrInvalidExpression:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrFailedToParse,
fmt.Sprintf("'%s' starts with an invalid character for a user variable name", types.FormatAnyValue(groupKey)),
"$group (stage)",
)
case aggregations.ErrEmptyVariable:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrFailedToParse,
"empty variable names are not allowed",
"$group (stage)",
)
// TODO https://github.com/FerretDB/FerretDB/issues/2275
case aggregations.ErrUndefinedVariable:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrGroupUndefinedVariable,
fmt.Sprintf("Use of undefined variable: %s", types.FormatAnyValue(groupKey)),
"$group (stage)",
)
default:
panic(fmt.Sprintf("unhandled field path error %s", exprErr.Error()))
var group groupMap

for _, doc := range in {
val, err := op.Process(doc)
if err != nil {
return nil, processOperatorError(err)
}

group.addOrAppend(val, doc)
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}
}

var group groupMap
return group.docs, nil

for _, doc := range in {
val, err := expression.Evaluate(doc)
case *types.Array, float64, types.Binary, types.ObjectID, bool, time.Time, types.NullType,
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types.Regex, int32, types.Timestamp, int64:
// non-string or document key aggregates values of all `in` documents into one aggregated document.

case string:
expression, err := aggregations.NewExpression(groupKey)
if err != nil {
// $group treats non-existent fields as nulls
val = types.Null
var exprErr *aggregations.ExpressionError
if !errors.As(err, &exprErr) {
return nil, lazyerrors.Error(err)
}

switch exprErr.Code() {
case aggregations.ErrNotExpression:
// constant value aggregates values of all `in` documents into one aggregated document.
return []groupedDocuments{{
groupID: groupKey,
documents: in,
}}, nil
case aggregations.ErrEmptyFieldPath:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
// TODO
commonerrors.ErrGroupInvalidFieldPath,
"'$' by itself is not a valid Expression",
"$group (stage)",
)
case aggregations.ErrInvalidExpression:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrFailedToParse,
fmt.Sprintf("'%s' starts with an invalid character for a user variable name", types.FormatAnyValue(groupKey)),
"$group (stage)",
)
case aggregations.ErrEmptyVariable:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrFailedToParse,
"empty variable names are not allowed",
"$group (stage)",
)
// TODO https://github.com/FerretDB/FerretDB/issues/2275
case aggregations.ErrUndefinedVariable:
return nil, commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrGroupUndefinedVariable,
fmt.Sprintf("Use of undefined variable: %s", types.FormatAnyValue(groupKey)),
"$group (stage)",
)
default:
panic(fmt.Sprintf("unhandled field path error %s", exprErr.Error()))
}
}

group.addOrAppend(val, doc)
var group groupMap

for _, doc := range in {
val, err := expression.Evaluate(doc)
if err != nil {
// $group treats non-existent fields as nulls
val = types.Null
}

group.addOrAppend(val, doc)
}

return group.docs, nil

default:
panic(fmt.Sprintf("unexpected type %[1]T (%#[1]v)", groupKey))
}

return group.docs, nil
return []groupedDocuments{{
groupID: g.groupExpression,
documents: in,
}}, nil
}

// groupedDocuments contains group key and the documents for that group.
Expand Down Expand Up @@ -265,6 +297,97 @@ func (m *groupMap) addOrAppend(groupKey any, docs ...*types.Document) {
})
}

// processOperatorError takes internal error related to operator evaluation and
// returns proper CommandError that can be returned by $project aggregation stage.
//
// Command error codes:
// - ErrEmptySubProject when operator value is empty.
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// - ErrFieldPathInvalidName when FieldPath is invalid.
// - ErrNotImplemented when the operator or expression is not implemented yet.
// - ErrOperatorWrongLenOfArgs when the operator has an invalid number of arguments.
// - ErrInvalidPipelineOperator when the operator does not exist.
// - ErrFailedToParse when operator has invalid variable expression.
// - ErrGroupInvalidFieldPath when operator has empty path expression.
func processOperatorError(err error) error {
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if err == nil {
return nil
}
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var opErr operators.OperatorError
var exErr *aggregations.ExpressionError

switch {
case errors.As(err, &opErr):
switch opErr.Code() {
case operators.ErrTooManyFields:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrFieldPathInvalidName,
"Invalid $group :: caused by :: FieldPath field names may not start with '$'."+
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" Consider using $getField or $setField.",
"$group (stage)",
)
case operators.ErrNotImplemented:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrNotImplemented,
"Invalid $group :: caused by :: "+opErr.Error(),
"$group (stage)",
)
case operators.ErrArgsInvalidLen:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrOperatorWrongLenOfArgs,
"Invalid $group :: caused by :: "+opErr.Error(),
"$group (stage)",
)
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case operators.ErrInvalidExpression:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrAggregateInvalidExpression,
"Invalid $group :: caused by :: "+opErr.Error(),
"$group (stage)",
)
case operators.ErrInvalidNestedExpression:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrInvalidPipelineOperator,
"Invalid $group :: caused by :: "+opErr.Error(),
"$group (stage)",
)
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}

case errors.As(err, &exErr):
switch exErr.Code() {
case aggregations.ErrNotExpression:
// handled by upstream and this should not be reachable for existing expression implementation
fallthrough
case aggregations.ErrInvalidExpression:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrFailedToParse,
"Invalid $group :: caused by :: '$' starts with an invalid character for a user variable name",
"$group (stage)",
)
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case aggregations.ErrEmptyFieldPath:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrGroupInvalidFieldPath,
"Invalid $group :: caused by :: '$' by itself is not a valid FieldPath",
"$group (stage)",
)
case aggregations.ErrUndefinedVariable:
// TODO https://github.com/FerretDB/FerretDB/issues/2275
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrNotImplemented,
"Aggregation expression variables are not implemented yet",
"$group (stage)",
)
case aggregations.ErrEmptyVariable:
return commonerrors.NewCommandErrorMsgWithArgument(
commonerrors.ErrFailedToParse,
"Invalid $group :: caused by :: empty variable names are not allowed",
"$group (stage)",
)
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}
}

return lazyerrors.Error(err)
}

// check interfaces
var (
_ aggregations.Stage = (*group)(nil)
Expand Down