From c0fdb8e69aea95a62fa1fd4eb4f92b01a135a361 Mon Sep 17 00:00:00 2001
From: Lorant Polya <lorant.polya@sap.com>
Date: Mon, 29 May 2023 15:54:54 -0700
Subject: [PATCH 1/6] Hana Insert Impl Basics

---
 internal/handlers/hana/hanadb/collections.go |  27 +++-
 internal/handlers/hana/hanadb/databases.go   |  29 ++++-
 internal/handlers/hana/hanadb/insert.go      |  57 +++++++++
 internal/handlers/hana/hanadb/query.go       |  21 ++++
 internal/handlers/hana/msg_create.go         |   9 +-
 internal/handlers/hana/msg_drop.go           |   7 +-
 internal/handlers/hana/msg_dropdatabase.go   |   6 +-
 internal/handlers/hana/msg_insert.go         | 124 ++++++++++++++++++-
 8 files changed, 263 insertions(+), 17 deletions(-)
 create mode 100644 internal/handlers/hana/hanadb/insert.go
 create mode 100644 internal/handlers/hana/hanadb/query.go

diff --git a/internal/handlers/hana/hanadb/collections.go b/internal/handlers/hana/hanadb/collections.go
index c2ca1dc6ddb9..158b60d30521 100644
--- a/internal/handlers/hana/hanadb/collections.go
+++ b/internal/handlers/hana/hanadb/collections.go
@@ -16,25 +16,40 @@ package hanadb
 
 import (
 	"context"
+	"errors"
 	"fmt"
 )
 
 // CreateCollection creates a new SAP HANA JSON Document Store collection.
 //
 // It returns ErrAlreadyExist if collection already exist.
-func (hanaPool *Pool) CreateCollection(ctx context.Context, db, collection string) error {
-	sql := fmt.Sprintf("CREATE COLLECTION %q.%q", db, collection)
+func (hanaPool *Pool) CreateCollection(ctx context.Context, qp *QueryParams) error {
+	sql := fmt.Sprintf("CREATE COLLECTION %q.%q", qp.DB, qp.Collection)
 
 	_, err := hanaPool.ExecContext(ctx, sql)
 
 	return getHanaErrorIfExists(err)
 }
 
-// DropCollection drops collection
+// CreateCollectionIfNotExists creates a new SAP HANA JSON Document Store collection.
 //
-// It returns ErrTableNotExist is collection does not exist.
-func (hanaPool *Pool) DropCollection(ctx context.Context, db, collection string) error {
-	sql := fmt.Sprintf("DROP COLLECTION %q.%q", db, collection)
+// Returns nil if collection already exist.
+func (hanaPool *Pool) CreateCollectionIfNotExists(ctx context.Context, qp *QueryParams) error {
+	err := hanaPool.CreateCollection(ctx, qp)
+
+	switch {
+	case errors.Is(err, ErrCollectionAlreadyExist):
+		return nil
+	default:
+		return err
+	}
+}
+
+// DropCollection drops collection.
+//
+// Returns ErrTableNotExist is collection does not exist.
+func (hanaPool *Pool) DropCollection(ctx context.Context, qp *QueryParams) error {
+	sql := fmt.Sprintf("DROP COLLECTION %q.%q", qp.DB, qp.Collection)
 
 	_, err := hanaPool.ExecContext(ctx, sql)
 
diff --git a/internal/handlers/hana/hanadb/databases.go b/internal/handlers/hana/hanadb/databases.go
index 5ac55dd53e4e..614191a2be84 100644
--- a/internal/handlers/hana/hanadb/databases.go
+++ b/internal/handlers/hana/hanadb/databases.go
@@ -16,23 +16,40 @@ package hanadb
 
 import (
 	"context"
+	"errors"
 	"fmt"
 )
 
 // CreateSchema creates a schema in SAP HANA JSON Document Store.
-func (hanaPool *Pool) CreateSchema(ctx context.Context, db string) error {
-	sqlStmt := fmt.Sprintf("CREATE SCHEMA %q", db)
+//
+//	Returns ErrSchemaAlreadyExist if schema already exists.
+func (hanaPool *Pool) CreateSchema(ctx context.Context, qp *QueryParams) error {
+	sqlStmt := fmt.Sprintf("CREATE SCHEMA %q", qp.DB)
 
 	_, err := hanaPool.ExecContext(ctx, sqlStmt)
 
 	return getHanaErrorIfExists(err)
 }
 
-// DropSchema drops database
+// CreateSchemaIfNotExists creates a schema in SAP HANA JSON Document Store.
+//
+// Returns nil if the schema already exists.
+func (hanaPool *Pool) CreateSchemaIfNotExists(ctx context.Context, qp *QueryParams) error {
+	err := hanaPool.CreateSchema(ctx, qp)
+
+	switch {
+	case errors.Is(err, ErrSchemaAlreadyExist):
+		return nil
+	default:
+		return err
+	}
+}
+
+// DropSchema drops database.
 //
-// It returns ErrSchemaNotExist if schema does not exist.
-func (hanaPool *Pool) DropSchema(ctx context.Context, db string) error {
-	sql := fmt.Sprintf("DROP SCHEMA %q CASCADE", db)
+// Returns ErrSchemaNotExist if schema does not exist.
+func (hanaPool *Pool) DropSchema(ctx context.Context, qp *QueryParams) error {
+	sql := fmt.Sprintf("DROP SCHEMA %q CASCADE", qp.DB)
 
 	_, err := hanaPool.ExecContext(ctx, sql)
 
diff --git a/internal/handlers/hana/hanadb/insert.go b/internal/handlers/hana/hanadb/insert.go
new file mode 100644
index 000000000000..49b2dfc790dd
--- /dev/null
+++ b/internal/handlers/hana/hanadb/insert.go
@@ -0,0 +1,57 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hanadb
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/FerretDB/FerretDB/internal/handlers/sjson"
+	"github.com/FerretDB/FerretDB/internal/types"
+	"github.com/FerretDB/FerretDB/internal/util/must"
+)
+
+// CreateSchema inserts a document into a collection in SAP HANA JSON Document Store.
+func (hanaPool *Pool) InsertOne(ctx context.Context, qp *QueryParams, doc *types.Document) error {
+	err := hanaPool.CreateSchemaIfNotExists(ctx, qp)
+
+	switch {
+	case err == nil:
+		// Success case
+	default:
+		return err
+	}
+
+	err = hanaPool.CreateCollectionIfNotExists(ctx, qp)
+
+	switch {
+	case err == nil:
+		// Success case
+	default:
+		return err
+	}
+
+	return hanaPool.Insert(ctx, qp, doc)
+}
+
+// CreateSchema inserts a document into a collection in SAP HANA JSON Document Store.
+func (hanaPool *Pool) Insert(ctx context.Context, qp *QueryParams, doc *types.Document) error {
+	sqlStmt := fmt.Sprintf("insert into %q.%q values($1)", qp.DB, qp.Collection)
+
+	// sjson.MarshalSingleValue can be used because the Hana insert json format is just a json string
+	_, err := hanaPool.ExecContext(ctx, sqlStmt, must.NotFail(sjson.MarshalSingleValue(doc)))
+
+	return getHanaErrorIfExists(err)
+}
diff --git a/internal/handlers/hana/hanadb/query.go b/internal/handlers/hana/hanadb/query.go
new file mode 100644
index 000000000000..ea968fa59449
--- /dev/null
+++ b/internal/handlers/hana/hanadb/query.go
@@ -0,0 +1,21 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hanadb
+
+// QueryParams represents options/parameters used for SQL query/statement.
+type QueryParams struct {
+	DB         string
+	Collection string
+}
diff --git a/internal/handlers/hana/msg_create.go b/internal/handlers/hana/msg_create.go
index 7af30795871a..90b44378a239 100644
--- a/internal/handlers/hana/msg_create.go
+++ b/internal/handlers/hana/msg_create.go
@@ -87,7 +87,12 @@ func (h *Handler) MsgCreate(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg,
 		return nil, err
 	}
 
-	err = dbPool.CreateSchema(ctx, db)
+	qp := hanadb.QueryParams{
+		DB:         db,
+		Collection: collection,
+	}
+
+	err = dbPool.CreateSchema(ctx, &qp)
 
 	switch {
 	case err == nil:
@@ -101,7 +106,7 @@ func (h *Handler) MsgCreate(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg,
 		return nil, lazyerrors.Error(err)
 	}
 
-	err = dbPool.CreateCollection(ctx, db, collection)
+	err = dbPool.CreateCollection(ctx, &qp)
 
 	switch {
 	case err == nil:
diff --git a/internal/handlers/hana/msg_drop.go b/internal/handlers/hana/msg_drop.go
index 1922d9a0300f..98e20115afe2 100644
--- a/internal/handlers/hana/msg_drop.go
+++ b/internal/handlers/hana/msg_drop.go
@@ -53,7 +53,12 @@ func (h *Handler) MsgDrop(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg, er
 		return nil, err
 	}
 
-	err = dbPool.DropCollection(ctx, db, collection)
+	qp := hanadb.QueryParams{
+		DB:         db,
+		Collection: collection,
+	}
+
+	err = dbPool.DropCollection(ctx, &qp)
 
 	switch {
 	case err == nil:
diff --git a/internal/handlers/hana/msg_dropdatabase.go b/internal/handlers/hana/msg_dropdatabase.go
index 3bf43bcd628a..10afb7a86242 100644
--- a/internal/handlers/hana/msg_dropdatabase.go
+++ b/internal/handlers/hana/msg_dropdatabase.go
@@ -45,9 +45,13 @@ func (h *Handler) MsgDropDatabase(ctx context.Context, msg *wire.OpMsg) (*wire.O
 		return nil, err
 	}
 
+	qp := hanadb.QueryParams{
+		DB: db,
+	}
+
 	res := must.NotFail(types.NewDocument())
 
-	err = dbPool.DropSchema(ctx, db)
+	err = dbPool.DropSchema(ctx, &qp)
 
 	switch {
 	case err == nil:
diff --git a/internal/handlers/hana/msg_insert.go b/internal/handlers/hana/msg_insert.go
index 6c59d8b77e27..4a610fe1f792 100644
--- a/internal/handlers/hana/msg_insert.go
+++ b/internal/handlers/hana/msg_insert.go
@@ -16,12 +16,134 @@ package hana
 
 import (
 	"context"
+	"errors"
+	"fmt"
 
+	"github.com/FerretDB/FerretDB/internal/handlers/common"
+	"github.com/FerretDB/FerretDB/internal/handlers/commonerrors"
+	"github.com/FerretDB/FerretDB/internal/handlers/hana/hanadb"
+	"github.com/FerretDB/FerretDB/internal/types"
+	"github.com/FerretDB/FerretDB/internal/util/lazyerrors"
 	"github.com/FerretDB/FerretDB/internal/util/must"
 	"github.com/FerretDB/FerretDB/internal/wire"
 )
 
 // MsgInsert implements HandlerInterface.
 func (h *Handler) MsgInsert(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg, error) {
-	return nil, notImplemented(must.NotFail(msg.Document()).Command())
+	dbPool, err := h.DBPool(ctx)
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	document, err := msg.Document()
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	ignoredFields := []string{
+		"writeConcern",
+	}
+	common.Ignored(document, h.L, ignoredFields...)
+
+	params, err := common.GetInsertParams(document, h.L)
+	if err != nil {
+		return nil, err
+	}
+
+	qp := hanadb.QueryParams{
+		DB:         params.DB,
+		Collection: params.Collection,
+	}
+
+	inserted, insErrors := insertMany(ctx, dbPool, &qp, params.Docs, params.Ordered)
+
+	replyDoc := must.NotFail(types.NewDocument(
+		"n", inserted,
+		"ok", float64(1),
+	))
+
+	if insErrors.Len() > 0 {
+		replyDoc = insErrors.Document()
+	}
+
+	var reply wire.OpMsg
+	must.NoError(reply.SetSections(wire.OpMsgSection{
+		Documents: []*types.Document{replyDoc},
+	}))
+
+	return &reply, nil
+}
+
+func insertMany(ctx context.Context, dbPool *hanadb.Pool, qp *hanadb.QueryParams, docs *types.Array, ordered bool) (int32, *commonerrors.WriteErrors) { //nolint:lll // argument list is too long
+	var inserted int32
+	var insErrors commonerrors.WriteErrors
+
+	// TODO: Bulk Insert
+	// Attempt to insert all the documents in the same request to make insert faster.
+	/*if err := dbPool.InsertManyDocuments(ctx, qp docs); err == nil {
+		return int32(docs.Len()), &insErrors
+	}*/
+
+	// If the transaction failed, attempt to insert each document separately.
+	for i := 0; i < docs.Len(); i++ {
+		doc := must.NotFail(docs.Get(i))
+
+		err := insertOne(ctx, dbPool, qp, doc.(*types.Document))
+
+		var we *commonerrors.WriteErrors
+
+		switch {
+		case err == nil:
+			inserted++
+			continue
+		case errors.As(err, &we):
+			insErrors.Merge(we, int32(i))
+		default:
+			insErrors.Append(err, int32(i))
+		}
+
+		if ordered {
+			return inserted, &insErrors
+		}
+	}
+
+	return inserted, &insErrors
+}
+
+// insertOne checks if database and collection exist, create them if needed and attempts to insertDocument the given doc.
+func insertOne(ctx context.Context, dbPool *hanadb.Pool, qp *hanadb.QueryParams, doc *types.Document) error {
+	toInsert := doc
+
+	if !toInsert.Has("_id") {
+		// Make a copy so that original document could be sent to the proxy as it is.
+		toInsert = doc.DeepCopy()
+
+		toInsert.Set("_id", types.NewObjectID())
+	}
+
+	err := dbPool.InsertOne(ctx, qp, toInsert)
+
+	switch {
+	case err == nil:
+		return nil
+	case errors.Is(err, hanadb.ErrInvalidCollectionName), errors.Is(err, hanadb.ErrInvalidDatabaseName):
+		msg := fmt.Sprintf("Invalid namespace: %s.%s", qp.DB, qp.Collection)
+		return commonerrors.NewCommandErrorMsg(commonerrors.ErrInvalidNamespace, msg)
+
+	// TODO: set up some sort of metadata table to keep track of '_ids' so we can track duplicates
+	/*case errors.Is(err, hanzdb.ErrUniqueViolation):
+	// TODO Extend message for non-_id unique indexes in https://github.com/FerretDB/FerretDB/issues/2045
+	idMasrshaled := must.NotFail(json.Marshal(must.NotFail(d.Get("_id"))))
+
+	return commonerrors.NewWriteErrorMsg(
+		commonerrors.ErrDuplicateKey,
+		fmt.Sprintf(
+			`E11000 duplicate key error collection: %s.%s index: _id_ dup key: { _id: %s }`,
+			qp.DB, qp.Collection, idMasrshaled,
+		),
+	)
+	*/
+	default:
+		return lazyerrors.Error(err)
+	}
 }

From ef673cb49579db063b8decd94c2cedad4aa3c6a6 Mon Sep 17 00:00:00 2001
From: Lorant Polya <lorant.polya@sap.com>
Date: Fri, 2 Jun 2023 10:46:53 -0700
Subject: [PATCH 2/6] Hana Insert Impl Basics linter fixes

---
 .golangci.yml                           | 5 ++++-
 internal/handlers/hana/hanadb/insert.go | 8 ++++----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index 5a386d279ff6..f7ea8cfc3661 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -169,13 +169,16 @@ issues:
       path: cmd/envtool
       text: pgdb
 
-    # only `pg` handler and `sqlite` backend can import `sjson` package, no other handlers or backends can do that
+    # only `pg` handler, `sqlite` backend, and 'hanadb' package can import `sjson` package, no other handlers or backends can do that
     - linters: [depguard]
       path: internal/handlers/pg
       text: sjson
     - linters: [depguard]
       path: internal/backends/sqlite
       test: sjson
+    - linters: [depguard]
+      path: internal/handlers/hana/hanadb
+      test: sjson
 
     # only `tigris` handler can import `tigrisdb` package, no other handler can do that
     - linters: [depguard]
diff --git a/internal/handlers/hana/hanadb/insert.go b/internal/handlers/hana/hanadb/insert.go
index 49b2dfc790dd..28ec4aba0136 100644
--- a/internal/handlers/hana/hanadb/insert.go
+++ b/internal/handlers/hana/hanadb/insert.go
@@ -23,7 +23,7 @@ import (
 	"github.com/FerretDB/FerretDB/internal/util/must"
 )
 
-// CreateSchema inserts a document into a collection in SAP HANA JSON Document Store.
+// InsertOne inserts a document into a collection in SAP HANA JSON Document Store.
 func (hanaPool *Pool) InsertOne(ctx context.Context, qp *QueryParams, doc *types.Document) error {
 	err := hanaPool.CreateSchemaIfNotExists(ctx, qp)
 
@@ -43,11 +43,11 @@ func (hanaPool *Pool) InsertOne(ctx context.Context, qp *QueryParams, doc *types
 		return err
 	}
 
-	return hanaPool.Insert(ctx, qp, doc)
+	return hanaPool.insert(ctx, qp, doc)
 }
 
-// CreateSchema inserts a document into a collection in SAP HANA JSON Document Store.
-func (hanaPool *Pool) Insert(ctx context.Context, qp *QueryParams, doc *types.Document) error {
+// insert inserts a document into a collection in SAP HANA JSON Document Store.
+func (hanaPool *Pool) insert(ctx context.Context, qp *QueryParams, doc *types.Document) error {
 	sqlStmt := fmt.Sprintf("insert into %q.%q values($1)", qp.DB, qp.Collection)
 
 	// sjson.MarshalSingleValue can be used because the Hana insert json format is just a json string

From dca2a74e59449f6d412415ecbe1e4cca22b53d82 Mon Sep 17 00:00:00 2001
From: Lorant Polya <lorant.polya@sap.com>
Date: Tue, 6 Jun 2023 10:03:15 -0700
Subject: [PATCH 3/6] Update linter

---
 .golangci.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.golangci.yml b/.golangci.yml
index 6f882caee867..e6ef30dd403b 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -41,6 +41,7 @@ linters-settings:
           - $all
           - "!**/internal/backends/sqlite/*.go"
           - "!**/internal/handlers/pg/pgdb/*.go"
+          - "!**/internal/handlers/hana/hanadb/*.go"
         deny:
           - pkg: github.com/FerretDB/FerretDB/internal/handlers/sjson
       pgdb:

From f35752891c154dc3fe64960a47703a9648a62ca6 Mon Sep 17 00:00:00 2001
From: Lorant Polya <lorant.polya@sap.com>
Date: Thu, 15 Jun 2023 17:07:58 -0700
Subject: [PATCH 4/6] implemented msg_listdatabases

---
 internal/handlers/hana/hanadb/collections.go | 26 ++++++
 internal/handlers/hana/hanadb/databases.go   | 92 ++++++++++++++++++-
 internal/handlers/hana/msg_listdatabases.go  | 97 +++++++++++++++++++-
 3 files changed, 213 insertions(+), 2 deletions(-)

diff --git a/internal/handlers/hana/hanadb/collections.go b/internal/handlers/hana/hanadb/collections.go
index 158b60d30521..03147e9bcc3d 100644
--- a/internal/handlers/hana/hanadb/collections.go
+++ b/internal/handlers/hana/hanadb/collections.go
@@ -18,6 +18,8 @@ import (
 	"context"
 	"errors"
 	"fmt"
+
+	"github.com/FerretDB/FerretDB/internal/util/lazyerrors"
 )
 
 // CreateCollection creates a new SAP HANA JSON Document Store collection.
@@ -55,3 +57,27 @@ func (hanaPool *Pool) DropCollection(ctx context.Context, qp *QueryParams) error
 
 	return getHanaErrorIfExists(err)
 }
+
+// CollectionSize calculates the size of the given collection.
+//
+// Returns 0 if schema or collection doesn't exist, otherwise returns its size.
+func (hanaPool *Pool) CollectionSize(ctx context.Context, qp *QueryParams) (int64, error) {
+	sqlStmt := "SELECT TABLE_SIZE FROM M_TABLES WHERE SCHEMA_NAME = $1 AND TABLE_NAME = $2 AND TABLE_TYPE = 'COLLECTION'"
+
+	var size any
+	if err := hanaPool.QueryRowContext(ctx, sqlStmt, qp.DB, qp.Collection).Scan(&size); err != nil {
+		return 0, lazyerrors.Error(err)
+	}
+
+	var collectionSize int64
+	switch size := size.(type) {
+	case int64:
+		collectionSize = size
+	case nil:
+		collectionSize = 0
+	default:
+		return 0, lazyerrors.Errorf("Got wrong type for tableSize. Got: %T", collectionSize)
+	}
+
+	return collectionSize, nil
+}
diff --git a/internal/handlers/hana/hanadb/databases.go b/internal/handlers/hana/hanadb/databases.go
index 614191a2be84..0f1420157888 100644
--- a/internal/handlers/hana/hanadb/databases.go
+++ b/internal/handlers/hana/hanadb/databases.go
@@ -18,11 +18,13 @@ import (
 	"context"
 	"errors"
 	"fmt"
+
+	"github.com/FerretDB/FerretDB/internal/util/lazyerrors"
 )
 
 // CreateSchema creates a schema in SAP HANA JSON Document Store.
 //
-//	Returns ErrSchemaAlreadyExist if schema already exists.
+// Returns ErrSchemaAlreadyExist if schema already exists.
 func (hanaPool *Pool) CreateSchema(ctx context.Context, qp *QueryParams) error {
 	sqlStmt := fmt.Sprintf("CREATE SCHEMA %q", qp.DB)
 
@@ -55,3 +57,91 @@ func (hanaPool *Pool) DropSchema(ctx context.Context, qp *QueryParams) error {
 
 	return getHanaErrorIfExists(err)
 }
+
+// ListSchemas lists all schemas that aren't related to Hana SYS schemas and SYS owner.
+func (hanaPool *Pool) ListSchemas(ctx context.Context) ([]string, error) {
+	const excludeSYS = "%SYS%"
+	sqlStmt := "SELECT SCHEMA_NAME FROM SCHEMAS WHERE SCHEMA_NAME NOT LIKE $1 AND SCHEMA_OWNER NOT LIKE $2"
+
+	rows, err := hanaPool.QueryContext(ctx, sqlStmt, excludeSYS, excludeSYS)
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+	defer rows.Close()
+
+	res := make([]string, 0, 2)
+
+	for rows.Next() {
+		var name string
+		if err = rows.Scan(&name); err != nil {
+			return nil, lazyerrors.Error(err)
+		}
+
+		res = append(res, name)
+	}
+
+	if err = rows.Err(); err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	return res, nil
+}
+
+// ListCollections lists all collections under a given schema.
+//
+// Returns an empty array if schema doesn't exist.
+func (hanaPool *Pool) ListCollections(ctx context.Context, qp *QueryParams) ([]string, error) {
+	sqlStmt := "SELECT TABLE_NAME FROM M_TABLES WHERE SCHEMA_NAME = $1 AND TABLE_TYPE = 'COLLECTION'"
+
+	rows, err := hanaPool.QueryContext(ctx, sqlStmt, qp.DB)
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+	defer rows.Close()
+
+	res := make([]string, 0, 2)
+
+	for rows.Next() {
+		var name string
+		if err = rows.Scan(&name); err != nil {
+			return nil, lazyerrors.Error(err)
+		}
+
+		res = append(res, name)
+	}
+
+	if err = rows.Err(); err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	return res, nil
+}
+
+// SchemaSize calculates the total size of collections under schema.
+//
+// Returns 0 if schema doesn't exist, otherwise returns its size.
+func (hanaPool *Pool) SchemaSize(ctx context.Context, qp *QueryParams) (int64, error) {
+	collections, err := hanaPool.ListCollections(ctx, qp)
+	if err != nil {
+		return 0, lazyerrors.Error(err)
+	}
+
+	qpCopy := QueryParams{
+		DB: qp.DB,
+	}
+
+	var totalSize int64
+
+	for _, collection := range collections {
+		qpCopy.Collection = collection
+		size, err := hanaPool.CollectionSize(ctx, &qpCopy)
+
+		if err != nil {
+			return 0, lazyerrors.Error(err)
+		}
+
+		totalSize += size
+	}
+
+	return totalSize, nil
+}
diff --git a/internal/handlers/hana/msg_listdatabases.go b/internal/handlers/hana/msg_listdatabases.go
index 5cb1a2139521..facd557f1426 100644
--- a/internal/handlers/hana/msg_listdatabases.go
+++ b/internal/handlers/hana/msg_listdatabases.go
@@ -17,11 +17,106 @@ package hana
 import (
 	"context"
 
+	"github.com/FerretDB/FerretDB/internal/handlers/common"
+	"github.com/FerretDB/FerretDB/internal/handlers/commonparams"
+	"github.com/FerretDB/FerretDB/internal/handlers/hana/hanadb"
+	"github.com/FerretDB/FerretDB/internal/types"
+	"github.com/FerretDB/FerretDB/internal/util/lazyerrors"
 	"github.com/FerretDB/FerretDB/internal/util/must"
 	"github.com/FerretDB/FerretDB/internal/wire"
 )
 
 // MsgListDatabases implements HandlerInterface.
 func (h *Handler) MsgListDatabases(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg, error) {
-	return nil, notImplemented(must.NotFail(msg.Document()).Command())
+	dbPool, err := h.DBPool(ctx)
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	document, err := msg.Document()
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	var filter *types.Document
+	if filter, err = common.GetOptionalParam(document, "filter", filter); err != nil {
+		return nil, err
+	}
+
+	common.Ignored(document, h.L, "comment", "authorizedDatabases")
+
+	databaseNames, err := dbPool.ListSchemas(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	var nameOnly bool
+	if v, _ := document.Get("nameOnly"); v != nil {
+		nameOnly, err = commonparams.GetBoolOptionalParam("nameOnly", v)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	var totalSize int64
+	databases := types.MakeArray(len(databaseNames))
+	qp := hanadb.QueryParams{}
+
+	for _, databaseName := range databaseNames {
+		qp.DB = databaseName
+
+		size, err := dbPool.SchemaSize(ctx, &qp)
+		if err != nil {
+			return nil, lazyerrors.Error(err)
+		}
+
+		totalSize += size
+
+		d := must.NotFail(types.NewDocument(
+			"name", databaseName,
+			"sizeOnDisk", size,
+			"empty", size == 0,
+		))
+
+		matches, err := common.FilterDocument(d, filter)
+		if err != nil {
+			return nil, err
+		}
+
+		if !matches {
+			continue
+		}
+
+		if nameOnly {
+			d = must.NotFail(types.NewDocument(
+				"name", databaseName,
+			))
+		}
+
+		databases.Append(d)
+	}
+
+	if nameOnly {
+		var reply wire.OpMsg
+		must.NoError(reply.SetSections(wire.OpMsgSection{
+			Documents: []*types.Document{must.NotFail(types.NewDocument(
+				"databases", databases,
+				"ok", float64(1),
+			))},
+		}))
+
+		return &reply, nil
+	}
+
+	var reply wire.OpMsg
+	must.NoError(reply.SetSections(wire.OpMsgSection{
+		Documents: []*types.Document{must.NotFail(types.NewDocument(
+			"databases", databases,
+			"totalSize", totalSize,
+			"totalSizeMb", totalSize/1024/1024,
+			"ok", float64(1),
+		))},
+	}))
+
+	return &reply, nil
 }

From e6441d999ed41dd107aa7d0205c63b184be01765 Mon Sep 17 00:00:00 2001
From: Lorant Polya <lorant.polya@sap.com>
Date: Tue, 20 Jun 2023 08:34:18 -0700
Subject: [PATCH 5/6] fixed linter issue

---
 internal/handlers/hana/hanadb/databases.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal/handlers/hana/hanadb/databases.go b/internal/handlers/hana/hanadb/databases.go
index 0f1420157888..80cf538d407c 100644
--- a/internal/handlers/hana/hanadb/databases.go
+++ b/internal/handlers/hana/hanadb/databases.go
@@ -134,8 +134,8 @@ func (hanaPool *Pool) SchemaSize(ctx context.Context, qp *QueryParams) (int64, e
 
 	for _, collection := range collections {
 		qpCopy.Collection = collection
-		size, err := hanaPool.CollectionSize(ctx, &qpCopy)
 
+		size, err := hanaPool.CollectionSize(ctx, &qpCopy)
 		if err != nil {
 			return 0, lazyerrors.Error(err)
 		}

From 328bbfedbd02f5f54d804e8fe178f8d7104d9b45 Mon Sep 17 00:00:00 2001
From: Alexey Palazhchenko <alexey.palazhchenko@ferretdb.io>
Date: Wed, 21 Jun 2023 17:14:10 +0400
Subject: [PATCH 6/6] Shard Hana tests too

---
 .github/workflows/go-trust.yml | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/go-trust.yml b/.github/workflows/go-trust.yml
index 5dc8c72ebc12..1b21ca25de5a 100644
--- a/.github/workflows/go-trust.yml
+++ b/.github/workflows/go-trust.yml
@@ -32,10 +32,16 @@ env:
 
 jobs:
   integration:
-    name: Integration ${{ matrix.name }}
+    name: Integration ${{ matrix.name }} ${{ matrix.shard_index }}/${{ matrix.shard_total }}
     runs-on:
       group: paid
-    timeout-minutes: 30
+    timeout-minutes: 20
+
+    # Do not run this job in parallel for any PR change or branch/tag push
+    # to save some resources.
+    concurrency:
+      group: ${{ github.workflow }}-${{ matrix.name }}-${{ matrix.shard_index }}-${{ github.head_ref || github.ref_name }}
+      cancel-in-progress: true
 
     if: >
       github.event_name != 'pull_request_target' ||
@@ -48,7 +54,9 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - { name: "Hana", task: "hana" }
+          - { name: "Hana", task: "hana", shard_index: 1, shard_total: 3 }
+          - { name: "Hana", task: "hana", shard_index: 2, shard_total: 3 }
+          - { name: "Hana", task: "hana", shard_index: 3, shard_total: 3 }
 
     steps:
       - name: Checkout code
@@ -90,8 +98,8 @@ jobs:
       - name: Wait for and setup environment
         run: bin/task env-setup
 
-      - name: Run ${{ matrix.task }} tests
-        run: bin/task test-integration-${{ matrix.task }}
+      - name: Run ${{ matrix.name }} tests (${{ matrix.shard_index }}/${{ matrix.shard_total }})
+        run: bin/task test-integration-${{ matrix.task }} SHARD_INDEX=${{ matrix.shard_index }} SHARD_TOTAL=${{ matrix.shard_total }}
         env:
           GOFLAGS: ${{ runner.debug == '1' && '-v' || '' }}
           FERRETDB_HANA_URL: ${{ secrets.FERRETDB_HANA_URL }}
@@ -108,7 +116,7 @@ jobs:
         with:
           token: 22159d7c-856d-4fe9-8fdb-5d9ecff35514
           files: ./integration/integration-${{ matrix.task }}.txt
-          flags: integration,${{ matrix.task }}
+          flags: integration,${{ matrix.task }},shard-${{ matrix.shard_index }}
           fail_ci_if_error: true
           verbose: true