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Fix unnecessary cancel requests #136

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Fix unnecessary cancel requests #136

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bc0714d
fix useless cancel requests
Flgado Mar 3, 2025
85f90ad
remove uneccessary validation. Only create header if nextUri exist
Flgado Mar 3, 2025
279be2a
Add test for QueryRow handling of FINISHED state
Flgado Mar 15, 2025
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65 changes: 43 additions & 22 deletions trino/trino.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1138,27 +1138,34 @@ func (qr *driverRows) Close() error {
if qr.err == sql.ErrNoRows || qr.err == io.EOF {
return nil
}

qr.err = io.EOF
hs := make(http.Header)
if qr.stmt.user != "" {
hs.Add(trinoUserHeader, qr.stmt.user)
}
ctx, cancel := context.WithTimeout(context.WithoutCancel(qr.ctx), DefaultCancelQueryTimeout)
defer cancel()
req, err := qr.stmt.conn.newRequest(ctx, "DELETE", qr.stmt.conn.baseURL+"/v1/query/"+url.PathEscape(qr.queryID), nil, hs)
if err != nil {
return err
}
resp, err := qr.stmt.conn.roundTrip(ctx, req)
if err != nil {
qferr, ok := err.(*ErrQueryFailed)
if ok && qferr.StatusCode == http.StatusNoContent {
qr.nextURI = ""
return nil

if qr.nextURI != "" {
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Reverse this condition and do an early return to avoid indenting the remaining code.

hs := make(http.Header)
if qr.stmt.user != "" {
hs.Add(trinoUserHeader, qr.stmt.user)
}
return err

ctx, cancel := context.WithTimeout(context.WithoutCancel(qr.ctx), DefaultCancelQueryTimeout)
defer cancel()
req, err := qr.stmt.conn.newRequest(ctx, "DELETE", qr.nextURI, nil, hs)
if err != nil {
return err
}
resp, err := qr.stmt.conn.roundTrip(ctx, req)
if err != nil {
qferr, ok := err.(*ErrQueryFailed)
if ok && qferr.StatusCode == http.StatusNoContent {
qr.nextURI = ""
return nil
}
return err
}
resp.Body.Close()

}
resp.Body.Close()

return qr.err
}

Expand Down Expand Up @@ -1205,6 +1212,7 @@ func (qr *driverRows) Next(dest []driver.Value) error {
if qr.err != nil {
return qr.err
}

if qr.columns == nil || qr.rowindex >= len(qr.data) {
if qr.nextURI == "" {
qr.err = io.EOF
Expand All @@ -1215,22 +1223,34 @@ func (qr *driverRows) Next(dest []driver.Value) error {
return err
}
}

if len(qr.coltype) == 0 {
qr.err = sql.ErrNoRows
return qr.err
}
for i, v := range qr.coltype {
if i > len(dest)-1 {

row := qr.data[qr.rowindex]
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Move any refactor not directly related to the issue this PR fixes to a separate commit.

for i, colType := range qr.coltype {
if i >= len(dest) {
break
}
vv, err := v.ConvertValue(qr.data[qr.rowindex][i])
val, err := colType.ConvertValue(row[i])
if err != nil {
qr.err = err
return err
}
dest[i] = vv
dest[i] = val
}

qr.rowindex++

// Prefetch next set of rows
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Useless comment - it explains the what, which is pretty obvious, but not the why, which is not. Why do we need to do this? If the user doesn't request any more data, we'll waste resources on one round-trip.

Can we do this only when cancelling the query?

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I have to rethink this PR. Now that I'm more familiar with the project, we can't approach it this way—it's a bit of a mess.
I'll work on it. Thanks!

if qr.rowindex == len(qr.data) && qr.nextURI != "" {
if err := qr.fetch(); err != nil {
qr.err = err
}
}

return nil
}

Expand Down Expand Up @@ -1330,6 +1350,7 @@ func (qr *driverRows) fetch() error {
return err
}
qr.rowindex = 0
qr.nextURI = qresp.NextURI
qr.data = qresp.Data
qr.rowsAffected = qresp.UpdateCount
qr.scheduleProgressUpdate(qresp.ID, qresp.Stats)
Expand Down
195 changes: 195 additions & 0 deletions trino/trino_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1973,3 +1973,198 @@ func TestForwardAuthorizationHeader(t *testing.T) {

assert.NoError(t, db.Close())
}

func TestPagination(t *testing.T) {
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Can you come up with a better name? I'm not sure what this test is for.

var buf, buf2, buf3 *bytes.Buffer
var ts *httptest.Server
ts = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.URL.Path == "/v1/statement" {
if buf == nil {
buf = new(bytes.Buffer)

json.NewEncoder(buf).Encode(&stmtResponse{
ID: "fake-query",
NextURI: ts.URL + "/v1/statement/20210817_140827_00000_arvdv/1",
Stats: stmtStats{
State: "QUEUED",
},
})
}
w.WriteHeader(http.StatusOK)
w.Write(buf.Bytes())
return
}

if r.URL.Path == "/v1/statement/20210817_140827_00000_arvdv/1" {
if buf2 == nil {
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Why are separate buffers needed here? Can we initialize them early, and remove this condition?

buf2 = new(bytes.Buffer)
json.NewEncoder(buf2).Encode(&queryResponse{
ID: "fake-query",
NextURI: ts.URL + "/v1/statement/20210817_140827_00000_arvdv/2",
Columns: []queryColumn{
{
Name: "_col0",
Type: "integer",
TypeSignature: typeSignature{
RawType: "integer",
Arguments: []typeArgument{},
},
},
},
Data: []queryData{
{1},
},
Stats: stmtStats{
State: "FINISHED",
},
})
}
w.WriteHeader(http.StatusOK)
w.Write(buf2.Bytes())
return
}

if r.URL.Path == "/v1/statement/20210817_140827_00000_arvdv/2" {
if buf3 == nil {
buf3 = new(bytes.Buffer)
json.NewEncoder(buf3).Encode(&queryResponse{
ID: "fake-query",
Columns: []queryColumn{
{
Name: "_col1",
Type: "integer",
TypeSignature: typeSignature{
RawType: "integer",
Arguments: []typeArgument{},
},
},
},
Data: []queryData{
{2},
},
Stats: stmtStats{
State: "FINISHED",
},
})
}
w.WriteHeader(http.StatusOK)
w.Write(buf3.Bytes())
return
}

w.WriteHeader(http.StatusInternalServerError)
json.NewEncoder(w).Encode(ErrTrino{ErrorName: "Unexpected request"})
}))

defer ts.Close()

db, err := sql.Open("trino", ts.URL)
require.NoError(t, err)
defer db.Close()

// Run a query
rows, err := db.Query("SELECT 1")

var results []int
for rows.Next() {
var value int
err := rows.Scan(&value)
require.NoError(t, err)
results = append(results, value)
}

// Ensure no error in iteration
require.NoError(t, rows.Err())

// Assert expected results
assert.Equal(t, []int{1, 2}, results, "Expected query results to match")
}

func TestQuerySingleRowDoesNotTriggerDeleteRequest(t *testing.T) {
var buf, buf2, buf3 *bytes.Buffer
var ts *httptest.Server
var methodUsed string

ts = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.URL.Path == "/v1/statement" {
if buf == nil {
buf = new(bytes.Buffer)

json.NewEncoder(buf).Encode(&stmtResponse{
ID: "fake-query",
NextURI: ts.URL + "/v1/statement/20210817_140827_00000_arvdv/1",
Stats: stmtStats{
State: "QUEUED",
},
})
}
w.WriteHeader(http.StatusOK)
w.Write(buf.Bytes())
return
}

if r.URL.Path == "/v1/statement/20210817_140827_00000_arvdv/1" {
if buf2 == nil {
buf2 = new(bytes.Buffer)
json.NewEncoder(buf2).Encode(&queryResponse{
ID: "fake-query",
NextURI: ts.URL + "/v1/statement/20210817_140827_00000_arvdv/2",
Columns: []queryColumn{
{
Name: "_col0",
Type: "integer",
TypeSignature: typeSignature{
RawType: "integer",
Arguments: []typeArgument{},
},
},
},
Data: []queryData{
{1},
},
Stats: stmtStats{
State: "FINISHED",
},
})
}
w.WriteHeader(http.StatusOK)
w.Write(buf2.Bytes())
return
}

if r.URL.Path == "/v1/statement/20210817_140827_00000_arvdv/2" {
methodUsed = r.Method

if buf3 == nil {
buf3 = new(bytes.Buffer)
json.NewEncoder(buf3).Encode(&queryResponse{
Stats: stmtStats{
State: "FINISHED",
},
})
}
w.WriteHeader(http.StatusOK)
w.Write(buf3.Bytes())
return
}

w.WriteHeader(http.StatusInternalServerError)
json.NewEncoder(w).Encode(ErrTrino{ErrorName: "Unexpected request"})
}))

defer ts.Close()

db, err := sql.Open("trino", ts.URL)
require.NoError(t, err)
defer db.Close()

var v int

err = db.QueryRow("SELECT 1").Scan(&v)

require.NoError(t, err)

assert.Equal(t, 1, v, "Expected query results to match")

assert.NotEqual(t, http.MethodDelete, methodUsed, "Expected HTTP method to be GET")
}