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Optimize large result sets

pull/745/head
Jack Christensen 2020-05-09 23:57:20 -05:00
parent e3519cfd75
commit aabe5538a8
3 changed files with 41 additions and 5 deletions
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2
go.mod
View File

@ -9,7 +9,7 @@ require (
github.com/jackc/pgconn v1.5.0
github.com/jackc/pgio v1.0.0
github.com/jackc/pgproto3/v2 v2.0.1
github.com/jackc/pgtype v1.3.1-0.20200508211315-97bbe6ae20e2
github.com/jackc/pgtype v1.3.1-0.20200510045248-7e66ab1e146c
github.com/jackc/puddle v1.1.1
github.com/rs/zerolog v1.15.0
github.com/shopspring/decimal v0.0.0-20200227202807-02e2044944cc

2
go.sum
View File

@ -57,6 +57,8 @@ github.com/jackc/pgtype v1.3.1-0.20200505182314-3b7c47a2a7da h1:ZbfsOjqJ1nHsryU0
github.com/jackc/pgtype v1.3.1-0.20200505182314-3b7c47a2a7da/go.mod h1:vaogEUkALtxZMCH411K+tKzNpwzCKU+AnPzBKZ+I+Po=
github.com/jackc/pgtype v1.3.1-0.20200508211315-97bbe6ae20e2 h1:Y6cErz3hUojOwnjUEWoZPRCBQcB7avM9ntGiYkB0wJo=
github.com/jackc/pgtype v1.3.1-0.20200508211315-97bbe6ae20e2/go.mod h1:vaogEUkALtxZMCH411K+tKzNpwzCKU+AnPzBKZ+I+Po=
github.com/jackc/pgtype v1.3.1-0.20200510045248-7e66ab1e146c h1:id5j6vOwHhbR7BYdGyb0sDMQjNsKTO+mXWaJxiwKu5M=
github.com/jackc/pgtype v1.3.1-0.20200510045248-7e66ab1e146c/go.mod h1:vaogEUkALtxZMCH411K+tKzNpwzCKU+AnPzBKZ+I+Po=
github.com/jackc/pgx/v4 v4.0.0-20190420224344-cc3461e65d96/go.mod h1:mdxmSJJuR08CZQyj1PVQBHy9XOp5p8/SHH6a0psbY9Y=
github.com/jackc/pgx/v4 v4.0.0-20190421002000-1b8f0016e912/go.mod h1:no/Y67Jkk/9WuGR0JG/JseM9irFbnEPbuWV2EELPNuM=
github.com/jackc/pgx/v4 v4.0.0-pre1.0.20190824185557-6972a5742186/go.mod h1:X+GQnOEnf1dqHGpw7JmHqHc1NxDoalibchSk9/RWuDc=

42
rows.go
View File

@ -109,6 +109,9 @@ type connRows struct {
resultReader *pgconn.ResultReader
multiResultReader *pgconn.MultiResultReader
scanPlans []pgtype.ScanPlan
dstValues []interface{}
}
func (rows *connRows) FieldDescriptions() []pgproto3.FieldDescription {
@ -184,11 +187,43 @@ func (rows *connRows) Next() bool {
}
func (rows *connRows) Scan(dest ...interface{}) error {
err := ScanRow(rows.connInfo, rows.FieldDescriptions(), rows.values, dest...)
if err != nil {
ci := rows.connInfo
fieldDescriptions := rows.FieldDescriptions()
values := rows.values
if len(fieldDescriptions) != len(values) {
err := errors.Errorf("number of field descriptions must equal number of values, got %d and %d", len(fieldDescriptions), len(values))
rows.fatal(err)
return err
}
if len(fieldDescriptions) != len(dest) {
err := errors.Errorf("number of field descriptions must equal number of destinations, got %d and %d", len(fieldDescriptions), len(dest))
rows.fatal(err)
return err
}
if rows.scanPlans == nil {
rows.scanPlans = make([]pgtype.ScanPlan, len(values))
rows.dstValues = make([]interface{}, len(values))
}
for i, dst := range dest {
if dst == nil {
continue
}
if dst != rows.dstValues[i] {
rows.scanPlans[i] = ci.PlanScan(fieldDescriptions[i].DataTypeOID, fieldDescriptions[i].Format, values[i], dest[i])
rows.dstValues[i] = dst
}
err := rows.scanPlans[i].Scan(ci, fieldDescriptions[i].DataTypeOID, fieldDescriptions[i].Format, values[i], dst)
if err != nil {
err = scanArgError{col: i, err: err}
rows.fatal(err)
return err
}
}
return nil
}
@ -278,8 +313,7 @@ func (e scanArgError) Error() string {
return fmt.Sprintf("can't scan into dest[%d]: %v", e.col, e.err)
}
// ScanRow decodes raw row data into dest. This is a low level function used internally to to implement the Rows
// interface Scan method. It can be used to scan rows read from the lower level pgconn interface.
// ScanRow decodes raw row data into dest. It can be used to scan rows read from the lower level pgconn interface.
//
// connInfo - OID to Go type mapping.
// fieldDescriptions - OID and format of values