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connect: reduce allocations when building SET command #1111

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merged 2 commits into from May 29, 2020
Merged

connect: reduce allocations when building SET command #1111

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5748e04
connect: reduce allocations when building SET command
dolmen May 22, 2020
acb481b
handleParams: use strings.Builder instead of direct []byte
dolmen May 27, 2020
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19 changes: 14 additions & 5 deletions connection.go
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Expand Up @@ -47,7 +47,7 @@ type mysqlConn struct {

// Handles parameters set in DSN after the connection is established
func (mc *mysqlConn) handleParams() (err error) {
var params []string
var cmdSet strings.Builder
for param, val := range mc.cfg.Params {
switch param {
// Charset: character_set_connection, character_set_client, character_set_results
Expand All @@ -64,14 +64,23 @@ func (mc *mysqlConn) handleParams() (err error) {
return
}

// Other system vars
// Other system vars accumulated in a single SET command
default:
params = append(params, param+"="+val)
if cmdSet.Len() == 0 {
// Heuristic: 29 chars for each other key=value to reduce reallocations
cmdSet.Grow(4 + len(param) + 1 + len(val) + 30*(len(mc.cfg.Params)-1))
cmdSet.WriteString("SET ")
} else {
cmdSet.WriteByte(',')
}
cmdSet.WriteString(param)
cmdSet.WriteByte('=')
cmdSet.WriteString(val)
}
}

if len(params) > 0 {
err = mc.exec("SET " + strings.Join(params, ","))
if cmdSet.Len() > 0 {
err = mc.exec(cmdSet.String())
if err != nil {
return
}
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