Improved the performance of CopyIn and CopyInSchema and added BufferQuoteIdentifier (#1100)

conn.go

@@ -2,6 +2,7 @@ package pq
 
 import (
 	"bufio"
+	"bytes"
 	"context"
 	"crypto/md5"
 	"crypto/sha256"
@@ -1631,10 +1632,10 @@ func (rs *rows) NextResultSet() error {
 // QuoteIdentifier quotes an "identifier" (e.g. a table or a column name) to be
 // used as part of an SQL statement.  For example:
 //
-//    tblname := "my_table"
-//    data := "my_data"
-//    quoted := pq.QuoteIdentifier(tblname)
-//    err := db.Exec(fmt.Sprintf("INSERT INTO %s VALUES ($1)", quoted), data)
+//	tblname := "my_table"
+//	data := "my_data"
+//	quoted := pq.QuoteIdentifier(tblname)
+//	err := db.Exec(fmt.Sprintf("INSERT INTO %s VALUES ($1)", quoted), data)
 //
 // Any double quotes in name will be escaped.  The quoted identifier will be
 // case sensitive when used in a query.  If the input string contains a zero
@@ -1647,12 +1648,24 @@ func QuoteIdentifier(name string) string {
 	return `"` + strings.Replace(name, `"`, `""`, -1) + `"`
 }
 
+// BufferQuoteIdentifier satisfies the same purpose as QuoteIdentifier, but backed by a
+// byte buffer.
+func BufferQuoteIdentifier(name string, buffer *bytes.Buffer) {
+	end := strings.IndexRune(name, 0)
+	if end > -1 {
+		name = name[:end]
+	}
+	buffer.WriteRune('"')
+	buffer.WriteString(strings.Replace(name, `"`, `""`, -1))
+	buffer.WriteRune('"')
+}
+
 // QuoteLiteral quotes a 'literal' (e.g. a parameter, often used to pass literal
 // to DDL and other statements that do not accept parameters) to be used as part
 // of an SQL statement.  For example:
 //
-//    exp_date := pq.QuoteLiteral("2023-01-05 15:00:00Z")
-//    err := db.Exec(fmt.Sprintf("CREATE ROLE my_user VALID UNTIL %s", exp_date))
+//	exp_date := pq.QuoteLiteral("2023-01-05 15:00:00Z")
+//	err := db.Exec(fmt.Sprintf("CREATE ROLE my_user VALID UNTIL %s", exp_date))
 //
 // Any single quotes in name will be escaped. Any backslashes (i.e. "\") will be
 // replaced by two backslashes (i.e. "\\") and the C-style escape identifier

copy.go

@@ -1,6 +1,7 @@
 package pq
 
 import (
+	"bytes"
 	"context"
 	"database/sql/driver"
 	"encoding/binary"
@@ -20,29 +21,35 @@ var (
 // CopyIn creates a COPY FROM statement which can be prepared with
 // Tx.Prepare().  The target table should be visible in search_path.
 func CopyIn(table string, columns ...string) string {
-	stmt := "COPY " + QuoteIdentifier(table) + " ("
+	buffer := bytes.NewBufferString("COPY ")
+	BufferQuoteIdentifier(table, buffer)
+	buffer.WriteString(" (")
+	makeStmt(buffer, columns...)
+	return buffer.String()
+}
+
+// MakeStmt makes the stmt string for CopyIn and CopyInSchema.
+func makeStmt(buffer *bytes.Buffer, columns ...string) {
+	//s := bytes.NewBufferString()
 	for i, col := range columns {
 		if i != 0 {
-			stmt += ", "
+			buffer.WriteString(", ")
 		}
-		stmt += QuoteIdentifier(col)
+		BufferQuoteIdentifier(col, buffer)
 	}
-	stmt += ") FROM STDIN"
-	return stmt
+	buffer.WriteString(") FROM STDIN")
 }
 
 // CopyInSchema creates a COPY FROM statement which can be prepared with
 // Tx.Prepare().
 func CopyInSchema(schema, table string, columns ...string) string {
-	stmt := "COPY " + QuoteIdentifier(schema) + "." + QuoteIdentifier(table) + " ("
-	for i, col := range columns {
-		if i != 0 {
-			stmt += ", "
-		}
-		stmt += QuoteIdentifier(col)
-	}
-	stmt += ") FROM STDIN"
-	return stmt
+	buffer := bytes.NewBufferString("COPY ")
+	BufferQuoteIdentifier(schema, buffer)
+	buffer.WriteRune('.')
+	BufferQuoteIdentifier(table, buffer)
+	buffer.WriteString(" (")
+	makeStmt(buffer, columns...)
+	return buffer.String()
 }
 
 type copyin struct {