147 lines
3.8 KiB
Go
147 lines
3.8 KiB
Go
package pgx
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import (
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"fmt"
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"github.com/jackc/pgx/v5/pgconn"
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"github.com/jackc/pgx/v5/pgtype"
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)
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// ExtendedQueryBuilder is used to choose the parameter formats, to format the parameters and to choose the result
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// formats for an extended query.
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type ExtendedQueryBuilder struct {
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ParamValues [][]byte
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paramValueBytes []byte
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ParamFormats []int16
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ResultFormats []int16
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}
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// Build sets ParamValues, ParamFormats, and ResultFormats for use with *PgConn.ExecParams or *PgConn.ExecPrepared. If
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// sd is nil then QueryExecModeExec behavior will be used.
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func (eqb *ExtendedQueryBuilder) Build(m *pgtype.Map, sd *pgconn.StatementDescription, args []any) error {
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eqb.reset()
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if sd == nil {
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for i := range args {
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err := eqb.appendParam(m, 0, pgtype.TextFormatCode, args[i])
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if err != nil {
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err = fmt.Errorf("failed to encode args[%d]: %w", i, err)
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return err
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}
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}
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return nil
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}
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if len(sd.ParamOIDs) != len(args) {
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return fmt.Errorf("mismatched param and argument count")
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}
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for i := range args {
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err := eqb.appendParam(m, sd.ParamOIDs[i], -1, args[i])
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if err != nil {
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err = fmt.Errorf("failed to encode args[%d]: %w", i, err)
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return err
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}
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}
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for i := range sd.Fields {
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eqb.appendResultFormat(m.FormatCodeForOID(sd.Fields[i].DataTypeOID))
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}
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return nil
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}
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// appendParam appends a parameter to the query. format may be -1 to automatically choose the format. If arg is nil it
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// must be an untyped nil.
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func (eqb *ExtendedQueryBuilder) appendParam(m *pgtype.Map, oid uint32, format int16, arg any) error {
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if format == -1 {
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preferredFormat := eqb.chooseParameterFormatCode(m, oid, arg)
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preferredErr := eqb.appendParam(m, oid, preferredFormat, arg)
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if preferredErr == nil {
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return nil
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}
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var otherFormat int16
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if preferredFormat == TextFormatCode {
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otherFormat = BinaryFormatCode
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} else {
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otherFormat = TextFormatCode
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}
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otherErr := eqb.appendParam(m, oid, otherFormat, arg)
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if otherErr == nil {
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return nil
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}
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return preferredErr // return the error from the preferred format
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}
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v, err := eqb.encodeExtendedParamValue(m, oid, format, arg)
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if err != nil {
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return err
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}
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eqb.ParamFormats = append(eqb.ParamFormats, format)
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eqb.ParamValues = append(eqb.ParamValues, v)
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return nil
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}
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// appendResultFormat appends a result format to the query.
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func (eqb *ExtendedQueryBuilder) appendResultFormat(format int16) {
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eqb.ResultFormats = append(eqb.ResultFormats, format)
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}
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// reset readies eqb to build another query.
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func (eqb *ExtendedQueryBuilder) reset() {
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eqb.ParamValues = eqb.ParamValues[0:0]
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eqb.paramValueBytes = eqb.paramValueBytes[0:0]
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eqb.ParamFormats = eqb.ParamFormats[0:0]
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eqb.ResultFormats = eqb.ResultFormats[0:0]
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if cap(eqb.ParamValues) > 64 {
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eqb.ParamValues = make([][]byte, 0, 64)
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}
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if cap(eqb.paramValueBytes) > 256 {
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eqb.paramValueBytes = make([]byte, 0, 256)
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}
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if cap(eqb.ParamFormats) > 64 {
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eqb.ParamFormats = make([]int16, 0, 64)
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}
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if cap(eqb.ResultFormats) > 64 {
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eqb.ResultFormats = make([]int16, 0, 64)
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}
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}
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func (eqb *ExtendedQueryBuilder) encodeExtendedParamValue(m *pgtype.Map, oid uint32, formatCode int16, arg any) ([]byte, error) {
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if eqb.paramValueBytes == nil {
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eqb.paramValueBytes = make([]byte, 0, 128)
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}
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pos := len(eqb.paramValueBytes)
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buf, err := m.Encode(oid, formatCode, arg, eqb.paramValueBytes)
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if err != nil {
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return nil, err
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}
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if buf == nil {
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return nil, nil
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}
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eqb.paramValueBytes = buf
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return eqb.paramValueBytes[pos:], nil
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}
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// chooseParameterFormatCode determines the correct format code for an
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// argument to a prepared statement. It defaults to TextFormatCode if no
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// determination can be made.
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func (eqb *ExtendedQueryBuilder) chooseParameterFormatCode(m *pgtype.Map, oid uint32, arg any) int16 {
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switch arg.(type) {
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case string, *string:
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return TextFormatCode
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}
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return m.FormatCodeForOID(oid)
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}
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