1. 实现配置文件解析

2. 实现数据库连接

vendor/github.com/jackc/pgx/v5/extended_query_builder.go

@@ -0,0 +1,218 @@
+package pgx
+
+import (
+	"database/sql/driver"
+	"fmt"
+
+	"github.com/jackc/pgx/v5/internal/anynil"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+// ExtendedQueryBuilder is used to choose the parameter formats, to format the parameters and to choose the result
+// formats for an extended query.
+type ExtendedQueryBuilder struct {
+	ParamValues     [][]byte
+	paramValueBytes []byte
+	ParamFormats    []int16
+	ResultFormats   []int16
+}
+
+// Build sets ParamValues, ParamFormats, and ResultFormats for use with *PgConn.ExecParams or *PgConn.ExecPrepared. If
+// sd is nil then QueryExecModeExec behavior will be used.
+func (eqb *ExtendedQueryBuilder) Build(m *pgtype.Map, sd *pgconn.StatementDescription, args []any) error {
+	eqb.reset()
+
+	anynil.NormalizeSlice(args)
+
+	if sd == nil {
+		return eqb.appendParamsForQueryExecModeExec(m, args)
+	}
+
+	if len(sd.ParamOIDs) != len(args) {
+		return fmt.Errorf("mismatched param and argument count")
+	}
+
+	for i := range args {
+		err := eqb.appendParam(m, sd.ParamOIDs[i], -1, args[i])
+		if err != nil {
+			err = fmt.Errorf("failed to encode args[%d]: %v", i, err)
+			return err
+		}
+	}
+
+	for i := range sd.Fields {
+		eqb.appendResultFormat(m.FormatCodeForOID(sd.Fields[i].DataTypeOID))
+	}
+
+	return nil
+}
+
+// appendParam appends a parameter to the query. format may be -1 to automatically choose the format. If arg is nil it
+// must be an untyped nil.
+func (eqb *ExtendedQueryBuilder) appendParam(m *pgtype.Map, oid uint32, format int16, arg any) error {
+	if format == -1 {
+		preferredFormat := eqb.chooseParameterFormatCode(m, oid, arg)
+		preferredErr := eqb.appendParam(m, oid, preferredFormat, arg)
+		if preferredErr == nil {
+			return nil
+		}
+
+		var otherFormat int16
+		if preferredFormat == TextFormatCode {
+			otherFormat = BinaryFormatCode
+		} else {
+			otherFormat = TextFormatCode
+		}
+
+		otherErr := eqb.appendParam(m, oid, otherFormat, arg)
+		if otherErr == nil {
+			return nil
+		}
+
+		return preferredErr // return the error from the preferred format
+	}
+
+	v, err := eqb.encodeExtendedParamValue(m, oid, format, arg)
+	if err != nil {
+		return err
+	}
+
+	eqb.ParamFormats = append(eqb.ParamFormats, format)
+	eqb.ParamValues = append(eqb.ParamValues, v)
+
+	return nil
+}
+
+// appendResultFormat appends a result format to the query.
+func (eqb *ExtendedQueryBuilder) appendResultFormat(format int16) {
+	eqb.ResultFormats = append(eqb.ResultFormats, format)
+}
+
+// reset readies eqb to build another query.
+func (eqb *ExtendedQueryBuilder) reset() {
+	eqb.ParamValues = eqb.ParamValues[0:0]
+	eqb.paramValueBytes = eqb.paramValueBytes[0:0]
+	eqb.ParamFormats = eqb.ParamFormats[0:0]
+	eqb.ResultFormats = eqb.ResultFormats[0:0]
+
+	if cap(eqb.ParamValues) > 64 {
+		eqb.ParamValues = make([][]byte, 0, 64)
+	}
+
+	if cap(eqb.paramValueBytes) > 256 {
+		eqb.paramValueBytes = make([]byte, 0, 256)
+	}
+
+	if cap(eqb.ParamFormats) > 64 {
+		eqb.ParamFormats = make([]int16, 0, 64)
+	}
+	if cap(eqb.ResultFormats) > 64 {
+		eqb.ResultFormats = make([]int16, 0, 64)
+	}
+}
+
+func (eqb *ExtendedQueryBuilder) encodeExtendedParamValue(m *pgtype.Map, oid uint32, formatCode int16, arg any) ([]byte, error) {
+	if anynil.Is(arg) {
+		return nil, nil
+	}
+
+	if eqb.paramValueBytes == nil {
+		eqb.paramValueBytes = make([]byte, 0, 128)
+	}
+
+	pos := len(eqb.paramValueBytes)
+
+	buf, err := m.Encode(oid, formatCode, arg, eqb.paramValueBytes)
+	if err != nil {
+		return nil, err
+	}
+	if buf == nil {
+		return nil, nil
+	}
+	eqb.paramValueBytes = buf
+	return eqb.paramValueBytes[pos:], nil
+}
+
+// chooseParameterFormatCode determines the correct format code for an
+// argument to a prepared statement. It defaults to TextFormatCode if no
+// determination can be made.
+func (eqb *ExtendedQueryBuilder) chooseParameterFormatCode(m *pgtype.Map, oid uint32, arg any) int16 {
+	switch arg.(type) {
+	case string, *string:
+		return TextFormatCode
+	}
+
+	return m.FormatCodeForOID(oid)
+}
+
+// appendParamsForQueryExecModeExec appends the args to eqb.
+//
+// Parameters must be encoded in the text format because of differences in type conversion between timestamps and
+// dates. In QueryExecModeExec we don't know what the actual PostgreSQL type is. To determine the type we use the
+// Go type to OID type mapping registered by RegisterDefaultPgType. However, the Go time.Time represents both
+// PostgreSQL timestamp[tz] and date. To use the binary format we would need to also specify what the PostgreSQL
+// type OID is. But that would mean telling PostgreSQL that we have sent a timestamp[tz] when what is needed is a date.
+// This means that the value is converted from text to timestamp[tz] to date. This means it does a time zone conversion
+// before converting it to date. This means that dates can be shifted by one day. In text format without that double
+// type conversion it takes the date directly and ignores time zone (i.e. it works).
+//
+// Given that the whole point of QueryExecModeExec is to operate without having to know the PostgreSQL types there is
+// no way to safely use binary or to specify the parameter OIDs.
+func (eqb *ExtendedQueryBuilder) appendParamsForQueryExecModeExec(m *pgtype.Map, args []any) error {
+	for _, arg := range args {
+		if arg == nil {
+			err := eqb.appendParam(m, 0, TextFormatCode, arg)
+			if err != nil {
+				return err
+			}
+		} else {
+			dt, ok := m.TypeForValue(arg)
+			if !ok {
+				var tv pgtype.TextValuer
+				if tv, ok = arg.(pgtype.TextValuer); ok {
+					t, err := tv.TextValue()
+					if err != nil {
+						return err
+					}
+
+					dt, ok = m.TypeForOID(pgtype.TextOID)
+					if ok {
+						arg = t
+					}
+				}
+			}
+			if !ok {
+				var dv driver.Valuer
+				if dv, ok = arg.(driver.Valuer); ok {
+					v, err := dv.Value()
+					if err != nil {
+						return err
+					}
+					dt, ok = m.TypeForValue(v)
+					if ok {
+						arg = v
+					}
+				}
+			}
+			if !ok {
+				var str fmt.Stringer
+				if str, ok = arg.(fmt.Stringer); ok {
+					dt, ok = m.TypeForOID(pgtype.TextOID)
+					if ok {
+						arg = str.String()
+					}
+				}
+			}
+			if !ok {
+				return &unknownArgumentTypeQueryExecModeExecError{arg: arg}
+			}
+			err := eqb.appendParam(m, dt.OID, TextFormatCode, arg)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}