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query.go
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query.go
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package pgsrv
import (
"context"
"database/sql/driver"
"fmt"
parser "github.com/lfittl/pg_query_go"
nodes "github.com/lfittl/pg_query_go/nodes"
"github.com/panoplyio/pgsrv/protocol"
"io"
)
type query struct {
transport *protocol.Transport
queryer Queryer
execer Execer
sql string
numCols int
}
// Run the query using the Server's defined queryer
func (q *query) Run(sess Session) error {
// parse the query
ast, err := parser.Parse(q.sql)
if err != nil {
return q.transport.Write(protocol.ErrorResponse(err))
}
// add the session to the context, cast to the Session interface just for
// compile time verification that the interface is implemented.
ctx := context.Background()
ctx = context.WithValue(ctx, sessionCtxKey, sess)
ctx = context.WithValue(ctx, sqlCtxKey, q.sql)
ctx = context.WithValue(ctx, astCtxKey, ast)
// execute all of the statements
for _, stmt := range ast.Statements {
rawStmt, isRaw := stmt.(nodes.RawStmt)
if isRaw {
stmt = rawStmt.Stmt
}
// determine if it's a query or command
switch v := stmt.(type) {
case nodes.PrepareStmt:
s, ok := sess.(*session)
// only session implementation is capable of storing prepared stmts
if ok {
// we just store the statement and don't do anything
s.storePreparedStatement(&v)
} else {
return Unsupported("prepared statements")
}
case nodes.SelectStmt, nodes.VariableShowStmt:
err = q.Query(ctx, stmt)
default:
err = q.Exec(ctx, stmt)
}
if err != nil {
return q.transport.Write(protocol.ErrorResponse(err))
}
}
return nil
}
func (q *query) Query(ctx context.Context, n nodes.Node) error {
rows, err := q.queryer.Query(ctx, n)
if err != nil {
return q.transport.Write(protocol.ErrorResponse(err))
}
// build columns from the provided columns list
cols := rows.Columns()
types := make([]string, len(cols))
rowsTypes, ok := rows.(driver.RowsColumnTypeDatabaseTypeName)
for i := 0; i < len(types) && ok; i++ {
types[i] = rowsTypes.ColumnTypeDatabaseTypeName(i)
}
err = q.transport.Write(protocol.RowDescription(cols, types))
if err != nil {
return err
}
count := 0
row := make([]driver.Value, len(cols))
strings := make([]string, len(cols))
for {
err = rows.Next(row)
if err == io.EOF {
break
} else if err != nil {
return q.transport.Write(protocol.ErrorResponse(err))
}
// convert the values to string
for i, v := range row {
strings[i] = fmt.Sprintf("%v", v)
}
err = q.transport.Write(protocol.DataRow(strings))
if err != nil {
return err
}
count++
}
tag := fmt.Sprintf("SELECT %d", count)
return q.transport.Write(protocol.CommandComplete(tag))
}
func (q *query) Exec(ctx context.Context, n nodes.Node) error {
res, err := q.execer.Exec(ctx, n)
if err != nil {
return q.transport.Write(protocol.ErrorResponse(err))
}
t, ok := res.(ResultTag)
if !ok {
t = &tagger{res, n}
}
tag, err := t.Tag()
if err != nil {
return q.transport.Write(protocol.ErrorResponse(err))
}
return q.transport.Write(protocol.CommandComplete(tag))
}
// QueryFromContext returns the sql string as saved in the given context
func QueryFromContext(ctx context.Context) string {
return ctx.Value(sqlCtxKey).(string)
}
// implements the CommandComplete tag according to the spec as described at the
// link below. When there's no suitable tag according to the spec, "UPDATE" is
// used instead.
// https://www.postgresql.org/docs/10/static/protocol-message-formats.html
type tagger struct {
driver.Result
Node nodes.Node
}
func (res *tagger) Tag() (tag string, err error) {
// allow commands to not specify number of rows affected
skipResults := false
switch res.Node.(type) {
case nodes.VariableSetStmt:
skipResults = true
kind := res.Node.(nodes.VariableSetStmt).Kind
switch kind {
case nodes.VAR_SET_VALUE, nodes.VAR_SET_CURRENT, nodes.VAR_SET_DEFAULT, nodes.VAR_SET_MULTI:
tag = "SET"
case nodes.VAR_RESET, nodes.VAR_RESET_ALL:
tag = "RESET"
default:
tag = "???"
}
case nodes.InsertStmt:
// oid in INSERT is not implemented; defaults to 0
tag = "INSERT 0"
case nodes.CreateTableAsStmt:
tag = "SELECT" // follows the spec
case nodes.DeleteStmt:
tag = "DELETE"
case nodes.FetchStmt:
tag = "FETCH"
case nodes.CopyStmt:
tag = "COPY"
case nodes.VacuumStmt:
skipResults = true
tag = "VACUUM"
case nodes.CreateRoleStmt:
skipResults = true
tag = "CREATE ROLE"
case nodes.ViewStmt:
skipResults = true
tag = "CREATE VIEW"
case nodes.CreateStmt:
skipResults = true
tag = "CREATE TABLE"
case nodes.UpdateStmt:
tag = "UPDATE"
default:
tag = "UPDATE"
}
if !skipResults {
affected, err := res.RowsAffected()
if err != nil {
return tag, err
}
tag = fmt.Sprintf("%s %d", tag, affected)
}
return tag, nil
}