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transactions.go
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transactions.go
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package query
import (
"bytes"
"context"
"encoding/json"
"fmt"
"math"
"strconv"
"chain/core/query/filter"
"chain/errors"
)
var (
ErrBadAfter = errors.New("malformed pagination parameter after")
ErrParameterCountMismatch = errors.New("wrong number of parameters to query")
)
type TxAfter struct {
// FromBlockHeight and FromPosition uniquely identify the last transaction returned
// by a list-transactions query.
//
// If list-transactions is called with a time range instead of an `after`, these fields
// are populated with the position of the transaction at the start of the time range.
FromBlockHeight uint64 // exclusive
FromPosition uint32 // exclusive
// StopBlockHeight identifies the last block that should be included in a transaction
// list. It is used when list-transactions is called with a time range instead
// of an `after`.
StopBlockHeight uint64 // inclusive
}
func (after TxAfter) String() string {
return fmt.Sprintf("%d:%d-%d", after.FromBlockHeight, after.FromPosition, after.StopBlockHeight)
}
func DecodeTxAfter(str string) (c TxAfter, err error) {
var from, pos, stop uint64
_, err = fmt.Sscanf(str, "%d:%d-%d", &from, &pos, &stop)
if err != nil {
return c, errors.Wrap(ErrBadAfter, err.Error())
}
if from > math.MaxInt64 ||
pos > math.MaxUint32 ||
stop > math.MaxInt64 {
return c, errors.Wrap(ErrBadAfter)
}
return TxAfter{FromBlockHeight: from, FromPosition: uint32(pos), StopBlockHeight: stop}, nil
}
// LookupTxAfter looks up the transaction `after` for the provided time range.
func (ind *Indexer) LookupTxAfter(ctx context.Context, begin, end uint64) (TxAfter, error) {
const q = `
SELECT COALESCE(MAX(height), 0), COALESCE(MIN(height), 0) FROM query_blocks
WHERE timestamp >= $1 AND timestamp <= $2
`
var from, stop uint64
err := ind.db.QueryRow(ctx, q, begin, end).Scan(&from, &stop)
if err != nil {
return TxAfter{}, errors.Wrap(err, "querying `query_blocks`")
}
return TxAfter{
FromBlockHeight: from,
FromPosition: math.MaxInt32, // TODO(tessr): Support reversing direction.
StopBlockHeight: stop,
}, nil
}
// Transactions queries the blockchain for transactions matching the
// filter predicate `p`.
func (ind *Indexer) Transactions(ctx context.Context, p filter.Predicate, vals []interface{}, after TxAfter, limit int, asc bool) ([]interface{}, *TxAfter, error) {
if len(vals) != p.Parameters {
return nil, nil, ErrParameterCountMismatch
}
expr, err := filter.AsSQL(p, "data", vals)
if err != nil {
return nil, nil, errors.Wrap(err, "converting to SQL")
}
queryStr, queryArgs := constructTransactionsQuery(expr, after, asc, limit)
if asc {
return ind.waitForAndFetchTransactions(ctx, queryStr, queryArgs, after, limit)
}
return ind.fetchTransactions(ctx, queryStr, queryArgs, after, limit)
}
// If asc is true, the transactions will be returned from "in front" of the `after`
// param (e.g., the oldest transaction immediately after the `after` param,
// followed by the second oldest, etc) in ascending order.
func constructTransactionsQuery(expr filter.SQLExpr, after TxAfter, asc bool, limit int) (string, []interface{}) {
var buf bytes.Buffer
var vals []interface{}
buf.WriteString("SELECT block_height, tx_pos, data FROM annotated_txs")
buf.WriteString(" WHERE ")
// add filter conditions
if len(expr.SQL) > 0 {
vals = append(vals, expr.Values...)
buf.WriteString(expr.SQL)
buf.WriteString(" AND ")
}
if asc {
// add time range & after conditions
buf.WriteString(fmt.Sprintf("(block_height, tx_pos) > ($%d, $%d) AND ", len(vals)+1, len(vals)+2))
buf.WriteString(fmt.Sprintf("block_height <= $%d ", len(vals)+3))
vals = append(vals, after.FromBlockHeight, after.FromPosition, after.StopBlockHeight)
buf.WriteString("ORDER BY block_height ASC, tx_pos ASC ")
} else {
// add time range & after conditions
buf.WriteString(fmt.Sprintf("(block_height, tx_pos) < ($%d, $%d) AND ", len(vals)+1, len(vals)+2))
buf.WriteString(fmt.Sprintf("block_height >= $%d ", len(vals)+3))
vals = append(vals, after.FromBlockHeight, after.FromPosition, after.StopBlockHeight)
buf.WriteString("ORDER BY block_height DESC, tx_pos DESC ")
}
buf.WriteString("LIMIT " + strconv.Itoa(limit))
return buf.String(), vals
}
func (ind *Indexer) fetchTransactions(ctx context.Context, queryStr string, queryArgs []interface{}, after TxAfter, limit int) ([]interface{}, *TxAfter, error) {
rows, err := ind.db.Query(ctx, queryStr, queryArgs...)
if err != nil {
return nil, nil, errors.Wrap(err, "executing txn query")
}
defer rows.Close()
txns := make([]interface{}, 0, limit)
for rows.Next() {
var data []byte
err := rows.Scan(&after.FromBlockHeight, &after.FromPosition, &data)
if err != nil {
return nil, nil, errors.Wrap(err, "scanning transaction row")
}
txns = append(txns, (*json.RawMessage)(&data))
}
err = rows.Err()
if err != nil {
return nil, nil, errors.Wrap(err)
}
return txns, &after, nil
}
type fetchResp struct {
txns []interface{}
after *TxAfter
err error
}
func (ind *Indexer) waitForAndFetchTransactions(ctx context.Context, queryStr string, queryArgs []interface{}, after TxAfter, limit int) ([]interface{}, *TxAfter, error) {
resp := make(chan fetchResp, 1)
go func() {
var (
txs []interface{}
aft *TxAfter
err error
)
for h := ind.c.Height(); len(txs) == 0; h++ {
<-ind.pinStore.Pin(TxPinName).WaitForHeight(h)
if err != nil {
resp <- fetchResp{nil, nil, err}
return
}
txs, aft, err = ind.fetchTransactions(ctx, queryStr, queryArgs, after, limit)
if err != nil {
resp <- fetchResp{nil, nil, err}
return
}
if len(txs) > 0 {
resp <- fetchResp{txs, aft, nil}
return
}
}
}()
select {
case <-ctx.Done():
return nil, nil, ctx.Err()
case r := <-resp:
return r.txns, r.after, r.err
}
}