115 lines
2.5 KiB
Go
115 lines
2.5 KiB
Go
package query
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import (
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"fmt"
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"github.com/cosmos/cosmos-sdk/store/types"
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)
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// FilteredPaginate does pagination of all the results in the PrefixStore based on the
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// provided PageRequest. onResult should be used to do actual unmarshaling and filter the results.
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// If key is provided, the pagination uses the optimized querying.
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// If offset is used, the pagination uses lazy filtering i.e., searches through all the records.
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// The accumulate parameter represents if the response is valid based on the offset given.
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// It will be false for the results (filtered) < offset and true for `offset > accumulate <= end`.
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// When accumulate is set to true the current result should be appended to the result set returned
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// to the client.
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func FilteredPaginate(
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prefixStore types.KVStore,
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pageRequest *PageRequest,
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onResult func(key []byte, value []byte, accumulate bool) (bool, error),
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) (*PageResponse, error) {
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// if the PageRequest is nil, use default PageRequest
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if pageRequest == nil {
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pageRequest = &PageRequest{}
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}
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offset := pageRequest.Offset
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key := pageRequest.Key
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limit := pageRequest.Limit
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countTotal := pageRequest.CountTotal
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if offset > 0 && key != nil {
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return nil, fmt.Errorf("invalid request, either offset or key is expected, got both")
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}
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if limit == 0 {
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limit = defaultLimit
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// count total results when the limit is zero/not supplied
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countTotal = true
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}
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if len(key) != 0 {
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iterator := prefixStore.Iterator(key, nil)
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defer iterator.Close()
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var numHits uint64
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var nextKey []byte
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for ; iterator.Valid(); iterator.Next() {
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if numHits == limit {
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nextKey = iterator.Key()
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break
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}
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if iterator.Error() != nil {
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return nil, iterator.Error()
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}
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hit, err := onResult(iterator.Key(), iterator.Value(), true)
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if err != nil {
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return nil, err
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}
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if hit {
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numHits++
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}
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}
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return &PageResponse{
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NextKey: nextKey,
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}, nil
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}
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iterator := prefixStore.Iterator(nil, nil)
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defer iterator.Close()
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end := offset + limit
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var numHits uint64
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var nextKey []byte
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for ; iterator.Valid(); iterator.Next() {
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if iterator.Error() != nil {
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return nil, iterator.Error()
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}
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accumulate := numHits >= offset && numHits < end
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hit, err := onResult(iterator.Key(), iterator.Value(), accumulate)
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if err != nil {
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return nil, err
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}
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if hit {
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numHits++
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}
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if numHits == end+1 {
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nextKey = iterator.Key()
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if !countTotal {
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break
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}
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}
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}
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res := &PageResponse{NextKey: nextKey}
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if countTotal {
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res.Total = numHits
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}
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return res, nil
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}
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