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alternateclient.go
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alternateclient.go
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// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.
package postgreskv
import (
"context"
"database/sql"
"github.com/zeebo/errs"
"storj.io/storj/storage"
)
const (
alternateSQLSetup = `
CREATE OR REPLACE FUNCTION local_path (fullpath BYTEA, prefix BYTEA, delimiter BYTEA)
RETURNS BYTEA AS $$
DECLARE
relative BYTEA;
pos INTEGER;
BEGIN
relative := substring(fullpath FROM (octet_length(prefix)+1));
pos := position(delimiter IN relative);
IF pos = 0 THEN
RETURN relative;
END IF;
RETURN substring(relative FOR pos);
END;
$$ LANGUAGE 'plpgsql'
IMMUTABLE STRICT;
`
alternateSQLTeardown = `
DROP FUNCTION local_path(BYTEA, BYTEA, BYTEA);
`
alternateForwardQuery = `
SELECT DISTINCT
$2::BYTEA || x.localpath AS p,
first_value(x.metadata) OVER (PARTITION BY x.localpath ORDER BY x.fullpath) AS m
FROM (
SELECT
pd.fullpath,
local_path(pd.fullpath, $2::BYTEA, set_byte(' '::BYTEA, 0, b.delim)) AS localpath,
pd.metadata
FROM
pathdata pd,
buckets b
WHERE
b.bucketname = $1::BYTEA
AND pd.bucket = b.bucketname
AND pd.fullpath >= $2::BYTEA
AND ($2::BYTEA = ''::BYTEA OR pd.fullpath < bytea_increment($2::BYTEA))
AND pd.fullpath >= $3::BYTEA
) x
ORDER BY p
LIMIT $4
`
alternateReverseQuery = `
SELECT DISTINCT
$2::BYTEA || x.localpath AS p,
first_value(x.metadata) OVER (PARTITION BY x.localpath ORDER BY x.fullpath) AS m
FROM (
SELECT
pd.fullpath,
local_path(pd.fullpath, $2::BYTEA, set_byte(' '::BYTEA, 0, b.delim)) AS localpath,
pd.metadata
FROM
pathdata pd,
buckets b
WHERE
b.bucketname = $1::BYTEA
AND pd.bucket = b.bucketname
AND pd.fullpath >= $2::BYTEA
AND ($2::BYTEA = ''::BYTEA OR pd.fullpath < bytea_increment($2::BYTEA))
AND ($3::BYTEA = ''::BYTEA OR pd.fullpath <= $3::BYTEA)
) x
ORDER BY p DESC
LIMIT $4
`
)
// AlternateClient is the entrypoint into an alternate postgreskv data store
type AlternateClient struct {
*Client
}
// AltNew instantiates a new postgreskv AlternateClient given db URL
func AltNew(dbURL string) (*AlternateClient, error) {
client, err := New(dbURL)
if err != nil {
return nil, err
}
_, err = client.pgConn.Exec(alternateSQLSetup)
if err != nil {
return nil, errs.Combine(err, client.Close())
}
return &AlternateClient{Client: client}, nil
}
// Close closes an AlternateClient and frees its resources.
func (altClient *AlternateClient) Close() error {
_, err := altClient.pgConn.Exec(alternateSQLTeardown)
return errs.Combine(err, altClient.Client.Close())
}
type alternateOrderedPostgresIterator struct {
*orderedPostgresIterator
}
func (opi *alternateOrderedPostgresIterator) doNextQuery(ctx context.Context) (_ *sql.Rows, err error) {
defer mon.Task()(&ctx)(&err)
if opi.opts.Recurse {
return opi.orderedPostgresIterator.doNextQuery(ctx)
}
start := opi.lastKeySeen
if start == nil {
start = opi.opts.First
}
var query string
if opi.opts.Reverse {
query = alternateReverseQuery
} else {
query = alternateForwardQuery
}
return opi.client.pgConn.Query(query, []byte(opi.bucket), []byte(opi.opts.Prefix), []byte(start), opi.batchSize+1)
}
func newAlternateOrderedPostgresIterator(ctx context.Context, altClient *AlternateClient, opts storage.IterateOptions, batchSize int) (_ *alternateOrderedPostgresIterator, err error) {
defer mon.Task()(&ctx)(&err)
if opts.Prefix == nil {
opts.Prefix = storage.Key("")
}
if opts.First == nil {
opts.First = storage.Key("")
}
opi1 := &orderedPostgresIterator{
client: altClient.Client,
opts: &opts,
bucket: storage.Key(defaultBucket),
delimiter: byte('/'),
batchSize: batchSize,
curIndex: 0,
}
opi := &alternateOrderedPostgresIterator{orderedPostgresIterator: opi1}
opi.nextQuery = opi.doNextQuery
newRows, err := opi.nextQuery(ctx)
if err != nil {
return nil, err
}
opi.curRows = newRows
return opi, nil
}
// Iterate iterates over items based on opts
func (altClient *AlternateClient) Iterate(ctx context.Context, opts storage.IterateOptions, fn func(context.Context, storage.Iterator) error) (err error) {
defer mon.Task()(&ctx)(&err)
opi, err := newAlternateOrderedPostgresIterator(ctx, altClient, opts, defaultBatchSize)
if err != nil {
return err
}
defer func() {
err = errs.Combine(err, opi.Close())
}()
return fn(ctx, opi)
}