Fix transaction too big issue in restore

[jarifibrahim]

When restore happens, we bunch entries together and perform batch
write. The existing implementation would batch 1000 entries. The batch
of 1000 entries can overflow the transactional limits in certain
circumstances (eg: when table size is too small). This commit fixes the
issue. We flush the entries once the batch reaches its max capacity

Fixes #820

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This change is 

[jarifibrahim]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @ashish-goswami and @manishrjain)

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backup.go, line 186 at r1 (raw file):

Previously, ashish-goswami (Ashish Goswami) wrote…

We should not do this as this will modify entries slice already passed to db.batchSetAsync.

Nice catch. Thanks! Fixed it.

[ashish-goswami]

Reviewable status: 0 of 1 files reviewed, 2 unresolved discussions (waiting on @ashish-goswami, @jarifibrahim, and @manishrjain)

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backup.go, line 135 at r2 (raw file):

	throttle    *y.Throttle
	entries     []*Entry
	entriesSize int64

uint64??

[jarifibrahim]

Reviewable status: 0 of 1 files reviewed, 2 unresolved discussions (waiting on @ashish-goswami and @manishrjain)

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backup.go, line 135 at r2 (raw file):

Previously, ashish-goswami (Ashish Goswami) wrote…

uint64??

opt.maxBatch size is of int64 type. I've used int64 here so that we don't have to cast it before comparing it to opt.maxBatch size.

[poonai]

Reviewable status: 0 of 1 files reviewed, 3 unresolved discussions (waiting on @ashish-goswami, @jarifibrahim, and @manishrjain)

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backup.go, line 167 at r2 (raw file):

	if int64(len(l.entries))+1 >= l.db.opt.maxBatchCount ||
		l.entriesSize+estimatedSize >= l.db.opt.maxBatchSize {
		if err := l.send(); err != nil {

nitpick :P just return it

[manishrjain]

Reviewed 1 of 1 files at r2.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @ashish-goswami and @jarifibrahim)

[jarifibrahim]

Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @ashish-goswami and @Sch00lb0y)

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backup.go, line 167 at r2 (raw file):

Previously, sch00lb0y (balaji) wrote…

nitpick :P just return it

@Sch00lb0y I can't return it from here. We want to return only if there's an error, otherwise, we want to continue.