Expose Badger Compression Level option in Bulk Loader

[jarifibrahim]

This PR exposes badger's CompressionLevel option in bulk loader.

Fixes #4439

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This change is 

[danielmai]

Reviewed 3 of 3 files at r2.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @jarifibrahim and @manishrjain)

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dgraph/cmd/bulk/reduce.go, line 152 at r2 (raw file):

	opt.ZSTDCompressionLevel = r.state.opt.BadgerCompressionLevel
	if r.state.opt.BadgerCompressionLevel < 1 {
		opt.ZSTDCompressionLevel = 1

We should throw an error if the compression level is invalid.

0 might be a valid value (to disable compression).

[jarifibrahim]

Reviewable status: 2 of 3 files reviewed, 1 unresolved discussion (waiting on @danielmai and @manishrjain)

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dgraph/cmd/bulk/reduce.go, line 152 at r2 (raw file):

Previously, danielmai (Daniel Mai) wrote…

We should throw an error if the compression level is invalid.

0 might be a valid value (to disable compression).

0 should not be used to disable the compression. We have a separate option to set the compression algorithm and disable it

https://github.com/dgraph-io/badger/blob/master/options.go#L126

[danielmai]

Can we change this PR so it's just for the compression flag? There's actually no need for the table/vlog options in bulk loader.

Reviewable status: 2 of 3 files reviewed, 1 unresolved discussion (waiting on @danielmai and @manishrjain)

[jarifibrahim]

Yes. I've removed the table and vlog loading mode option. 👍

Reviewable status: 0 of 3 files reviewed, 1 unresolved discussion (waiting on @danielmai and @manishrjain)

[danielmai]

One comment, and then . Do update the PR title and description. This closes #4439.

Reviewed 3 of 3 files at r3.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @danielmai, @jarifibrahim, and @manishrjain)

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dgraph/cmd/bulk/loader.go, line 73 at r3 (raw file):

	// BadgerKeyFile is the file containing the key used for encryption. Enterprise only feature.
	BadgerKeyFile string
	// Badger is the compression level to use while writing to badger.

BadgerCompressionLevel is

[martinmr]

Reviewed 3 of 3 files at r3.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @danielmai, @jarifibrahim, and @manishrjain)