Vdiff formatting improvements

[rafael]

Description

The following change improves how diffs are reported to users. In paticular it adds the following:

• Adds sample rows to the diff report. This allows us to show the diff in a way that is more structured and with better formatting.
• Adds a debug option that will add a Query to the diff report. This query can then later be used to check the actual vitess shards and perform further debugging.
• Adds a onlyPks option to only report this information in the diffs. This is useful for cases where the data could have PII information.
• Last but not least, all this info is used to provide a more comprehensive report at the end of the run.

These are the kind of reports that now can be generated with these changes:

vtctl VDiff  -debug test.copy_rafael_test
Summary for table test_rafael_materialized:
	ProcessedRows: 39055
	MatchingRows: 39053
	MismatchedRows: 0
	ExtraRowsSource: 0
	ExtraRowsTarget: 2
	Sample extra row in target 0:
		Row:
			 `column`: null (NULL_TYPE)
			 `data`: "3232" (BLOB)
			 id: 23232 (INT32)
			 id1: 1 (INT32)
			 id2: "1" (VARCHAR)
			 id3: 0.5 (FLOAT64)
			 weight_string(`column`): null (NULL_TYPE)
			 weight_string(id2): "\x001" (VARBINARY)
		DebugQuery: select id, `data`, id1, id2, id3, `column`, weight_string(id2), weight_string(`column`) from test_rafael_materialized where id=23232 AND id1=1 AND id2='1' AND id3=0.5;
	Sample extra row in target 1:
		Row:
			 `column`: null (NULL_TYPE)
			 `data`: "33123123123131312323...[TRUNCATED]" (BLOB)
			 id: 232232 (INT32)
			 id1: 1 (INT32)
			 id2: "1" (VARCHAR)
			 id3: 0.5 (FLOAT64)
			 weight_string(`column`): null (NULL_TYPE)
			 weight_string(id2): "\x001" (VARBINARY)
		DebugQuery: select id, `data`, id1, id2, id3, `column`, weight_string(id2), weight_string(`column`) from test_rafael_materialized where id=232232 AND id1=1 AND id2='1' AND id3=0.5;

or

vtctl VDiff  test.copy_rafael_test -only_pks

Summary for table test_rafael_materialized:
	ProcessedRows: 39055
	MatchingRows: 39053
	MismatchedRows: 0
	ExtraRowsSource: 0
	ExtraRowsTarget: 2
	Sample extra row in target 0:
		Row:
			 id: 23232 (INT32)
			 id1: 1 (INT32)
			 id2: "1" (VARCHAR)
			 id3: 0.5 (FLOAT64)
	Sample extra row in target 1:
		Row:
			 id: 232232 (INT32)
			 id1: 1 (INT32)
			 id2: "1" (VARCHAR)
			 id3: 0.5 (FLOAT64)

Checklist

• Tests were added or are not required
• Documentation was added or is not required

[rohit-nayak-ps]

nice! lgtm

[rohit-nayak-ps]

@rafael , can you also create a PR to update the docs for vdiff at https://vitess.io/docs/reference/vreplication/vdiff/ (https://github.com/vitessio/website) with the new options and the sample? Thx

[rafael]

@rafael , can you also create a PR to update the docs for vdiff at https://vitess.io/docs/reference/vreplication/vdiff/ (https://github.com/vitessio/website) with the new options and the sample? Thx

Yes, will do!