Fix off-by-one error in deciding whether to match keys or prefixes

[angelamayxie]

-1 was causing us to try to match full keys when only a prefix was available. This lead to a panic when comparing tuples.

Panic exposed by dolthub/go-mysql-server#3099 because it caused us to pick lookup joins more frequently

[coffeegoddd]

@angelamayxie DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
94808d8	ok	5937457

version	total_tests
94808d8	5937457

correctness_percentage
100.0

[coffeegoddd]

@angelamayxie DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
1814476	ok	5937457

version	total_tests
1814476	5937457

correctness_percentage
100.0

[github-actions]

@coffeegoddd DOLT

test_name	detail	row_cnt	sorted	mysql_time	sql_mult	cli_mult
batching	LOAD DATA	10000	1	0.06	1.5
batching	batch sql	10000	1	0.08	1.5
batching	by line sql	10000	1	0.09	1.44
blob	1 blob	200000	1	0.9	4.12	4.86
blob	2 blobs	200000	1	0.89	4.56	5.09
blob	no blob	200000	1	0.96	2.55	2.88
col type	datetime	200000	1	0.8	2.69	3.05
col type	varchar	200000	1	0.82	3.12	3.35
config width	2 cols	200000	1	0.91	2.36	2.69
config width	32 cols	200000	1	1.9	2.59	2.9
config width	8 cols	200000	1	0.96	2.81	3.19
pk type	float	200000	1	2.04	1.06	1.32
pk type	int	200000	1	0.91	2.36	2.98
pk type	varchar	200000	1	1.49	1.83	1.97
row count	1.6mm	1600000	1	5.85	3.09	3.21
row count	400k	400000	1	1.49	2.95	3.19
row count	800k	800000	1	2.87	3.1	3.27
secondary index	four index	200000	1	3.69	1.46	1.42
secondary index	no secondary	200000	1	0.93	2.61	2.94
secondary index	one index	200000	1	1.18	2.6	2.75
secondary index	two index	200000	1	1.97	1.93	2
sorting	shuffled 1mm	1000000	0	5.55	2.9	2.99
sorting	sorted 1mm	1000000	1	5.65	2.86	2.86

[github-actions]

@coffeegoddd DOLT

name	detail	mean_mult
dolt_blame_basic	system table	1.17
dolt_blame_commit_filter	system table	2.87
dolt_commit_ancestors_commit_filter	system table	0.58
dolt_commits_commit_filter	system table	1.05
dolt_diff_log_join_from_commit	system table	2.73
dolt_diff_log_join_to_commit	system table	2.66
dolt_diff_table_from_commit_filter	system table	1.16
dolt_diff_table_to_commit_filter	system table	1.22
dolt_diffs_commit_filter	system table	1
dolt_history_commit_filter	system table	1.48
dolt_log_commit_filter	system table	1.11

[github-actions]

@coffeegoddd DOLT

name	add_cnt	delete_cnt	update_cnt	latency
adds_only	60000	0	0	1.14
adds_updates_deletes	60000	60000	60000	4.54
deletes_only	0	60000	0	2.43
updates_only	0	0	60000	3.08