Match index degeneration

[czpmango]

Currently, Indexes of match statements have the following degradation related issues:

1. FullTagScan cannot be degraded if the index is not selected

(czp@nebula) [nba]> show tag indexes
+---------------------+----------+----------+
| Index Name          | By Tag   | Columns  |
+---------------------+----------+----------+
| "player_name_index" | "player" | ["name"] |
+---------------------+----------+----------+
| "team_name_index"   | "team"   | ["name"] |
+---------------------+----------+----------+
Got 2 rows (time spent 2985/3978 us)

Query 1:
match (v:player)
return v

Query 2:
match (v:player)
where v.age>40
return v

Query 1(expected): FullTagScan
Query 2(unexpected): The execution result is an error. The expectation is to degenerate to FullTagScan when there is no index on player(age).

2. A low-priority index cannot be degraded if a high-priority index is not selected

(czp@nebula) [nba]> show tag indexes
+---------------------+----------+----------+
| Index Name          | By Tag   | Columns  |
+---------------------+----------+----------+
| "player_name_index" | "player" | ["name"] |
+---------------------+----------+----------+
| "team_name_index"   | "team"   | ["name"] |
+---------------------+----------+----------+
Got 2 rows (time spent 3728/4894 us)

Query 3:
match (v:player)
where v.name=="Tim"
return v

Query 4:
match (v:player)
where v.name=="Tim" and v.age==40
return v

Query 3(expected): PrefixIndex(player.name)
Query 4(unexpected): The execution result is an error. The expectation is to degenerate to PrefixIndex(player.name) when there is no index on player(name,age).

3. The composite index was not selected as expected

(czp@nebula) [nba]> show tag indexes
+----------------------+----------+-----------------+
| Index Name           | By Tag   | Columns         |
+----------------------+----------+-----------------+
| "player_age_index"   | "player" | ["age"]         |
+----------------------+----------+-----------------+
| "player_multi_index" | "player" | ["name", "age"] |
+----------------------+----------+-----------------+
| "player_name_index"  | "player" | ["name"]        |
+----------------------+----------+-----------------+
| "team_name_index"    | "team"   | ["name"]        |
+----------------------+----------+-----------------+
Got 4 rows (time spent 3328/4334 us)

Query 5:
match (v:player)--(n:team)
where v.name=="Tim" and v.age>40
return v

Query 6:
match (v:player)--(n:team)
where v.name=="Tim" and v.age>40 and v.name=="Tim"
return v

Query 5(expected): CompositeIndex(name,age)
Query 6(unexpected): The execution result is an error. The expected index is CompositeIndex(name,age)