Query: TPC prune unused concrete tables and columns #27993
Conversation
| SELECT [k].[Species], [k].[CountryId], [k].[Name], [k].[EagleId], [k].[IsFlightless], NULL AS [Group], [k].[FoundOn], N'Kiwi' AS [Discriminator] | ||
| FROM [Kiwi] AS [k] | ||
| ) AS [t] | ||
| WHERE [t].[CountryId] = 1 AND [t].[Discriminator] = N'Kiwi'"); |
There was a problem hiding this comment.
Table pruning example
| @@ -77,10 +74,10 @@ public override async Task Can_use_is_kiwi_in_projection(bool async) | |||
| ELSE CAST(0 AS bit) | |||
| END | |||
| FROM ( | |||
| SELECT [e].[Species], [e].[CountryId], [e].[Name], [e].[EagleId], [e].[IsFlightless], [e].[Group], NULL AS [FoundOn], N'Eagle' AS [Discriminator] | |||
There was a problem hiding this comment.
Column pruning example
| @@ -1350,6 +1328,59 @@ public void ApplyPredicate(SqlExpression sqlExpression) | |||
| sqlExpression = PushdownIntoSubqueryInternal().Remap(sqlExpression); | |||
| } | |||
|
|
|||
| if ((sqlExpression is SqlBinaryExpression { OperatorType: ExpressionType.Equal } | |||
| || sqlExpression is InExpression { Subquery: null, IsNegated: false }) | |||
| && _groupBy.Count == 0) | |||
There was a problem hiding this comment.
This is the only condition in Select before swallowing predicate and pruning table.
@maumar to review.
Limit/Offset are deal with above itself. If they are present, pushdown will happen and we won't find the Tpc table anyway.
Other predicates are fine since they do AND so it will work.
GroupBy is not allowed, also implies no HAVING
DISTINCT is ok because it applies after filtering.
Other tables in SelectExpression doesn't affect the base as predicate applies to whole result. For TPC in joined table, the predicate would be specified before the join (that scenario works already). If predicate is applied to result of join then it becomes complicated to track down TPC because it would be inside subquery in joined table. User can always do filtering before.
Ordering is applied after filtering so that is also fine (unless limit/offset which is already handled).
Do we need anymore condition (certain thing on Select) which makes this optimization incorrect?
There was a problem hiding this comment.
could be useful to add this comment in the code
- Add TpcTablesExpression which holds all union all tables so we can prune unused subqueries - Also allow pruning of unused column inside each subquery - Assign unique aliases in inner subqueries across whole SelectExpression - Apply predicate on discriminator column directly to subqueries by removing unnecessary subqueries Resolves #27967 Resolves #27957
| UNION ALL | ||
| SELECT [o0].[Nickname], [o0].[SquadId], [o0].[AssignedCityName], [o0].[CityOfBirthName], [o0].[FullName], [o0].[HasSoulPatch], [o0].[LeaderNickname], [o0].[LeaderSquadId], [o0].[Rank], N'Officer' AS [Discriminator] | ||
| FROM [Officers] AS [o0] | ||
| SELECT [t2].[Nickname], [t2].[Rank], [t2].[SquadId], [t2].[FullName], [t2].[LeaderNickname], [t2].[LeaderSquadId] |
There was a problem hiding this comment.
we could lift this case also
| FROM [Officers] AS [o4] | ||
| ) AS [t7] ON [s].[Id] = [t7].[SquadId] | ||
| SELECT [t10].[Nickname], [t10].[HasSoulPatch], [t10].[SquadId] | ||
| FROM ( |
| UNION ALL | ||
| SELECT [o0].[Nickname], [o0].[SquadId], [o0].[AssignedCityName], [o0].[CityOfBirthName], [o0].[FullName], [o0].[HasSoulPatch], [o0].[LeaderNickname], [o0].[LeaderSquadId], [o0].[Rank], N'Officer' AS [Discriminator] | ||
| FROM [Officers] AS [o0] | ||
| SELECT [t3].[FullName], [t3].[Nickname], [t3].[SquadId], [t3].[LeaderNickname], [t3].[LeaderSquadId] |
Resolves #27967
Resolves #27957