Получение плана исполнения запроса и AST
Получить план запроса через YDB CLI можно с помощью команды explain:
ydb -p <profile_name> table query explain \
-q "SELECT season_id, episode_id, title
FROM episodes
WHERE series_id = 1
AND season_id > 1
ORDER BY season_id, episode_id
LIMIT 3"
Полученный результат:
Query Plan:
ResultSet
└──Limit (Limit: 3)
└──<Merge>
└──TopSort (Limit: 3, TopSortBy: )
└──Filter (Predicate: Exist(item.season_id) And Exist(item.series_id))
└──TablePointLookup (ReadRange: [series_id (1), season_id (1, +∞), episode_id (-∞, +∞)], ReadColumns: [episode_id, season_id, title, series_id], Table: episodes)
Tables: [episodes]
Дополнительно к плану запроса вы можете получить AST (абстрактное синтаксическое дерево).
Раздел AST содержит представление на внутреннем языке miniKQL.
Для получения AST необходимо вызвать explain с флагом --ast:
ydb -p <profile_name> table query explain \
-q "SELECT season_id, episode_id, title
FROM episodes
WHERE series_id = 1
AND season_id > 1
ORDER BY season_id, episode_id
LIMIT 3" --ast
Полученный AST:
Query AST:
(
(let $1 (KqpTable '"episodes" '"72075186224045943:83859" '"" '1))
(let $2 '('"episode_id" '"season_id" '"title" '"series_id"))
(let $3 (Uint64 '1))
(let $4 (KqpRowsSourceSettings $1 $2 '() '((KqlKeyExc $3 $3) (KqlKeyInc $3))))
(let $5 (Uint64 '"3"))
(let $6 (DqPhyStage '((DqSource (DataSource '"KqpReadRangesSource") $4)) (lambda '($12) (block '(
(let $13 (Bool 'true))
(return (FromFlow (TopSort (OrderedMap (OrderedFilter (ToFlow $12) (lambda '($14) (And (Exists (Member $14 '"season_id")) (Exists (Member $14 '"series_id"))))) (lambda '($15) (AsStruct '('"episode_id" (Member $15 '"episode_id")) '('"season_id" (Member $15 '"season_id")) '('"title" (Member $15 '"title"))))) $5 '($13 $13) (lambda '($16) '((Member $16 '"season_id") (Member $16 '"episode_id"))))))
))) '('('"_logical_id" '842) '('"_id" '"14388682-e03b28dd-60f91f84-d7cd002f"))))
(let $7 (DqCnMerge (TDqOutput $6 '0) '('('"season_id" '"Asc") '('"episode_id" '"Asc"))))
(let $8 (DqPhyStage '($7) (lambda '($17) (FromFlow (Take (ToFlow $17) $5))) '('('"_logical_id" '855) '('"_id" '"295c0459-34d4b026-b467e71f-35402430"))))
(let $9 '('"season_id" '"episode_id" '"title"))
(let $10 (DqCnResult (TDqOutput $8 '0) $9))
(let $11 (OptionalType (DataType 'Uint64)))
(return (KqpPhysicalQuery '((KqpPhysicalTx '($6 $8) '($10) '() '('('"type" '"data")))) '((KqpTxResultBinding (ListType (StructType '('"episode_id" $11) '('"season_id" $11) '('"title" (OptionalType (DataType 'String))))) '0 '0)) '('('"type" '"data_query"))))
)