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refactor: correlated subquery for o2m query

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Improves the query costs a bit as shown in the tests and reduces code.
This commit is contained in:
steve-chavez
2022-08-06 21:42:53 -05:00
committed by Steve Chavez
parent c050b61db8
commit 3648986aa8
2 changed files with 31 additions and 38 deletions
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src/PostgREST/Query/QueryBuilder.hs
+24 -31
View File
@@ -38,7 +38,7 @@ import Protolude
readRequestToQuery :: ReadRequest -> SQL.Snippet
readRequestToQuery (Node (Select colSelects mainQi tblAlias implJoins logicForest joinConditions_ ordts range, _) forest) =
"SELECT " <>
intercalateSnippet ", " ((pgFmtSelectItem qi <$> colSelects) ++ selects) <>
intercalateSnippet ", " ((pgFmtSelectItem qi <$> colSelects) ++ selects) <> " " <>
"FROM " <> SQL.sql (BS.intercalate ", " (tabl : implJs)) <> " " <>
intercalateSnippet " " joins <> " " <>
(if null logicForest && null joinConditions_
@@ -50,38 +50,31 @@ readRequestToQuery (Node (Select colSelects mainQi tblAlias implJoins logicFores
implJs = fromQi <$> implJoins
tabl = fromQi mainQi <> maybe mempty (\a -> " AS " <> pgFmtIdent a) tblAlias
qi = maybe mainQi (QualifiedIdentifier mempty) tblAlias
(joins, selects) = foldr getJoinsSelects ([],[]) forest
(selects, joins) = foldr getSelectsJoins ([],[]) forest
getJoinsSelects :: ReadRequest -> ([SQL.Snippet], [SQL.Snippet]) -> ([SQL.Snippet], [SQL.Snippet])
getJoinsSelects rr@(Node (_, (name, Just Relationship{relCardinality=card,relTable=QualifiedIdentifier{qiName=table}}, alias, _, joinType, _)) _) (joins,selects) =
let subquery = readRequestToQuery rr in
case card of
M2O _ _ ->
let aliasOrName = fromMaybe name alias
localTableName = pgFmtIdent $ table <> "_" <> aliasOrName
sel = SQL.sql ("row_to_json(" <> localTableName <> ".*) AS " <> pgFmtIdent aliasOrName)
joi = (if joinType == Just JTInner then " INNER" else " LEFT")
<> " JOIN LATERAL( " <> subquery <> " ) AS " <> SQL.sql localTableName <> " ON TRUE " in
(joi:joins,sel:selects)
_ -> case joinType of
Just JTInner ->
let aliasOrName = fromMaybe name alias
locTblName = table <> "_" <> aliasOrName
localTableName = pgFmtIdent locTblName
internalTableName = pgFmtIdent $ "_" <> locTblName
sel = SQL.sql $ localTableName <> "." <> internalTableName <> " AS " <> pgFmtIdent aliasOrName
joi = "INNER JOIN LATERAL(" <>
"SELECT json_agg(" <> SQL.sql internalTableName <> ") AS " <> SQL.sql internalTableName <>
"FROM (" <> subquery <> " ) AS " <> SQL.sql internalTableName <>
") AS " <> SQL.sql localTableName <> " ON " <> SQL.sql localTableName <> "IS NOT NULL" in
(joi:joins,sel:selects)
getSelectsJoins :: ReadRequest -> ([SQL.Snippet], [SQL.Snippet]) -> ([SQL.Snippet], [SQL.Snippet])
getSelectsJoins rr@(Node (_, (name, Just Relationship{relCardinality=card,relTable=QualifiedIdentifier{qiName=table}}, alias, _, joinType, _)) _) (selects,joins) =
let
subquery = readRequestToQuery rr
aliasOrName = fromMaybe name alias
locTblName = table <> "_" <> aliasOrName
localTableName = pgFmtIdent locTblName
internalTableName = pgFmtIdent $ "_" <> locTblName
correlatedSubquery sub al cond =
(if joinType == Just JTInner then "INNER" else "LEFT") <> " JOIN LATERAL ( " <> sub <> " ) AS " <> SQL.sql al <> " ON " <> cond
(sel, joi) = case card of
M2O _ _ ->
( SQL.sql ("row_to_json(" <> localTableName <> ".*) AS " <> pgFmtIdent aliasOrName)
, correlatedSubquery subquery localTableName "TRUE")
_ ->
let sel = "COALESCE (("
<> "SELECT json_agg(" <> SQL.sql (pgFmtIdent table) <> ".*) "
<> "FROM (" <> subquery <> ") " <> SQL.sql (pgFmtIdent table) <> " "
<> "), '[]') AS " <> SQL.sql (pgFmtIdent (fromMaybe name alias)) in
(joins,sel:selects)
getJoinsSelects (Node (_, (_, Nothing, _, _, _, _)) _) _ = ([], [])
( SQL.sql $ "COALESCE( " <> localTableName <> "." <> internalTableName <> ", '[]') AS " <> pgFmtIdent aliasOrName
, correlatedSubquery (
"SELECT json_agg(" <> SQL.sql internalTableName <> ") AS " <> SQL.sql internalTableName <>
"FROM (" <> subquery <> " ) AS " <> SQL.sql internalTableName
) localTableName $ if joinType == Just JTInner then SQL.sql localTableName <> " IS NOT NULL" else "TRUE")
in
(sel:selects, joi:joins)
getSelectsJoins (Node (_, (_, Nothing, _, _, _, _)) _) _ = ([], [])
mutateRequestToQuery :: MutateRequest -> SQL.Snippet
mutateRequestToQuery (Insert mainQi iCols body onConflct putConditions returnings) =
test/spec/Feature/Query/PlanSpec.hs
+7 -7
View File
@@ -14,8 +14,8 @@ import Test.Hspec hiding (pendingWith)
import Test.Hspec.Wai
import Test.Hspec.Wai.JSON
import PostgREST.Config.PgVersion (PgVersion, pgVersion120,
pgVersion130, pgVersion100)
import PostgREST.Config.PgVersion (PgVersion, pgVersion100,
pgVersion120, pgVersion130)
import Protolude hiding (get)
import SpecHelper
@@ -274,8 +274,8 @@ spec actualPgVersion = do
let totalCost = simpleBody r ^? nth 0 . key "Plan" . key "Total Cost"
liftIO $ totalCost `shouldBe`
if actualPgVersion > pgVersion120
then Just [aesonQQ|58.26|]
else Just [aesonQQ|33.25|]
then Just [aesonQQ|33.25|]
else Just [aesonQQ|33.27|]
it "a many to one doesn't surpass a threshold" $ do
r <- request methodGet "/projects?select=*,clients(*)&id=eq.1"
@@ -293,9 +293,9 @@ spec actualPgVersion = do
let totalCost = simpleBody r ^? nth 0 . key "Plan" . key "Total Cost"
liftIO $ totalCost `shouldBe`
if | actualPgVersion > pgVersion120 -> Just [aesonQQ|130.44|]
| actualPgVersion > pgVersion100 -> Just [aesonQQ|69.34|]
| otherwise -> Just [aesonQQ|70.79|]
if | actualPgVersion > pgVersion120 -> Just [aesonQQ|69.34|]
| actualPgVersion > pgVersion100 -> Just [aesonQQ|69.36|]
| otherwise -> Just [aesonQQ|70.81|]
disabledSpec :: SpecWith ((), Application)
disabledSpec =