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opt: add update checks for unique constraints #57930

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Dec 17, 2020
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opt: add update checks for unique constraints #57930

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92 changes: 90 additions & 2 deletions pkg/sql/opt/norm/testdata/rules/prune_cols
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Original file line number Diff line number Diff line change
Expand Up @@ -2585,8 +2585,96 @@ upsert checks
├── upsert_b:16 > 10 [as=check2:18, outer=(16)]
└── column2:7 > upsert_b:16 [as=check3:19, outer=(7,16)]

# TODO(rytaft): test that columns needed for unique checks are not pruned
# from updates.
exec-ddl
CREATE TABLE uniq (
k INT PRIMARY KEY,
v INT,
w INT UNIQUE WITHOUT INDEX,
x INT,
y INT,
z INT UNIQUE,
UNIQUE WITHOUT INDEX (x, y)
)
----

# Do not prune columns from updates that are needed for unique checks.
norm expect=PruneMutationInputCols
UPDATE uniq SET w = 1, x = 2 WHERE k = 3
----
update uniq
├── columns: <none>
├── fetch columns: uniq.k:8 v:9 w:10 x:11 uniq.y:12 z:13
├── update-mapping:
│ ├── w_new:15 => w:3
│ └── x_new:16 => x:4
├── input binding: &1
├── cardinality: [0 - 0]
├── volatile, mutations
├── project
│ ├── columns: w_new:15!null x_new:16!null uniq.k:8!null v:9 w:10 x:11 uniq.y:12 z:13
│ ├── cardinality: [0 - 1]
│ ├── key: ()
│ ├── fd: ()-->(8-13,15,16)
│ ├── select
│ │ ├── columns: uniq.k:8!null v:9 w:10 x:11 uniq.y:12 z:13
│ │ ├── cardinality: [0 - 1]
│ │ ├── key: ()
│ │ ├── fd: ()-->(8-13)
│ │ ├── scan uniq
│ │ │ ├── columns: uniq.k:8!null v:9 w:10 x:11 uniq.y:12 z:13
│ │ │ ├── key: (8)
│ │ │ └── fd: (8)-->(9-13), (13)~~>(8-12)
│ │ └── filters
│ │ └── uniq.k:8 = 3 [outer=(8), constraints=(/8: [/3 - /3]; tight), fd=()-->(8)]
│ └── projections
│ ├── 1 [as=w_new:15]
│ └── 2 [as=x_new:16]
└── unique-checks
├── unique-checks-item: uniq(w)
│ └── semi-join (hash)
│ ├── columns: w_new:17!null k:18!null
│ ├── cardinality: [0 - 1]
│ ├── key: ()
│ ├── fd: ()-->(17,18)
│ ├── with-scan &1
│ │ ├── columns: w_new:17!null k:18!null
│ │ ├── mapping:
│ │ │ ├── w_new:15 => w_new:17
│ │ │ └── uniq.k:8 => k:18
│ │ ├── cardinality: [0 - 1]
│ │ ├── key: ()
│ │ └── fd: ()-->(17,18)
│ ├── scan uniq
│ │ ├── columns: uniq.k:19!null w:21
│ │ ├── key: (19)
│ │ └── fd: (19)-->(21)
│ └── filters
│ ├── w_new:17 = w:21 [outer=(17,21), constraints=(/17: (/NULL - ]; /21: (/NULL - ]), fd=(17)==(21), (21)==(17)]
│ └── k:18 != uniq.k:19 [outer=(18,19), constraints=(/18: (/NULL - ]; /19: (/NULL - ])]
└── unique-checks-item: uniq(x,y)
└── semi-join (hash)
├── columns: x_new:26!null y:27 k:28!null
├── cardinality: [0 - 1]
├── key: ()
├── fd: ()-->(26-28)
├── with-scan &1
│ ├── columns: x_new:26!null y:27 k:28!null
│ ├── mapping:
│ │ ├── x_new:16 => x_new:26
│ │ ├── uniq.y:12 => y:27
│ │ └── uniq.k:8 => k:28
│ ├── cardinality: [0 - 1]
│ ├── key: ()
│ └── fd: ()-->(26-28)
├── scan uniq
│ ├── columns: uniq.k:29!null x:32 uniq.y:33
│ ├── key: (29)
│ └── fd: (29)-->(32,33)
└── filters
├── x_new:26 = x:32 [outer=(26,32), constraints=(/26: (/NULL - ]; /32: (/NULL - ]), fd=(26)==(32), (32)==(26)]
├── y:27 = uniq.y:33 [outer=(27,33), constraints=(/27: (/NULL - ]; /33: (/NULL - ]), fd=(27)==(33), (33)==(27)]
└── k:28 != uniq.k:29 [outer=(28,29), constraints=(/28: (/NULL - ]; /29: (/NULL - ])]


# ------------------------------------------------------------------------------
# PruneMutationReturnCols
Expand Down
70 changes: 52 additions & 18 deletions pkg/sql/opt/optbuilder/mutation_builder_unique.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,33 +21,18 @@ import (
)

// buildUniqueChecksForInsert builds uniqueness check queries for an insert.
// These check queries are used to enforce UNIQUE WITHOUT INDEX constraints.
func (mb *mutationBuilder) buildUniqueChecksForInsert() {
uniqueCount := mb.tab.UniqueCount()
if uniqueCount == 0 {
// No relevant unique checks.
return
}

// We only need to build unique checks if there is at least one unique
// constraint without an index.
needChecks := false
i := 0
for ; i < uniqueCount; i++ {
if mb.tab.Unique(i).WithoutIndex() {
needChecks = true
break
}
}
if !needChecks {
if !mb.hasUniqueWithoutIndexConstraints() {
return
}

mb.ensureWithID()
h := &mb.uniqueCheckHelper

// i is already set to the index of the first uniqueness check without an
// index, so start iterating from there.
for ; i < uniqueCount; i++ {
for i, n := 0, mb.tab.UniqueCount(); i < n; i++ {
// If this constraint is already enforced by an index we don't need to plan
// a check.
if mb.tab.Unique(i).WithoutIndex() && h.init(mb, i) {
Expand All @@ -57,6 +42,55 @@ func (mb *mutationBuilder) buildUniqueChecksForInsert() {
telemetry.Inc(sqltelemetry.UniqueChecksUseCounter)
}

// buildUniqueChecksForUpdate builds uniqueness check queries for an update.
// These check queries are used to enforce UNIQUE WITHOUT INDEX constraints.
func (mb *mutationBuilder) buildUniqueChecksForUpdate() {
// We only need to build unique checks if there is at least one unique
// constraint without an index.
if !mb.hasUniqueWithoutIndexConstraints() {
return
}

mb.ensureWithID()
h := &mb.uniqueCheckHelper

for i, n := 0, mb.tab.UniqueCount(); i < n; i++ {
// If this constraint is already enforced by an index or doesn't include
// the updated columns we don't need to plan a check.
if mb.tab.Unique(i).WithoutIndex() && mb.uniqueColsUpdated(i) && h.init(mb, i) {
// The insertion check works for updates too since it simply checks that
// the unique columns in the newly inserted or updated rows do not match
// any existing rows. The check prevents rows from matching themselves by
// adding a filter based on the primary key.
mb.uniqueChecks = append(mb.uniqueChecks, h.buildInsertionCheck())
}
}
telemetry.Inc(sqltelemetry.UniqueChecksUseCounter)
}

// hasUniqueWithoutIndexConstraints returns true if there are any
// UNIQUE WITHOUT INDEX constraints on the table.
func (mb *mutationBuilder) hasUniqueWithoutIndexConstraints() bool {
for i, n := 0, mb.tab.UniqueCount(); i < n; i++ {
if mb.tab.Unique(i).WithoutIndex() {
return true
}
}
return false
}

// uniqueColsUpdated returns true if any of the columns for a unique
// constraint are being updated (according to updateColIDs).
func (mb *mutationBuilder) uniqueColsUpdated(uniqueOrdinal int) bool {
uc := mb.tab.Unique(uniqueOrdinal)
for i, n := 0, uc.ColumnCount(); i < n; i++ {
if ord := uc.ColumnOrdinal(mb.tab, i); mb.updateColIDs[ord] != 0 {
return true
}
}
return false
}

// uniqueCheckHelper is a type associated with a single unique constraint and
// is used to build the "leaves" of a unique check expression, namely the
// WithScan of the mutation input and the Scan of the table.
Expand Down
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