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opt: fix bug in histogram calculation for TimeTZ
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This commit fixes a bug in the histogram estimation code for TimeTZ
that made the faulty assumption that TimeTZ values are ordered by
TimeOfDay. This is incorrect since it does not take the OffsetSecs
into account. As a result, it was possible to estimate that the size
of a histogram bucket was negative, which caused problems in the
statistics estimation code. This commit fixes the problem by taking
into account both TimeOfDay and OffsetSecs when estimating the size of
a bucket in a TimeTZ histogram.

Fixes cockroachdb#74667

Release note (bug fix): Fixed an internal error, "estimated row count must
be non-zero", that could occur during planning for queries over a table
with a TimeTZ column. This error was due to a faulty assumption in the
statistics estimation code about ordering of TimeTZ values, which has now
been fixed. The error could occur when TimeTZ values used in the query had
a different time zone offset than the TimeTZ values stored in the table.
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@rytaft
rytaft committed Jan 19, 2022
1 parent 24406d9 commit 7653908
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Showing 4 changed files with 149 additions and 12 deletions.
73 changes: 73 additions & 0 deletions pkg/sql/opt/memo/testdata/stats/groupby
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Original file line number Diff line number Diff line change
Expand Up @@ -526,3 +526,76 @@ project
│ └── bool_or:5 [type=bool, outer=(5), constraints=(/5: [/true - /true]; tight), fd=()-->(5)]
└── projections
└── 1 [as="?column?":6, type=int]

# Regression test for #74667.
exec-ddl
CREATE TABLE t74667 (col TIMETZ PRIMARY KEY)
----

exec-ddl
ALTER TABLE t74667 INJECT STATISTICS '[
{
"columns": [
"col"
],
"created_at": "2000-01-01 00:00:00+00:00",
"distinct_count": 950814763580487611,
"histo_buckets": [
{
"distinct_range": 0,
"num_eq": 3873172219268179689,
"num_range": 0,
"upper_bound": "00:00:00+15:59:00"
},
{
"distinct_range": 400000,
"num_eq": 3000000000,
"num_range": 400000,
"upper_bound": "04:40:23.558699+11:08:00"
},
{
"distinct_range": 381143202295070850,
"num_eq": 6399369578112136136,
"num_range": 381143202295070816,
"upper_bound": "06:12:15.740051+06:40:00"
}
],
"histo_col_type": "TIMETZ",
"name": "__auto__",
"null_count": 0,
"row_count": 1188522479222658429
}
]'
----

norm
SELECT count(*)
FROM t74667
WHERE col < '03:33:05.598931+07:11:00':::TIMETZ
GROUP BY col;
----
project
├── columns: count:4(int!null)
├── stats: [rows=2.00509067e+16]
└── group-by (hash)
├── columns: col:1(timetz!null) count_rows:4(int!null)
├── grouping columns: col:1(timetz!null)
├── stats: [rows=2.00509067e+16, distinct(1)=2.00509067e+16, null(1)=0]
├── key: (1)
├── fd: (1)-->(4)
├── select
│ ├── columns: col:1(timetz!null)
│ ├── stats: [rows=4.52141047e+17, distinct(1)=2.00509067e+16, null(1)=0]
│ │ histogram(1)= 0 4.3209e+17 44624 3.3468e+08 2.0051e+16 0
│ │ <--- '00:00:00+15:59:00' ------- '04:40:23.558699+11:08:00' ------------ '03:33:06.598931+07:11:01'
│ ├── key: (1)
│ ├── scan t74667
│ │ ├── columns: col:1(timetz!null)
│ │ ├── stats: [rows=1.18852248e+18, distinct(1)=9.50814764e+17, null(1)=0]
│ │ │ histogram(1)= 0 4.3209e+17 44624 3.3468e+08 4.252e+16 7.1391e+17
│ │ │ <--- '00:00:00+15:59:00' ------- '04:40:23.558699+11:08:00' ----------- '06:12:15.740051+06:40:00'
│ │ └── key: (1)
│ └── filters
│ └── col:1 < '03:33:05.598931+07:11:00' [type=bool, outer=(1), constraints=(/1: (/NULL - /'03:33:06.598931+07:11:01']; tight)]
└── aggregations
└── count-rows [as=count_rows:4, type=int]
1 change: 1 addition & 0 deletions pkg/sql/opt/props/BUILD.bazel
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ go_library(
"//pkg/sql/types",
"//pkg/util/encoding",
"//pkg/util/log",
"//pkg/util/timetz",
"@com_github_cockroachdb_errors//:errors",
"@com_github_olekukonko_tablewriter//:tablewriter",
],
Expand Down
17 changes: 14 additions & 3 deletions pkg/sql/opt/props/histogram.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ import (
"io"
"math"
"sort"
"time"

"github.com/cockroachdb/cockroach/pkg/sql/inverted"
"github.com/cockroachdb/cockroach/pkg/sql/opt"
Expand All @@ -26,6 +27,7 @@ import (
"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
"github.com/cockroachdb/cockroach/pkg/sql/types"
"github.com/cockroachdb/cockroach/pkg/util/encoding"
"github.com/cockroachdb/cockroach/pkg/util/timetz"
"github.com/cockroachdb/errors"
"github.com/olekukonko/tablewriter"
)
Expand Down Expand Up @@ -785,9 +787,18 @@ func getRangesBeforeAndAfter(
return rng, true

case types.TimeTZFamily:
lower := lowerBound.(*tree.DTimeTZ).TimeOfDay
upper := upperBound.(*tree.DTimeTZ).TimeOfDay
rng = float64(upper) - float64(lower)
// timeTZOffsetSecsRange is the total number of possible values for offset.
timeTZOffsetSecsRange := timetz.MaxTimeTZOffsetSecs - timetz.MinTimeTZOffsetSecs + 1

// Find the range in microseconds based on the absolute times of the range
// boundaries.
lower := lowerBound.(*tree.DTimeTZ)
upper := upperBound.(*tree.DTimeTZ)
rng = float64(upper.ToTime().Sub(lower.ToTime()) / time.Microsecond)

// Account for the offset.
rng *= float64(timeTZOffsetSecsRange)
rng += float64(upper.OffsetSecs - lower.OffsetSecs)
return rng, true

default:
Expand Down
70 changes: 61 additions & 9 deletions pkg/sql/opt/props/histogram_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -384,7 +384,7 @@ func TestFilterBucket(t *testing.T) {
t.Fatalf("for span %s expected an error", testCase.span)
}
if !reflect.DeepEqual(testCase.expected, actual) {
t.Fatalf("for span %s exected %v but found %v", testCase.span, testCase.expected, actual)
t.Errorf("for span %s exected %v but found %v", testCase.span, testCase.expected, actual)
}
}
}
Expand Down Expand Up @@ -612,36 +612,88 @@ func TestFilterBucket(t *testing.T) {
})

t.Run("timetz", func(t *testing.T) {
upperBound, _, err := tree.ParseDTimeTZ(&evalCtx, "05:00:00", time.Microsecond)
upperBound1, _, err := tree.ParseDTimeTZ(&evalCtx, "05:00:00", time.Microsecond)
if err != nil {
t.Fatal(err)
}
lowerBound, _, err := tree.ParseDTimeTZ(&evalCtx, "04:00:00", time.Microsecond)
lowerBound1, _, err := tree.ParseDTimeTZ(&evalCtx, "04:00:00", time.Microsecond)
if err != nil {
t.Fatal(err)
}
h := &Histogram{evalCtx: &evalCtx, col: col, buckets: []cat.HistogramBucket{
{NumEq: 0, NumRange: 0, DistinctRange: 0, UpperBound: getPrevUpperBound(lowerBound)},
{NumEq: 1, NumRange: 62, DistinctRange: 31, UpperBound: upperBound},
h1 := &Histogram{evalCtx: &evalCtx, col: col, buckets: []cat.HistogramBucket{
{NumEq: 0, NumRange: 0, DistinctRange: 0, UpperBound: getPrevUpperBound(lowerBound1)},
{NumEq: 1, NumRange: 62, DistinctRange: 31, UpperBound: upperBound1},
}}

ub1, _, err := tree.ParseDTimeTZ(&evalCtx, "04:15:00", time.Microsecond)
if err != nil {
t.Fatal(err)
}

testData := []testCase{
testData1 := []testCase{
{
span: "[/04:00:00 - /04:15:00]",
expected: &cat.HistogramBucket{NumEq: 0, NumRange: 15.5, DistinctRange: 7.75, UpperBound: ub1},
},
{
span: "[/04:30:00 - /05:00:00]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 31, DistinctRange: 15.5, UpperBound: upperBound},
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 31, DistinctRange: 15.5, UpperBound: upperBound1},
},
{
span: "[/06:30:00+02:00:00 - /05:00:00]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 31, DistinctRange: 15.5, UpperBound: upperBound1},
},
{
span: "[/08:30:00+04:00:00 - /05:00:00]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 31, DistinctRange: 15.5, UpperBound: upperBound1},
},
}

// This test distinguishes between values that have the same time but
// different offsets.
upperBound2, _, err := tree.ParseDTimeTZ(&evalCtx, "05:00:00.000001", time.Microsecond)
if err != nil {
t.Fatal(err)
}
h2 := &Histogram{evalCtx: &evalCtx, col: col, buckets: []cat.HistogramBucket{
{NumEq: 0, NumRange: 0, DistinctRange: 0, UpperBound: upperBound1},
{NumEq: 1, NumRange: 10000, DistinctRange: 1000, UpperBound: upperBound2},
}}

ub2, _, err := tree.ParseDTimeTZ(&evalCtx, "20:59:00.000001+15:59:00", time.Microsecond)
if err != nil {
t.Fatal(err)
}

testData2 := []testCase{
{
span: "[/05:00:00.000001 - /05:00:00.000001]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 0, DistinctRange: 0, UpperBound: upperBound2},
},
{
span: "[/07:00:00.000001+02:00:00 - /05:00:00.000001]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 625.65, DistinctRange: 62.57, UpperBound: upperBound2},
},
{
span: "[/09:00:00.000001+04:00:00 - /05:00:00.000001]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 1251.3, DistinctRange: 125.13, UpperBound: upperBound2},
},
{
span: "[/04:59:59-00:00:01 - /20:59:00.000001+15:59:00]",
expected: &cat.HistogramBucket{NumEq: 0, NumRange: 5000, DistinctRange: 500, UpperBound: ub2},
},
{
span: "[/20:59:00.000001+15:59:00 - /05:00:00.000001]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 5000, DistinctRange: 500, UpperBound: upperBound2},
},
{
span: "[/04:59:58-00:00:02 - /05:00:00.000001]",
expected: &cat.HistogramBucket{NumEq: 1, NumRange: 9999.91, DistinctRange: 999.99, UpperBound: upperBound2},
},
}

runTest(h, testData, types.TimeTZFamily)
runTest(h1, testData1, types.TimeTZFamily)
runTest(h2, testData2, types.TimeTZFamily)
})

t.Run("string", func(t *testing.T) {
Expand Down

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