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release-25.3.7-rc: sql: add distsql_prevent_partitioning_soft_limited_scans #160604

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Merged
michae2 merged 1 commit into from
Jan 7, 2026
Merged

release-25.3.7-rc: sql: add distsql_prevent_partitioning_soft_limited_scans #160604

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11 changes: 4 additions & 7 deletions pkg/sql/distsql_physical_planner.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2435,14 +2435,11 @@ func (dsp *DistSQLPlanner) planTableReaders(
ignoreMisplannedRanges bool
err error
)
sd := planCtx.ExtendedEvalCtx.SessionData()
if planCtx.isLocal {
spanPartitions, parallelizeLocal = dsp.maybeParallelizeLocalScans(ctx, planCtx, info)
} else if info.post.Limit == 0 {
// No hard limit - plan all table readers where their data live. Note
// that we're ignoring soft limits for now since the TableReader will
// still read too eagerly in the soft limit case. To prevent this we'll
// need a new mechanism on the execution side to modulate table reads.
// TODO(yuzefovich): add that mechanism.
} else if info.post.Limit == 0 && (info.spec.LimitHint == 0 || !sd.DistSQLPreventPartitioningSoftLimitedScans) {
// No limits - plan all table readers where their data live.
bound := PartitionSpansBoundDefault
if info.desc.NumFamilies() > 1 {
bound = PartitionSpansBoundCFWithinRow
Expand All @@ -2452,7 +2449,7 @@ func (dsp *DistSQLPlanner) planTableReaders(
return err
}
} else {
// If the scan has a hard limit, use a single TableReader to avoid
// If the scan has a hard or soft limit, use a single TableReader to avoid
// reading more rows than necessary.
sqlInstanceID, err := dsp.getInstanceIDForScan(ctx, planCtx, info.spans, info.reverse)
if err != nil {
Expand Down
4 changes: 4 additions & 0 deletions pkg/sql/exec_util.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4309,6 +4309,10 @@ func (m *sessionDataMutator) SetUseImprovedRoutineDepsTriggersAndComputedCols(va
m.data.UseImprovedRoutineDepsTriggersAndComputedCols = val
}

func (m *sessionDataMutator) SetDistSQLPreventPartitioningSoftLimitedScans(val bool) {
m.data.DistSQLPreventPartitioningSoftLimitedScans = val
}

// Utility functions related to scrubbing sensitive information on SQL Stats.

// quantizeCounts ensures that the Count field in the
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1 change: 1 addition & 0 deletions pkg/sql/logictest/testdata/logic_test/information_schema
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Original file line number Diff line number Diff line change
Expand Up @@ -3982,6 +3982,7 @@ distribute_join_row_count_threshold 1000
distribute_scan_row_count_threshold 10000
distribute_sort_row_count_threshold 1000
distsql_plan_gateway_bias 2
distsql_prevent_partitioning_soft_limited_scans off
distsql_use_reduced_leaf_write_sets on
enable_auto_rehoming off
enable_create_stats_using_extremes on
Expand Down
3 changes: 3 additions & 0 deletions pkg/sql/logictest/testdata/logic_test/pg_catalog
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Original file line number Diff line number Diff line change
Expand Up @@ -2986,6 +2986,7 @@ distribute_scan_row_count_threshold 10000
distribute_sort_row_count_threshold 1000 NULL NULL NULL string
distsql off NULL NULL NULL string
distsql_plan_gateway_bias 2 NULL NULL NULL string
distsql_prevent_partitioning_soft_limited_scans off NULL NULL NULL string
distsql_use_reduced_leaf_write_sets on NULL NULL NULL string
enable_auto_rehoming off NULL NULL NULL string
enable_create_stats_using_extremes on NULL NULL NULL string
Expand Down Expand Up @@ -3231,6 +3232,7 @@ distribute_scan_row_count_threshold 10000
distribute_sort_row_count_threshold 1000 NULL user NULL 1000 1000
distsql off NULL user NULL off off
distsql_plan_gateway_bias 2 NULL user NULL 2 2
distsql_prevent_partitioning_soft_limited_scans off NULL user NULL off off
distsql_use_reduced_leaf_write_sets on NULL user NULL on on
enable_auto_rehoming off NULL user NULL off off
enable_create_stats_using_extremes on NULL user NULL on on
Expand Down Expand Up @@ -3463,6 +3465,7 @@ distribute_scan_row_count_threshold NULL NULL
distribute_sort_row_count_threshold NULL NULL NULL NULL NULL
distsql NULL NULL NULL NULL NULL
distsql_plan_gateway_bias NULL NULL NULL NULL NULL
distsql_prevent_partitioning_soft_limited_scans NULL NULL NULL NULL NULL
distsql_use_reduced_leaf_write_sets NULL NULL NULL NULL NULL
distsql_workmem NULL NULL NULL NULL NULL
enable_auto_rehoming NULL NULL NULL NULL NULL
Expand Down
1 change: 1 addition & 0 deletions pkg/sql/logictest/testdata/logic_test/show_source
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,7 @@ distribute_scan_row_count_threshold 10000
distribute_sort_row_count_threshold 1000
distsql off
distsql_plan_gateway_bias 2
distsql_prevent_partitioning_soft_limited_scans off
distsql_use_reduced_leaf_write_sets on
enable_auto_rehoming off
enable_create_stats_using_extremes on
Expand Down
160 changes: 160 additions & 0 deletions pkg/sql/opt/exec/execbuilder/testdata/distsql_scan
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Original file line number Diff line number Diff line change
@@ -0,0 +1,160 @@
# LogicTest: 5node

# Regression test for lazy reading of soft-limited scans.

statement ok
CREATE TABLE abc (a INT PRIMARY KEY, b INT, c STRING, FAMILY (a, b, c))

statement ok
INSERT INTO abc SELECT i, i % 10, repeat('c', 16384) FROM generate_series(0, 99) AS s(i)

statement ok
ALTER TABLE abc SPLIT AT SELECT i * 20 FROM generate_series(1, 4) AS s(i)

retry
statement ok
ALTER TABLE abc EXPERIMENTAL_RELOCATE
SELECT ARRAY[i+1], i * 20 FROM generate_series(0, 4) as s(i)

# Verify data placement.
query TTTI colnames,rowsort
SELECT start_key, end_key, replicas, lease_holder from [SHOW RANGES FROM TABLE abc WITH DETAILS]
ORDER BY 1
----
start_key end_key replicas lease_holder
<before:/Table/72> …/1/20 {1} 1
…/1/20 …/1/40 {2} 2
…/1/40 …/1/60 {3} 3
…/1/60 …/1/80 {4} 4
…/1/80 <after:/Max> {5} 5

statement ok
ANALYZE abc

query T
EXPLAIN ANALYZE (DISTSQL) SELECT a FROM abc WHERE a >= 0 AND a < 100 ORDER BY a LIMIT 10
----
planning time: 10µs
execution time: 100µs
distribution: <hidden>
vectorized: <hidden>
plan type: custom
rows decoded from KV: 10 (80 B, 20 KVs, 10 gRPC calls)
maximum memory usage: <hidden>
DistSQL network usage: <hidden>
regions: <hidden>
isolation level: serializable
priority: normal
quality of service: regular
·
• scan
sql nodes: <hidden>
kv nodes: <hidden>
regions: <hidden>
actual row count: 10
KV time: 0µs
KV rows decoded: 10
KV pairs read: 20
KV bytes read: 80 B
KV gRPC calls: 10
estimated max memory allocated: 0 B
estimated row count: 10 (10% of the table; stats collected <hidden> ago)
table: abc@abc_pkey
spans: [/0 - /99]
limit: 10
·
Diagram: https://cockroachdb.github.io/distsqlplan/decode.html#eJyMktFq20wQhe__pxjmKgEFr_7elIVCG9ulpnYcZJNSWhNGq4mzWNKquyNsY_xYfYE-WVnJTtrSQPdCaM5-e-asRgcM30rUuBhPx8MlELzP5jOg3MCnD-NsDBcEX1ulXvEbUJfw7mb0pBhIlbqEeTYaZ3D9GQimk9lkCanCBGtX8A1VHFB_wRRXCTbeGQ7B-SgdOmBS7FCrBG3dtBLlVYLGeUZ9QLFSMmpcUl5yxlSwH0TjgoVs2dlSbt5Sbu6bDe8xwaEr26oOGggTXDQUXwfqapCqeG5qKyt9to93ELsHDXXal57X1kVeOEgvia1Yg_rxPZwQtw1QsHEFF_rJJ98LB_BMhYbXCq57dZ3dDsFQWYZnsiHrz-T_UZvdDYcQhBswrq0FLngnA1vLpQY1eAaYNy8BFe2g4sr5PVBZOkMSo_UpchLzyAFcK00rGiLfXeEspApXxwT78vTtg9CaUae_DGsyQq2Oyb_PK-PQuDrwb6N6qZP6o9NVelwlyMWa-58kuNYbvvXOdGxfzjujTig4SL-b9sWkPm8F8UxVH3-V4EPptve2QI3qtK7-8jgvjAdoHeLFFo9u29ku902M9UBl4ARntOERC_vK1jaINajFt3w8_vczAAD__xOuBa4=

query T
EXPLAIN ANALYZE (DISTSQL) SELECT a FROM abc WHERE a >= 0 AND a < 100 AND b != 5 ORDER BY a LIMIT 10
----
planning time: 10µs
execution time: 100µs
distribution: <hidden>
vectorized: <hidden>
plan type: custom
rows decoded from KV: 60 (480 B, 120 KVs, 60 gRPC calls)
maximum memory usage: <hidden>
DistSQL network usage: <hidden>
regions: <hidden>
isolation level: serializable
priority: normal
quality of service: regular
·
• limit
│ count: 10
│
└── • filter
│ sql nodes: <hidden>
│ regions: <hidden>
│ actual row count: 50
│ execution time: 0µs
│ estimated row count: 90
│ filter: b != 5
│
└── • scan
sql nodes: <hidden>
kv nodes: <hidden>
regions: <hidden>
actual row count: 60
KV time: 0µs
KV rows decoded: 60
KV pairs read: 120
KV bytes read: 480 B
KV gRPC calls: 60
estimated max memory allocated: 0 B
estimated row count: 12 - 100 (100% of the table; stats collected <hidden> ago)
table: abc@abc_pkey
spans: [/0 - /99]
·
Diagram: https://cockroachdb.github.io/distsqlplan/decode.html#eJzsV9tu4zYQfe9XTOcpQWWIlC-xCSyQruNFjeaycIwtijZY0NKsV4gkqiRdxw38Wf2BflkhKfJa2ti1AhQIsNaDAQ6HwzlnzpD0I5o_IhR4O7ocDacg4d3k5grkzIdffhpNRnByIuH3BWNtegPsFH68voDS4gNn7PTJNoPv30D3FG4mF6MJvP0VJFyOr8ZT4AwdTFRA1zImg-I35Oighw620cEOOtjFOwdTrXwyRunM5TFfMA4eUDAHwyRd2Mx856CvNKF4RBvaiFDgVM4impAMSLvZRgFZGUb5NnLmn8uZ_zG9pxU6OFTRIk6MAOnADB28TWU2clnL9bKVP3-AbFMjIOHFUNM8VJmPJWMLkw1jEsD--ds8uailgYB8FVAggHuFdbayZECTDAQMevC2sM4n74fgyygyXzxTGerS08u4uPowHIKxlIKvFomFE3qwbpjYUwEsB1g4EN3vcojlA8QUK70CGUXKlzZLjeVZzKT1P5MBtbDpwgrI_HMIpYF7eLd2sBg-UW6snBMKvlWj8QUKtnYOL9O7MLKkSbvdao0Ku4BzL5ePEGJ8Pe2jg5dhHNpCO_RA_sKGKqmy_99Y2E4sXg1LdyeWLxCUDkhTUM3_nP-Ad-tnAF-rlkpdXpPkTZbXOf_f8bVr-Hi1WPzwnuIv6imPtdzOsamaNxVvUqdNU_VeZVP1Kli8wzXnvUhzHdZye0fNNdec16ROG82dvUrNnVWwtA_XXPtFmuuxlts_aq655tpN6rTRXP9Vaq5fwdI5XHOdF2muz1ouZ0fRNRddp0mhNqIbvErRDZq8vidkUpUYqiDZtROr7dTi2fuWgjkV72GjFtqn91r5uW8xvMkD5YaAjC1meTEYJ-WUsZpkvPnzsB2J743kVSLx7UjdeiRvf05NkmrvDdXZHYnXI3WawpN5VTAhu1T6HiJpKfFXGymV9qUMbVVkARnSoYzCv-TXCiyX5arT5FP4Z34KsK258igoJ_tFI5bTMRkj5xWP7qHa3qaoV6eou5ei3m6yvXqk3pHsGtlndYrO9lLU3012ux6pfyS7Rna_TtFg_4nEdrPd-eqY3H_ifot0D7Lr6VOklh_DAAWyp6_1zE_5YbZAzk12R95-Vsucr-kqzW64TzIy5OCVvKcLsqTjMAmNDX0UVi9ovf7u3wAAAP__qpTOfA==

statement ok
SET distsql_prevent_partitioning_soft_limited_scans = on

query T
EXPLAIN ANALYZE (DISTSQL) SELECT a FROM abc WHERE a >= 0 AND a < 100 AND b != 5 ORDER BY a LIMIT 10
----
planning time: 10µs
execution time: 100µs
distribution: <hidden>
vectorized: <hidden>
plan type: generic, reused
rows decoded from KV: 12 (96 B, 24 KVs, 12 gRPC calls)
maximum memory usage: <hidden>
DistSQL network usage: <hidden>
regions: <hidden>
isolation level: serializable
priority: normal
quality of service: regular
·
• limit
│ count: 10
│
└── • filter
│ sql nodes: <hidden>
│ regions: <hidden>
│ actual row count: 10
│ execution time: 0µs
│ estimated row count: 90
│ filter: b != 5
│
└── • scan
sql nodes: <hidden>
kv nodes: <hidden>
regions: <hidden>
actual row count: 12
KV time: 0µs
KV rows decoded: 12
KV pairs read: 24
KV bytes read: 96 B
KV gRPC calls: 12
estimated max memory allocated: 0 B
estimated row count: 12 - 100 (100% of the table; stats collected <hidden> ago)
table: abc@abc_pkey
spans: [/0 - /99]
·
Diagram: https://cockroachdb.github.io/distsqlplan/decode.html#eJyUUt1q20wQvf-eYr65imGDV-4P7UIgje1Q0zgOikkprQmr1cRZImnV3RGxCX6svkCfrKxkt0lo0lYXgjl79sycPXOH4WuBCs_HJ-PhHDQcp7Mp6MzAx_fjdAx7exq-NFK-oAOQPXh3OoIdYiCRsrfFMvj_AF71YJaOxikcfQINJ5PpZA6JRIGVy-lUlxRQfcYEFwJr7wyF4HyE7lrCJF-hkgJtVTcc4YVA4zyhukO2XBAqnOusoJR0Tr4fhXNibYtWVmfmUGfmsr6hNQocuqIpq6BAC8hQ4HmtY9WX-_1ExqsfLiB2DQqqpCs9La2LJKbAHcS2JAXy-7ewpbjbADkZl1OuIBl0aLZmCuBJ5wrevoajDl2mZ0MwuijCL2atrd8xBy9R4PRiOITAVINxTcWwRyvu24p7CmTrsCMQ3TxFKPUKSiqdX4MuCmc0x9FkO0Wm2VxTANdw3bCCyG8t7IBkgIuNwK7cvnlgvSRUyb2QJiNUciP-PqdjWzB58v3kYUgdruBw0O6LUmpyOn-DAmdxmsPIPrGl5W5taEWmYeuqhzn82ZV80tXgkavkX1ylFGpXBXrg6alO8lGn_WSzEEj5krqVD67xhs68My23K2etUAvkFLg7TbpiUu2OAnvS5c9Q7islzyoNnlNaCLwq3O2lzVGh3H77v_ntPowX9DLEJzq_dret7HxdR4NXuggkcKpvaERMvrSVDWwNKvYNbTb__QgAAP__DIZi7A==

statement ok
RESET distsql_prevent_partitioning_soft_limited_scans
2 changes: 1 addition & 1 deletion pkg/sql/opt/exec/execbuilder/tests/5node/BUILD.bazel
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Expand Up @@ -12,7 +12,7 @@ go_test(
"//build/toolchains:is_heavy": {"test.Pool": "heavy"},
"//conditions:default": {"test.Pool": "large"},
}),
shard_count = 28,
shard_count = 29,
tags = ["cpu:3"],
deps = [
"//pkg/base",
Expand Down
7 changes: 7 additions & 0 deletions pkg/sql/opt/exec/execbuilder/tests/5node/generated_test.go
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4 changes: 4 additions & 0 deletions pkg/sql/sessiondatapb/local_only_session_data.proto
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Expand Up @@ -743,6 +743,10 @@ message LocalOnlySessionData {
// triggers or computed columns. The fix applies at routine creation time and
// prevents unnecessary column dependencies from being recorded.
bool use_improved_routine_deps_triggers_and_computed_cols = 196;
// DistSQLPreventPartitioningSoftLimitedScans, when true, prevents the distsql
// physical planner from partitioning scans with soft limits into multiple
// TableReaders. When true, this matches the behavior for hard limits.
bool distsql_prevent_partitioning_soft_limited_scans = 197 [(gogoproto.customname) = "DistSQLPreventPartitioningSoftLimitedScans"];

///////////////////////////////////////////////////////////////////////////
// WARNING: consider whether a session parameter you're adding needs to //
Expand Down
17 changes: 17 additions & 0 deletions pkg/sql/vars.go
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Expand Up @@ -4389,6 +4389,23 @@ var varGen = map[string]sessionVar{
},
GlobalDefault: globalFalse,
},

// CockroachDB extension.
`distsql_prevent_partitioning_soft_limited_scans`: {
GetStringVal: makePostgresBoolGetStringValFn(`distsql_prevent_partitioning_soft_limited_scans`),
Set: func(_ context.Context, m sessionDataMutator, s string) error {
b, err := paramparse.ParseBoolVar("distsql_prevent_partitioning_soft_limited_scans", s)
if err != nil {
return err
}
m.SetDistSQLPreventPartitioningSoftLimitedScans(b)
return nil
},
Get: func(evalCtx *extendedEvalContext, _ *kv.Txn) (string, error) {
return formatBoolAsPostgresSetting(evalCtx.SessionData().DistSQLPreventPartitioningSoftLimitedScans), nil
},
GlobalDefault: globalFalse,
},
}

func ReplicationModeFromString(s string) (sessiondatapb.ReplicationMode, error) {
Expand Down