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proto: add paging_size_bytes to coprocessor.Request#1448

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Jun 11, 2026
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proto: add paging_size_bytes to coprocessor.Request#1448
ti-chi-bot[bot] merged 1 commit into
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JmPotato:demo/ru-paging-size

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@JmPotato JmPotato commented Apr 2, 2026 •
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What is changed and how it works?

Add a new paging_size_bytes field (field 17, uint64) to the coprocessor.Request message.

  • When paging_size_bytes is 0, the feature is disabled (backward compatible).
  • When set to a positive value, TiKV will stop scanning the current page once accumulated scanned bytes reach this limit and return the page boundary so the next page can resume from there.

Note: paging_size_bytes is intentionally distinct from the existing max_keys_read (field 16). max_keys_read is a per-task hard ceiling on storage-engine keys scanned, applied uniformly to any coprocessor request. paging_size_bytes is a paging-only, byte-granularity dimension intended for Resource Control: it bounds the byte volume of a single page so RU pre-charging in PD's resource controller can be performed at byte granularity, complementing the existing row-count-based paging (paging_size). The two fields target different scenarios and may be set independently.

Why is this needed?

In concurrent coprocessor workloads under Resource Control, row-count-based paging alone cannot prevent "token cliff" effects where multiple workers exhaust RU budgets simultaneously. A byte-based budget provides finer-grained control for RU pre-charging in PD's resource controller.

Related PRs

@ti-chi-bot ti-chi-bot Bot requested review from fzzf678 and pingyu April 2, 2026 02:41
@ti-chi-bot ti-chi-bot Bot added the size/L label Apr 2, 2026
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@JmPotato JmPotato marked this pull request as draft April 7, 2026 09:46
@JmPotato JmPotato force-pushed the demo/ru-paging-size branch 3 times, most recently from 48951e0 to 042bfc7 Compare April 28, 2026 06:36
@ti-chi-bot ti-chi-bot Bot added size/XL and removed size/L labels Apr 28, 2026
This was referenced Apr 28, 2026
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@JmPotato JmPotato marked this pull request as ready for review April 28, 2026 07:15
@ti-chi-bot ti-chi-bot Bot requested review from Tristan1900 and js00070 April 28, 2026 07:15
@YuhaoZhang00 YuhaoZhang00 mentioned this pull request Apr 28, 2026
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@JmPotato JmPotato force-pushed the demo/ru-paging-size branch from 042bfc7 to a6a24f9 Compare June 8, 2026 06:57
@JmPotato
proto: add paging_size_bytes to coprocessor.Request
c2edc88 
Add a new uint64 field `paging_size_bytes` (field 17) to the
coprocessor Request message. When set, TiKV will stop scanning
when accumulated scanned bytes reach this limit, enabling
byte-budget paging for finer-grained Resource Control.

Note: rebased onto upstream master where field 16 is now taken
by max_keys_read (pingcap#1450), so paging_size_bytes was bumped from
field 16 to field 17.

Signed-off-by: JmPotato <github@ipotato.me>
@JmPotato JmPotato force-pushed the demo/ru-paging-size branch from a6a24f9 to c2edc88 Compare June 11, 2026 08:14
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@lhy1024: adding LGTM is restricted to approvers and reviewers in OWNERS files.

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@ti-chi-bot ti-chi-bot Bot added the lgtm label Jun 11, 2026
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, lhy1024, rleungx, YuhaoZhang00

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[LGTM Timeline notifier]

Timeline:

  • 2026-05-18 03:22:10.355002663 +0000 UTC m=+148059.859133339: ☑️ agreed by rleungx.
  • 2026-06-11 08:22:28.159639647 +0000 UTC m=+1034649.229957037: ☑️ agreed by cfzjywxk.

@ti-chi-bot ti-chi-bot Bot merged commit a15c348 into pingcap:master Jun 11, 2026
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@JmPotato JmPotato deleted the demo/ru-paging-size branch June 11, 2026 08:46
@JmPotato JmPotato mentioned this pull request Jun 11, 2026
Open
JmPotato added a commit to JmPotato/tidb that referenced this pull request Jun 26, 2026
@JmPotato
*: add tidb_paging_size_bytes and forward it to coprocessor RPC
0711b03 
Add a TiDB-side knob `tidb_paging_size_bytes` (global+session sysvar,
default 0) and plumb the value end-to-end so it lands as the new
`paging_size_bytes` field on `coprocessor.Request`.

- `tidb_paging_size_bytes` is allowed in `SET_VAR` hints; default 0
  disables byte-budget paging.
- The value flows through `DistSQLContext` into
  `kv.Request.Paging.PagingSizeBytes` via `RequestBuilder`.
- In the cop client, `pagingBytesEligible` gates the feature to
  TiKV + DAG requests. When the byte budget is positive on an
  eligible request whose row-count paging is disabled, paging is
  force-enabled with minimum row parameters so the byte budget
  becomes the dominant page-break signal. This must happen before
  `checkStoreBatchCopr` because batch copr is incompatible with
  paging.
- The byte budget is carried on each generated `copTask`,
  populates `coprocessor.Request.PagingSizeBytes` on outgoing
  RPCs, propagates onto retried tasks (region/lock errors), and
  is cleared together with `pagingSize` when the small-limit
  downgrade fires.

Dependency:

- Pin `pingcap/kvproto` to JmPotato/kvproto demo/ru-paging-size
  which adds `paging_size_bytes` (tag 17) to `coprocessor.Request`
  via pingcap/kvproto#1448; revert this replace once that PR is
  merged and tagged.

Tests:

- `TestPagingBytesEligible` covers eligibility for TiKV/DAG vs
  TiFlash and non-DAG requests.
- `TestBuildCopTasksWithPagingSizeBytes` covers task construction
  with and without small-limit downgrade.
- `tests/integrationtest/sessionctx/setvar` is extended to cover
  the new sysvar (default, set, set via SET_VAR hint).

Signed-off-by: JmPotato <github@ipotato.me>
JmPotato added a commit to JmPotato/tidb that referenced this pull request Jun 29, 2026
@JmPotato
*: add tidb_paging_size_bytes and forward it to coprocessor RPC
cfb06b1 
Add a TiDB-side knob `tidb_paging_size_bytes` (global+session sysvar,
default 0) and plumb the value end-to-end so it lands as the new
`paging_size_bytes` field on `coprocessor.Request`.

- `tidb_paging_size_bytes` is allowed in `SET_VAR` hints; default 0
  disables byte-budget paging.
- The value flows through `DistSQLContext` into
  `kv.Request.Paging.PagingSizeBytes` via `RequestBuilder`.
- In the cop client, `pagingBytesEligible` gates the feature to
  TiKV + DAG requests. When the byte budget is positive on an
  eligible request whose row-count paging is disabled, paging is
  force-enabled with minimum row parameters so the byte budget
  becomes the dominant page-break signal. This must happen before
  `checkStoreBatchCopr` because batch copr is incompatible with
  paging.
- The byte budget is carried on each generated `copTask`,
  populates `coprocessor.Request.PagingSizeBytes` on outgoing
  RPCs, propagates onto retried tasks (region/lock errors), and
  is cleared together with `pagingSize` when the small-limit
  downgrade fires.

Dependency:

- Pin `pingcap/kvproto` to JmPotato/kvproto demo/ru-paging-size
  which adds `paging_size_bytes` (tag 17) to `coprocessor.Request`
  via pingcap/kvproto#1448; revert this replace once that PR is
  merged and tagged.

Tests:

- `TestPagingBytesEligible` covers eligibility for TiKV/DAG vs
  TiFlash and non-DAG requests.
- `TestBuildCopTasksWithPagingSizeBytes` covers task construction
  with and without small-limit downgrade.
- `tests/integrationtest/sessionctx/setvar` is extended to cover
  the new sysvar (default, set, set via SET_VAR hint).

Signed-off-by: JmPotato <github@ipotato.me>
JmPotato added a commit to JmPotato/tidb that referenced this pull request Jun 29, 2026
@JmPotato
*: add tidb_paging_size_bytes and forward it to coprocessor RPC
1b4314e 
Add a TiDB-side knob `tidb_paging_size_bytes` (global+session sysvar,
default 0) and plumb the value end-to-end so it lands as the new
`paging_size_bytes` field on `coprocessor.Request`.

- `tidb_paging_size_bytes` is allowed in `SET_VAR` hints; default 0
  disables byte-budget paging.
- The value flows through `DistSQLContext` into
  `kv.Request.Paging.PagingSizeBytes` via `RequestBuilder`.
- In the cop client, `pagingBytesEligible` gates the feature to
  TiKV + DAG requests. When the byte budget is positive on an
  eligible request whose row-count paging is disabled, paging is
  force-enabled with minimum row parameters so the byte budget
  becomes the dominant page-break signal. This must happen before
  `checkStoreBatchCopr` because batch copr is incompatible with
  paging.
- The byte budget is carried on each generated `copTask`,
  populates `coprocessor.Request.PagingSizeBytes` on outgoing
  RPCs, propagates onto retried tasks (region/lock errors), and
  is cleared together with `pagingSize` when the small-limit
  downgrade fires.

Dependency:

- Pin `pingcap/kvproto` to JmPotato/kvproto demo/ru-paging-size
  which adds `paging_size_bytes` (tag 17) to `coprocessor.Request`
  via pingcap/kvproto#1448; revert this replace once that PR is
  merged and tagged.

Tests:

- `TestPagingBytesEligible` covers eligibility for TiKV/DAG vs
  TiFlash and non-DAG requests.
- `TestBuildCopTasksWithPagingSizeBytes` covers task construction
  with and without small-limit downgrade.
- `tests/integrationtest/sessionctx/setvar` is extended to cover
  the new sysvar (default, set, set via SET_VAR hint).

Signed-off-by: JmPotato <github@ipotato.me>
JmPotato added a commit to JmPotato/tidb that referenced this pull request Jun 29, 2026
@JmPotato
*: add tidb_paging_size_bytes and forward it to coprocessor RPC
e469694 
Add a TiDB-side knob `tidb_paging_size_bytes` (global+session sysvar,
default 0) and plumb the value end-to-end so it lands as the new
`paging_size_bytes` field on `coprocessor.Request`.

- `tidb_paging_size_bytes` is allowed in `SET_VAR` hints; default 0
  disables byte-budget paging.
- The value flows through `DistSQLContext` into
  `kv.Request.Paging.PagingSizeBytes` via `RequestBuilder`.
- In the cop client, `pagingBytesEligible` gates the feature to
  TiKV + DAG requests. When the byte budget is positive on an
  eligible request whose row-count paging is disabled, paging is
  force-enabled with minimum row parameters so the byte budget
  becomes the dominant page-break signal. This must happen before
  `checkStoreBatchCopr` because batch copr is incompatible with
  paging.
- The byte budget is carried on each generated `copTask`,
  populates `coprocessor.Request.PagingSizeBytes` on outgoing
  RPCs, propagates onto retried tasks (region/lock errors), and
  is cleared together with `pagingSize` when the small-limit
  downgrade fires.

Dependency:

- Pin `pingcap/kvproto` to JmPotato/kvproto demo/ru-paging-size
  which adds `paging_size_bytes` (tag 17) to `coprocessor.Request`
  via pingcap/kvproto#1448; revert this replace once that PR is
  merged and tagged.

Tests:

- `TestPagingBytesEligible` covers eligibility for TiKV/DAG vs
  TiFlash and non-DAG requests.
- `TestBuildCopTasksWithPagingSizeBytes` covers task construction
  with and without small-limit downgrade.
- `tests/integrationtest/sessionctx/setvar` is extended to cover
  the new sysvar (default, set, set via SET_VAR hint).

Signed-off-by: JmPotato <github@ipotato.me>
JmPotato added a commit to JmPotato/tidb that referenced this pull request Jul 1, 2026
@JmPotato
*: add tidb_paging_size_bytes and forward it to coprocessor RPC
6c02b7c 
Add a TiDB-side knob `tidb_paging_size_bytes` (global+session sysvar,
default 0) and plumb the value end-to-end so it lands as the new
`paging_size_bytes` field on `coprocessor.Request`.

- `tidb_paging_size_bytes` is allowed in `SET_VAR` hints; default 0
  disables byte-budget paging.
- The value flows through `DistSQLContext` into
  `kv.Request.Paging.PagingSizeBytes` via `RequestBuilder`.
- In the cop client, `pagingBytesEligible` gates the feature to
  TiKV + DAG requests. When the byte budget is positive on an
  eligible request whose row-count paging is disabled, paging is
  force-enabled with minimum row parameters so the byte budget
  becomes the dominant page-break signal. This must happen before
  `checkStoreBatchCopr` because batch copr is incompatible with
  paging.
- The byte budget is carried on each generated `copTask`,
  populates `coprocessor.Request.PagingSizeBytes` on outgoing
  RPCs, propagates onto retried tasks (region/lock errors), and
  is cleared together with `pagingSize` when the small-limit
  downgrade fires.

Dependency:

- Pin `pingcap/kvproto` to JmPotato/kvproto demo/ru-paging-size
  which adds `paging_size_bytes` (tag 17) to `coprocessor.Request`
  via pingcap/kvproto#1448; revert this replace once that PR is
  merged and tagged.

Tests:

- `TestPagingBytesEligible` covers eligibility for TiKV/DAG vs
  TiFlash and non-DAG requests.
- `TestBuildCopTasksWithPagingSizeBytes` covers task construction
  with and without small-limit downgrade.
- `tests/integrationtest/sessionctx/setvar` is extended to cover
  the new sysvar (default, set, set via SET_VAR hint).

Signed-off-by: JmPotato <github@ipotato.me>
@JmPotato JmPotato mentioned this pull request Jul 1, 2026
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@cfzjywxk cfzjywxk cfzjywxk approved these changes
@lhy1024 lhy1024 lhy1024 approved these changes
@rleungx rleungx rleungx approved these changes
@fzzf678 fzzf678 Awaiting requested review from fzzf678
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