Every useful index also adds work to some writes. Wide update plans make that maintenance visible through separate index update operators and supporting sorts. The plan shape explains how SQL Server performs the work, not whether every index deserves to remain.
Identify Which Index Columns Change
Updating an indexed key or included column requires maintaining the affected index. Changing the clustered key can affect nonclustered indexes because it participates in their row locators. An UPDATE that changes an unindexed column has a different maintenance footprint.
I list the affected keys and included columns before comparing write plans. Counting indexes alone misses that distinction. An index useful to one query can still be expensive for frequent changes to its columns. The question is the balance across the workload, not whether index maintenance exists.
Use a disposable database with several indexes containing the changing Amount column. The sample is intentionally redundant enough to make maintenance visible. It is not an index design recommendation. SQL Server 2022 with compatibility level 160 supplies the generated input.
CREATE TABLE dbo.UpdateWidthDemo
(RowID int NOT NULL PRIMARY KEY,GroupID int NOT NULL,
StatusCode int NOT NULL,Amount decimal(12,2) NOT NULL);
INSERT dbo.UpdateWidthDemo
SELECT value,value%100,value%4,value%1000
FROM GENERATE_SERIES(1,3000000,1);
CREATE INDEX IX_UpdateWidthDemo_Amount ON dbo.UpdateWidthDemo(Amount);
CREATE INDEX IX_UpdateWidthDemo_Group ON dbo.UpdateWidthDemo(GroupID)
INCLUDE(Amount);
CREATE INDEX IX_UpdateWidthDemo_Status ON dbo.UpdateWidthDemo(StatusCode,Amount);Push Large Updates Into Wide Update Plans
Enable actual plans and use transactions that roll back the test changes. A small qualifying set can favor a narrow per-row maintenance plan. A larger set can favor separate per-index operations. The optimizer chooses the implementation from costs and eligibility, so the demonstration cannot guarantee a switch at one fixed row count.
SET STATISTICS IO ON;
BEGIN TRANSACTION;
UPDATE dbo.UpdateWidthDemo SET Amount=Amount+1 WHERE RowID<=10;
ROLLBACK TRANSACTION;
BEGIN TRANSACTION;
UPDATE dbo.UpdateWidthDemo SET Amount=Amount+1 WHERE RowID<=300000;
ROLLBACK TRANSACTION;
SET STATISTICS IO OFF;Inspect the changed-row estimates and actual counts. Compare the update operators, sorts, and index identities. If both statements use the same maintenance shape, report that observation rather than claiming the expected split occurred. Input estimates and index layout influence the choice.
On my SQL Server 2025 test instance, the 10-row update used one Clustered Index Update that maintained every index. The 300,000-row update switched to a wide plan with a Sort and an Index Update for each nonclustered index. With only 1,000,000 rows in the table, that same update stayed narrow, which is why the sample loads three million rows.
Rollback preserves the sample values, but it also performs work and can affect operational counters. Keep it outside the timed portion when your client supports that separation. The controlled exercise explains operators; production measurement needs a realistic successful transaction.
Read Narrow Plans Beside Wide Update Plans
A narrow update can maintain the relevant structures as rows flow through a combined update path. A wide plan separates work for individual indexes. Sorts can arrange rows in an index's key order before its update operator, improving access locality at the cost of sorting.
That extra sort is not automatically wasted work. The optimizer compares it with other ways of maintaining the affected indexes. A memory grant or spill can make the chosen shape more expensive, so inspect actual execution details rather than judging by operator count.
The number of qualifying rows matters because maintenance strategies have different fixed and per-row costs. Statistics and predicates therefore influence the write plan too. A bad estimate can affect sorts and grants even when the UPDATE's business logic is straightforward.
Do Not Read Table IO as Per-Index IO
STATISTICS IO reports table and internal-worktable activity. It does not provide a reliable separate line for every index maintained on one table. Naming an index in the execution plan does not change that reporting grain. Do not assign the table's reads independently to every index.
Use operational statistics for per-index activity clues. Capture a baseline before the controlled update and compare with a second capture while the transaction is still open. Aggregate partitions by object and index for this table. Counter lifetimes remain limited and concurrent work can affect the result.
SELECT index_id,SUM(leaf_update_count) AS LeafUpdates,
SUM(leaf_insert_count) AS LeafInserts,SUM(leaf_delete_count) AS LeafDeletes
INTO #IndexBefore
FROM sys.dm_db_index_operational_stats
(DB_ID(),OBJECT_ID(N'dbo.UpdateWidthDemo'),NULL,NULL)
GROUP BY index_id;
BEGIN TRANSACTION;
UPDATE dbo.UpdateWidthDemo SET Amount=Amount+1 WHERE RowID<=10000;
WITH AfterCounts AS
(
SELECT index_id,SUM(leaf_update_count) AS LeafUpdates,
SUM(leaf_insert_count) AS LeafInserts,SUM(leaf_delete_count) AS LeafDeletes
FROM sys.dm_db_index_operational_stats
(DB_ID(),OBJECT_ID(N'dbo.UpdateWidthDemo'),NULL,NULL)
GROUP BY index_id
)
SELECT i.name,a.LeafUpdates-b.LeafUpdates AS LeafUpdateDelta,
a.LeafInserts-b.LeafInserts AS LeafInsertDelta,
a.LeafDeletes-b.LeafDeletes AS LeafDeleteDelta
FROM AfterCounts a JOIN #IndexBefore b ON b.index_id=a.index_id
JOIN sys.indexes i ON i.object_id=OBJECT_ID(N'dbo.UpdateWidthDemo')
AND i.index_id=a.index_id;
ROLLBACK TRANSACTION;Interpret Counter Deltas Conservatively
An index-key change can involve delete and insert work rather than only leaf_update_count. Read those counters together. They are operation counts, not a stopwatch or exact byte total. A zero leaf-update delta does not prove an index had no maintenance cost. In my run, only the clustered index showed leaf updates. Each nonclustered index showed insert and delete counts instead.
Counters can reset when metadata cache entries disappear, when structures change, or after restart. Record capture times and check for negative or inconsistent deltas. Do not treat a reset as a performance improvement. Keep the test isolated when attributing counters to one statement.
I use these deltas to explain the plan, not to rank indexes by one number. Which structures changed, and how does their maintenance match the columns updated? The answer should agree with index definitions and actual operators before it informs a schema decision.
Review Read Benefits Before Removing Indexes
An apparently unused index can serve a monthly report or a critical rare lookup. Usage counters have reset and observation-window limits too. Retain a representative workload history before proposing removal. A short quiet interval cannot establish that an index has no purpose.
Compare overlapping definitions and their returned-column needs. Consolidating two indexes can reduce write cost, but the larger replacement can increase read and storage cost. Unique indexes and constraints also enforce correctness and cannot be evaluated only as query accelerators.
Any production removal needs approval, a preserved definition, and a rollback plan. This article changes no real index automatically. The sample's redundancy explains maintenance; it does not create a universal list of indexes to delete.
Measure Wide Update Plans Across the Write Workload
Include duration, CPU, logical reads, log growth, and blocking behavior under representative concurrency. A faster isolated update can still hold locks long enough to hurt application response time. Keep transaction size and caller behavior in the comparison.
Do not force narrow or wide shapes through undocumented settings. Improve supported inputs: accurate estimates, appropriate indexes, clear predicates, and justified batch sizing. The optimizer remains responsible for selecting the physical maintenance plan.
An extra index is a shelf that needs updating whenever its contents change. Keep shelves that earn their maintenance cost and reconsider those that do not. The evidence comes from the complete read and write workload, not the visual complexity of one UPDATE plan.
Keep sample updates away from the clustered identifier when first studying maintenance. That avoids combining ordinary indexed-value changes with locator changes. After understanding the simpler case, review clustered-key updates separately if the application performs them. Their wider maintenance footprint deserves its own evidence.
Wide update plans expose the index-specific maintenance paths selected for the statement. Compare the full write workload before treating wide update plans as a reason to change index definitions.
Related reading on this blog: Your Index Rebuild Maintenance Plan Is Rebuilding Indexes Nobody Uses and Identify Read Heavy Workload or Write Heavy Workload Type by Counters.
A wide update plan is not proof of a bad optimizer choice, it is visible index-maintenance work that needs a workload-level justification.
Published by Pinal Dave on SQLAuthority. More of my work at pinaldave.com.
