perf: migrate to unnest (from VALUES) for CTEs, INSERT .. SELECT FROM, SELECT/UPDATE FROM by jkaczman · Pull Request #2003 · pgdogdev/pgdog

jkaczman · 2026-11-09T21:21:48Z

Works off the previous changes implementing splitting INSERT with unnest (#1988, #2000) to now implement this unnest functionality to be used when re-writing subqueries (as opposed to re-writing the SQL to have an explicit VALUES clause with all the DataRows inlined) when we send the subquery data rows back to Postgres in the outer statement to be evaluated.

This should be a considerable speedup vs. before; if we had 10,000 DataRows returned, it's much cheaper to include the data in an array in a Bind parameter vs. creating a new SQL statement with 10,000 tuples and deparsing it.

Not handled for WHERE clause yet. Will follow up.

github-actions · 2026-11-09T21:40:40Z

Metal bench (arm64) failed. 1 of 475 measures outside bounds.

suite	throughput	cpu/txn	user cycles/txn	user instr/txn	kernel cycles/txn	kernel instr/txn	ctx/txn
pooler		18.73 (+0.7% ± 1.0%)	18,041 (+1.2% ± 0.2%)	32,046 (+0.1% ± 0.04%)	29,633 (+0.1% ± 1.8%)	51,184 (-0.2% ± 0.3%)
lb		19.34 (+1.1% ± 0.7%)	18,649 (+1.2% ± 0.5%)	32,939 (+0.0% ± 0.08%)	30,403 (+0.6% ± 1.0%)	52,351 (-0.1% ± 0.2%)
sharding-w2		33.98 (+1.4% ± 1.5%)	46,270 (+1.1% ± 2.7%)	97,433 (+0.0% ± 0.01%)	42,071 (+0.8% ± 4.1%)	53,681 (+0.0% ± 0.2%)	1.543 (+0.1% ± 0.1%)
sharding-w8	241,163 (+0.4% ± 0.6%)	29.81 (-0.5% ± 1.1%)	45,352 (-1.7% ± 2.8%)	52,975 (+0.0% ± 0.2%)	37,032 (+1.0% ± 2.9%)	42,364 (+0.0% ± 0.3%)	0.1654 (+1.7% ± 5.0%)

Counters per txn

suite	frontend stall	l1i refill
pooler	7,114 (-0.5% ± 0.9%)	2,563 (-0.1% ± 0.2%)
lb	7,433 (-0.0% ± 1.2%)	2,626 (+0.2% ± 0.5%)
sharding-w2	20,000 (+1.5% ± 8.1%)	4,310 (+0.2% ± 5.6%)
sharding-w8	20,835 (-6.1% ± 6.6%)	4,157 (-4.6% ± 3.8%)

benchmark	measure	result	baseline	change	bound
full_named_cached::min_max_sum	instructions	130,486	128,512	+1.54% ± 0.00%	+1%

Microbench: 461 of 462 measures within bounds.

Hot code per txn

path	base	head	change
pooler	109.1 KB	109.9 KB	+0.8 KB
sharding-w2	164.4 KB	163.9 KB	-0.6 KB

pooler:

crate	base	head	change
pgdog::frontend::client::query_engine	19.7 KB	19.8 KB	+0.1 KB
tokio	18.2 KB	18.6 KB	+0.3 KB
pgdog::backend::pool	17.4 KB	17.2 KB	-0.2 KB
aws-lc (TLS crypto)	10.2 KB	9.8 KB	-0.4 KB
rustls (TLS)	8.2 KB	8.4 KB	+0.1 KB
pgdog::frontend (other)	7.8 KB	7.8 KB	+0.0 KB
pgdog::backend::server	7.1 KB	7.3 KB	+0.2 KB
other	5.8 KB	6.2 KB	+0.5 KB
everything else	14.7 KB	14.9 KB	+0.2 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	5.4 KB	+0.0 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	5.4 KB	+0.0 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	4.1 KB	+0.0 KB
`tokio::runtime::task::raw::poll`	3.2 KB	+0.1 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	2.9 KB	+0.0 KB

sharding-w2:

crate	base	head	change
pgdog::frontend::router	28.5 KB	28.8 KB	+0.2 KB
pgdog::frontend::client::query_engine	21.1 KB	21.4 KB	+0.2 KB
tokio	19.0 KB	18.8 KB	-0.2 KB
pgdog::backend::pool	17.9 KB	18.2 KB	+0.2 KB
aws-lc (TLS crypto)	12.6 KB	12.2 KB	-0.3 KB
other	9.8 KB	9.5 KB	-0.2 KB
pgdog::frontend (other)	8.4 KB	8.6 KB	+0.2 KB
rustls (TLS)	8.2 KB	8.1 KB	-0.1 KB
everything else	38.9 KB	38.3 KB	-0.6 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	6.0 KB	+0.0 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	5.5 KB	+0.2 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	4.1 KB	+0.1 KB
`tokio::runtime::task::raw::poll`	3.4 KB	+0.2 KB
`pgdog::frontend::router::parser::query::select::<impl pgdog::frontend::router::parser::que`	3.4 KB	+0.0 KB

lb flamegraph vs 4bb1985

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microbench flamegraph vs 4bb1985

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pooler flamegraph vs 4bb1985

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sharding-w2 flamegraph vs 4bb1985

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sharding-w8 flamegraph vs 4bb1985

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Logs

lb, microbench, pooler, sharding-w2, sharding-w8, verdict.json

Compared b0a3b72 with 4bb1985 on m8g.metal-24xl (spot).

github-actions · 2026-11-09T21:41:48Z

Metal bench (x86) passed. All 475 measures within bounds.

suite	throughput	cpu/txn	user cycles/txn	user instr/txn	kernel cycles/txn	kernel instr/txn	ctx/txn
pooler		34.88 (+0.3% ± 0.3%)	23,065 (+1.2% ± 0.9%)	33,900 (+0.0% ± 0.02%)	58,148 (+0.1% ± 0.4%)	38,508 (-0.0% ± 0.1%)
lb		35.78 (+0.1% ± 0.2%)	24,123 (+0.8% ± 0.5%)	34,852 (+0.0% ± 0.03%)	58,847 (-0.3% ± 0.3%)	39,198 (-0.1% ± 0.2%)
sharding-w2		56.4 (-0.1% ± 0.5%)	52,924 (-0.5% ± 1.2%)	101,308 (+0.0% ± 0.01%)	72,885 (+0.0% ± 1.7%)	43,110 (+0.0% ± 0.1%)	1.394 (+0.0% ± 0.4%)
sharding-w8	147,976 (-0.4% ± 0.8%)	48.25 (+0.0% ± 0.5%)	58,441 (+0.6% ± 1.1%)	56,800 (+0.1% ± 0.03%)	64,040 (-0.4% ± 0.2%)	34,225 (+0.0% ± 0.2%)	0.1682 (-1.2% ± 1.0%)

Counters per txn

suite	frontend stall	l1i refill
pooler	75,591 (+4.3% ± 1.0%)	3,626 (+2.1% ± 0.2%)
lb	78,319 (+3.9% ± 1.2%)	3,743 (+1.7% ± 0.06%)
sharding-w2	155,227 (-0.1% ± 2.3%)	5,936 (-0.7% ± 0.4%)
sharding-w8	123,404 (+1.5% ± 0.5%)	4,873 (+1.1% ± 0.4%)

Microbench: all 462 measures within bounds.

Microbench latency: 1 benches changed more than 3%

benchmark	latency	baseline	change	instructions change
full_extended_cached::delete_all_shards	19,460 ns	18,364 ns	+5.97% ± 3.85%	+0.06% ± 0.00%

Hot code per txn

path	base	head	change
pooler	101.2 KB	105.4 KB	+4.1 KB
sharding-w2	158.4 KB	158.7 KB	+0.2 KB

pooler:

crate	base	head	change
pgdog::frontend::client::query_engine	19.3 KB	20.4 KB	+1.1 KB
tokio	17.6 KB	17.7 KB	+0.1 KB
pgdog::backend::pool	16.2 KB	16.6 KB	+0.4 KB
pgdog::frontend (other)	8.8 KB	9.1 KB	+0.3 KB
rustls (TLS)	7.1 KB	7.4 KB	+0.3 KB
aws-lc (TLS crypto)	7.1 KB	7.3 KB	+0.2 KB
pgdog::backend::server	5.7 KB	7.0 KB	+1.3 KB
other	5.6 KB	5.7 KB	+0.1 KB
everything else	13.9 KB	14.2 KB	+0.4 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	6.9 KB	+0.2 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	5.9 KB	+0.2 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	5.0 KB	+0.7 KB
`tokio::runtime::task::raw::poll`	3.8 KB	+0.2 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	3.1 KB	+0.1 KB

sharding-w2:

crate	base	head	change
pgdog::frontend::router	26.4 KB	27.3 KB	+0.9 KB
pgdog::frontend::client::query_engine	21.8 KB	22.2 KB	+0.4 KB
tokio	18.3 KB	18.1 KB	-0.2 KB
pgdog::backend::pool	17.6 KB	17.1 KB	-0.6 KB
other	10.0 KB	10.3 KB	+0.3 KB
aws-lc (TLS crypto)	10.1 KB	10.2 KB	+0.1 KB
pgdog::frontend (other)	10.0 KB	10.0 KB	+0.0 KB
rustls (TLS)	7.5 KB	7.4 KB	-0.1 KB
everything else	36.7 KB	36.1 KB	-0.6 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	7.5 KB	+0.0 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	6.1 KB	+0.0 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	4.9 KB	+0.2 KB
`pgdog::frontend::router::parser::query::select::<impl pgdog::frontend::router::parser::que`	4.1 KB	+0.1 KB
`tokio::runtime::task::raw::poll`	3.9 KB	+0.1 KB

lb flamegraph vs 4bb1985

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Open interactive.

microbench flamegraph vs 4bb1985

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Open interactive.

pooler flamegraph vs 4bb1985

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Open interactive.

sharding-w2 flamegraph vs 4bb1985

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Open interactive.

sharding-w8 flamegraph vs 4bb1985

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Logs

lb, microbench, pooler, sharding-w2, sharding-w8, verdict.json

Compared b0a3b72 with 4bb1985 on c7a.metal-48xl (spot).

codecov · 2026-11-09T22:07:15Z

Codecov Report

❌ Patch coverage is 87.40157% with 32 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog-postgres-types/src/datum.rs	35.00%	13 Missing ⚠️
pgdog/src/frontend/client/query_engine/query.rs	42.10%	11 Missing ⚠️
...end/client/query_engine/multi_step/subquery/mod.rs	90.47%	4 Missing ⚠️
...nt/query_engine/multi_step/subquery/from_clause.rs	99.00%	1 Missing ⚠️
.../query_engine/multi_step/subquery/insert_select.rs	88.88%	1 Missing ⚠️
...r/parser/rewrite/statement/subquery/from_clause.rs	90.90%	1 Missing ⚠️
...parser/rewrite/statement/subquery/insert_select.rs	92.85%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

… SELECT/UPDATE FROM

jkaczman added this pull request to stack #1986 November 9, 2026 21:21

jkaczman force-pushed the jk-subqueries-repl-values-w-unnest branch from b31ce78 to 3b31f94 Compare November 9, 2026 21:34

jkaczman force-pushed the jk-subqueries-repl-values-w-unnest branch 4 times, most recently from a7a706c to 422f97c Compare November 9, 2026 22:01

jkaczman force-pushed the jk-subqueries-repl-values-w-unnest branch 3 times, most recently from f3aac4a to dc61d2e Compare November 10, 2026 00:31

Base automatically changed from jk-unnest-select-targets to main November 10, 2026 02:12

jkaczman added 3 commits November 9, 2026 18:12

erf: migrate to unnest (from VALUES) for CTEs, INSERT .. SELECT FROM,…

9ff6768

… SELECT/UPDATE FROM

Clear compilation errors

0b52726

Revert change to always drop Parse/Bind

1524789

jkaczman force-pushed the jk-subqueries-repl-values-w-unnest branch from dc61d2e to 1524789 Compare November 10, 2026 02:12

jkaczman added 2 commits November 9, 2026 18:41

Fix clippy

2689791

restore FROM check

b0a3b72

jkaczman marked this pull request as ready for review November 10, 2026 03:20

jkaczman merged commit 81a9f08 into main Nov 10, 2026
46 of 47 checks passed

jkaczman deleted the jk-subqueries-repl-values-w-unnest branch November 10, 2026 12:14

This was referenced Nov 10, 2026

fix: in microbench, hash LRU caches with fixed seed #2008

Open

perf: migrate WHERE subqueries to unnest #2023

Open

perf: reference prior CTE data via unnest when evaluating later CTE #2024

Open

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perf: migrate to unnest (from VALUES) for CTEs, INSERT .. SELECT FROM, SELECT/UPDATE FROM - #2003

perf: migrate to unnest (from VALUES) for CTEs, INSERT .. SELECT FROM, SELECT/UPDATE FROM#2003
jkaczman merged 5 commits into
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