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		18.66 (+0.5% ± 0.5%)	18,010 (+0.9% ± 0.2%)	32,033 (+0.0% ± 0.05%)	29,541 (+0.2% ± 0.7%)	51,220 (-0.1% ± 0.6%)
lb		19.38 (+0.9% ± 0.8%)	18,603 (+1.2% ± 0.2%)	32,931 (+0.0% ± 0.04%)	30,577 (+0.4% ± 1.4%)	52,285 (-0.3% ± 0.3%)
sharding-w2		33.8 (+1.4% ± 0.4%)	46,143 (+1.4% ± 2.0%)	97,463 (+0.1% ± 0.08%)	41,933 (+1.0% ± 1.3%)	53,565 (-0.0% ± 0.06%)	1.539 (-0.1% ± 0.3%)
sharding-w8	241,425 (-0.6% ± 1.2%)	29.77 (+0.5% ± 1.2%)	45,637 (+0.3% ± 1.1%)	52,979 (+0.1% ± 0.02%)	36,642 (+0.7% ± 2.0%)	42,387 (+0.0% ± 0.03%)	0.1651 (+1.1% ± 2.1%)

Counters per txn

suite	frontend stall	l1i refill
pooler	7,170 (+0.4% ± 0.5%)	2,585 (+0.2% ± 0.3%)
lb	7,476 (+1.0% ± 0.9%)	2,640 (+0.6% ± 0.2%)
sharding-w2	19,842 (+2.6% ± 6.7%)	4,290 (+0.5% ± 4.6%)
sharding-w8	21,162 (-1.4% ± 2.7%)	4,201 (-1.0% ± 1.1%)

benchmark	measure	result	baseline	change	bound
full_simple::aggregate	instructions	148,635	147,114	+1.03% ± 0.00%	+1%

Microbench: 461 of 462 measures within bounds.

Hot code per txn

path	base	head	change
pooler	111.2 KB	111.8 KB	+0.6 KB
sharding-w2	166.2 KB	165.0 KB	-1.2 KB

pooler:

crate	base	head	change
pgdog::frontend::client::query_engine	19.8 KB	19.7 KB	-0.1 KB
tokio	18.4 KB	18.2 KB	-0.1 KB
pgdog::backend::pool	17.4 KB	17.4 KB	+0.0 KB
aws-lc (TLS crypto)	10.2 KB	10.4 KB	+0.2 KB
rustls (TLS)	8.4 KB	8.5 KB	+0.1 KB
pgdog::frontend (other)	7.8 KB	7.9 KB	+0.1 KB
pgdog::backend::server	7.2 KB	7.1 KB	-0.1 KB
other	6.4 KB	6.6 KB	+0.2 KB
everything else	15.8 KB	16.0 KB	+0.2 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	5.5 KB	+0.2 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	5.3 KB	-0.1 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	4.0 KB	-0.1 KB
`tokio::runtime::task::raw::poll`	3.2 KB	+0.0 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	28.7 KB	29.2 KB	+0.6 KB
pgdog::frontend::client::query_engine	21.2 KB	21.2 KB	+0.0 KB
tokio	18.6 KB	18.4 KB	-0.2 KB
pgdog::backend::pool	18.2 KB	18.1 KB	-0.1 KB
aws-lc (TLS crypto)	12.9 KB	12.9 KB	-0.1 KB
other	9.9 KB	9.9 KB	+0.1 KB
pgdog::frontend (other)	8.5 KB	8.6 KB	+0.1 KB
rustls (TLS)	8.1 KB	8.1 KB	-0.1 KB
everything else	40.1 KB	38.5 KB	-1.6 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	6.2 KB	+0.2 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	5.4 KB	-0.1 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	4.2 KB	+0.0 KB
`pgdog::frontend::router::parser::query::select::<impl pgdog::frontend::router::parser::que`	3.4 KB	+0.1 KB
`tokio::runtime::task::raw::poll`	3.1 KB	-0.1 KB

lb flamegraph vs df1af3b

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Open interactive.

microbench flamegraph vs df1af3b

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Open interactive.

pooler flamegraph vs df1af3b

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Open interactive.

sharding-w2 flamegraph vs df1af3b

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sharding-w8 flamegraph vs df1af3b

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Logs

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

Compared 6109875 with df1af3b on m8g.metal-24xl (spot).

github-actions · 2026-11-09T21:41:48Z

Metal bench (x86) 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		34.63 (-1.3% ± 0.2%)	22,685 (-4.5% ± 0.4%)	33,903 (+0.1% ± 0.02%)	57,782 (-0.3% ± 0.4%)	38,549 (+0.2% ± 0.05%)
lb		35.63 (-1.5% ± 0.2%)	23,884 (-5.2% ± 0.6%)	34,856 (+0.1% ± 0.03%)	58,642 (-0.4% ± 0.2%)	39,227 (+0.2% ± 0.08%)
sharding-w2		56.22 (-1.1% ± 0.5%)	52,677 (-2.8% ± 1.4%)	101,330 (+0.0% ± 0.07%)	72,774 (-0.3% ± 0.3%)	43,116 (+0.1% ± 0.1%)	1.395 (+0.3% ± 0.10%)
sharding-w8	148,442 (-0.1% ± 1.5%)	48.36 (+0.2% ± 1.0%)	58,648 (+0.2% ± 1.6%)	56,780 (+0.0% ± 0.07%)	64,176 (+0.3% ± 0.6%)	34,195 (+0.0% ± 0.2%)	0.1658 (-0.4% ± 2.5%)

Counters per txn

suite	frontend stall	l1i refill
pooler	72,742 (-9.0% ± 0.7%)	3,564 (-3.2% ± 0.1%)
lb	75,835 (-10.1% ± 0.8%)	3,684 (-3.6% ± 0.3%)
sharding-w2	153,843 (-4.6% ± 2.3%)	5,929 (-0.9% ± 0.9%)
sharding-w8	123,308 (-2.4% ± 1.1%)	4,790 (-0.6% ± 0.9%)

benchmark	measure	result	baseline	change	bound
full_named_cached::aggregate	instructions	146,308	144,637	+1.16% ± 0.00%	+1%

Microbench: 461 of 462 measures within bounds.

Microbench latency: 4 benches changed more than 3%

benchmark	latency	baseline	change	instructions change
simple_cold::set	2,462 ns	2,586 ns	-4.78% ± 2.18%	+0.00% ± 0.00%
simple_cold::begin	1,948 ns	2,032 ns	-4.13% ± 1.53%	+0.00% ± 0.00%
simple_cold::update_by_key	4,314 ns	4,473 ns	-3.54% ± 2.04%	+0.00% ± 0.00%
simple_cold::update_all_shards	3,452 ns	3,565 ns	-3.16% ± 1.26%	+0.00% ± 0.00%

Hot code per txn

path	base	head	change
pooler	103.6 KB	104.3 KB	+0.7 KB
sharding-w2	158.4 KB	157.8 KB	-0.6 KB

pooler:

crate	base	head	change
pgdog::frontend::client::query_engine	19.8 KB	20.0 KB	+0.2 KB
tokio	17.6 KB	17.8 KB	+0.2 KB
pgdog::backend::pool	16.7 KB	16.6 KB	-0.1 KB
pgdog::frontend (other)	8.9 KB	8.9 KB	-0.1 KB
aws-lc (TLS crypto)	7.2 KB	7.4 KB	+0.1 KB
rustls (TLS)	7.7 KB	7.2 KB	-0.5 KB
pgdog::backend::server	6.0 KB	6.6 KB	+0.6 KB
other	5.9 KB	5.6 KB	-0.4 KB
everything else	13.8 KB	14.3 KB	+0.5 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	6.7 KB	-0.1 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	6.0 KB	+0.2 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	4.7 KB	+0.1 KB
`tokio::runtime::task::raw::poll`	3.6 KB	+0.1 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	3.0 KB	-0.1 KB

sharding-w2:

crate	base	head	change
pgdog::frontend::router	26.8 KB	26.6 KB	-0.1 KB
pgdog::frontend::client::query_engine	22.2 KB	21.8 KB	-0.4 KB
tokio	17.8 KB	17.8 KB	+0.1 KB
pgdog::backend::pool	17.6 KB	17.3 KB	-0.3 KB
aws-lc (TLS crypto)	10.5 KB	10.4 KB	-0.1 KB
pgdog::frontend (other)	10.0 KB	10.1 KB	+0.1 KB
other	10.1 KB	9.9 KB	-0.2 KB
rustls (TLS)	7.7 KB	7.4 KB	-0.2 KB
everything else	35.8 KB	36.3 KB	+0.6 KB

function	head	change
`pgdog::frontend::client::Client::run::{{closure}}`	7.6 KB	+0.1 KB
`pgdog::frontend::client::query_engine::query::<impl pgdog::frontend::client::query_engine:`	5.9 KB	+0.1 KB
`pgdog::frontend::client::query_engine::QueryEngine::handle::{{closure}}`	4.8 KB	-0.2 KB
`pgdog::frontend::router::parser::query::select::<impl pgdog::frontend::router::parser::que`	3.9 KB	+0.0 KB
`tokio::runtime::task::raw::poll`	3.7 KB	-0.1 KB

lb flamegraph vs df1af3b

Open interactive for hover, zoom and search.

Open interactive.

microbench flamegraph vs df1af3b

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Open interactive.

pooler flamegraph vs df1af3b

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Open interactive.

sharding-w2 flamegraph vs df1af3b

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Open interactive.

sharding-w8 flamegraph vs df1af3b

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Open interactive.

Logs

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

Compared 6109875 with df1af3b on c7a.metal-48xl (spot).

codecov · 2026-11-09T22:07:15Z

Codecov Report

❌ Patch coverage is 87.74704% with 31 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 ⚠️

📢 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 from 6109875 to 5728343 Compare November 9, 2026 23:50

jkaczman added 3 commits November 9, 2026 15:52

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

3d559ad

… SELECT/UPDATE FROM

Clear compilation errors

a08ed26

Revert change to always drop Parse/Bind

f3aac4a

jkaczman force-pushed the jk-subqueries-repl-values-w-unnest branch from 5728343 to f3aac4a Compare November 9, 2026 23:52

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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
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