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Graph/unbounded-union-all-bloat

Pattern

Unbounded UNION Bloat

unbounded-union-all-bloat

A recurring query-shape where enumerating many columns/values via repeated UNION ALL (and related FROM/UNNEST constructs) leads to bloated SQL and long execution, and can be simplified by using scalar min/max functions or correct LATERAL UNNEST usage.

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Updated5/1/2026

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30 linked nodes

I can get the same performance issues with either a select or a delete — they join two tables, and none of the join conditions compares using `=`. Tension: `IS NOT DISTINCT FROM` is not supported by indexes, and `OR` is usually a performance problem anyway. Outcome: the root of your problem are the NULL values.

sqlc always generates a struct with an `interface — I’ve tried several approaches. Tension: I need to aggregate more complex data into a slice. Outcome: Composite and record types aren't yet supported by `sqlc`.

I want to keep these queries separate, but in the UI I want to consume them as one combined object — I have two separate queries using `@tanstack/angular-query`. Tension: I can't figure out how to combine the results like this. Outcome: Is there a built-in way in TanStack Query for Angular to derive/merge the results of two queries into one object.

ERROR: numeric field overflow. Tension: A field with precision 5, scale 1 must round to an absolute value less than 10^4. Outcome: ERROR: numeric field overflow.

got extra junk rows — SQLAlchemy filter on Query again. Outcome: simplify that down using joins and avoids having subqueries.

Athena is making separate calls to read footer, column data and separate calls to each partition if the file is large — using Athena to query an S3 bucket and using Athena partition projection as well. Tension: I use node, date and effective_time_start in query. Outcome: Apparently, this is how parquet works.

How can I write this using jOOQ version 3.15.5 ? — SELECT organisation_id, count((j->>'invoiceId')) AS count, sum((j->>'advanceAmount')::numeric(20,4)) AS sum FROM runs LEFT JOIN jsonb_array_elements(invoices) j on true GROUP BY organisation_id;.

Selecting a more optimal index for a PostgreSQL query that filters on multiple fields inside a JSONB column

ERROR: invalid memory alloc request size 1264582656 — CONTEXT: SQL function "st_transform_resilient" statement 1. Tension: No effect, no ERROR changes. Outcome: It seems lie your geometries are too large for the operation you want to perform.

all inserts fail with "multixact “members” limit exceeded (SQLSTATE 54000)". Tension: autovacuum may run for days and not complete in time.

none of the three queries you showed ended up using it — Select * from users where Type = 'SomeType' and First = 'SomeName1' Order by CreatedAt DESC;. Tension: The fact that you're selecting and ordering by `CreatedAt` doesn't mean it's needed as an index key. Outcome: If you simply remove `createdat` from the index, they're happy to use it for a Bitmap Index Scan taking below `5ms`.

table "location_array" has 1 columns available but 2 columns specified — FROM unnest(locations) AS location_array(lng, lat). Tension: trying to access slices - there's colon `:` syntax for that.

in which the query above is nested. Tension: why is it a must to alias in the second query and not the first ?

I want to calculate the average score of each row — removing one of the highest and one of the lowest scores. Tension: The following is the method I use. It is very bloated and the execution time is too long. Outcome: So I would like to ask if there is a neat way to achieve my needs?

The following is the method I use. It is very bloated and the execution time is too long. — especially if there are more score columns(score8, score9...), more `UNION ALL` will be piled up.

Hibernate send multiple statement in the same time and not merging them into multi-valued INSERT — When you set batch_size > 1. Tension: I was unable to find any official documentation on such INSERT statement merging. Outcome: it looks like this feature does exist and I just haven't quite managed to get it to work.

No built-in shorthand for null-safe addition in PostgreSQL

ERROR: missing FROM-clause entry for table cte — SELECT cte.type, t.* FROM UNNEST(cte.foos, cte.bars) AS t(foos, bars).

"too many range table entries" error — I'm trying to update a partitioned PostgreSQL table using a PL/pgsql loop. Tension: it contains a self join on a large table. Outcome: If I hardcode the partition to update in the WHERE clauses, it works just fine.

my goal is to get greatest value for each row — I use PostgreSQL and my goal is to get greatest value for each row. Tension: is there a way i can know which column these values are belong to? Outcome: Expected smth like: id greatest column.

Attempting to use UNNEST on multiple TEXT[] arrays to insert array elements as rows into a table results in misaligned values across columns. The inserted data ends up shifted (e.g., id/name/phone values come from different arrays).

Updating a jsonb column to remove specific keys (e.g., value1 and value2) for rows where a=1 does not delete the keys as expected using jsonb subtraction with multiple keys via VALUES/joins.

Cannot limit a domain value to at most two occurrences in a table

I see the expected results using above query. — Now I want to remove the entries from above result which are in table2. Tension: Is there a more efficient of achieving the same result? and are there any cases that I could be missing?

An INSERT...SELECT cron job is too slow because it aggregates 200K groups from data_time_series and conditionally inserts rows into storage_time_series using a NOT EXISTS subquery. The conditional existence check becomes a performance bottleneck.

How to translate an Excel named range (a collection of variant cell values) into a SQL representation so that functions like SUM can operate naturally over the range, ideally skipping values that don't make sense.

Create a PostgreSQL function/query that combines results of multiple aggregate queries (e.g., counts from different tables) into a single-row record.

more than one row returned by a subquery used as an expression.

Querying distinct counts of values inside a PostgreSQL text[] array column (actionServiceIds) with tenantId filtering becomes extremely slow as the permissions table grows (~100k rows). The approach requires unnesting and then grouping/distinct counting per id.

canceling statement due to statement timeout — the below query is timing out due to large data set. Tension: I appreciate any suggestions on how to increase the below query performance.

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