Add Unable To Infer Data Type In Production as a Postgres TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1578 TILs and counting..._
+_1579 TILs and counting..._
 
 See some of the other learning resources I work on:
 - [Ruby Operator Lookup](https://www.visualmode.dev/ruby-operators)
@@ -905,6 +905,7 @@ See some of the other learning resources I work on:
 - [Two Ways To Compute Factorial](postgres/two-ways-to-compute-factorial.md)
 - [Two Ways To Escape A Quote In A String](postgres/two-ways-to-escape-a-quote-in-a-string.md)
 - [Types By Category](postgres/types-by-category.md)
+- [Unable To Infer Data Type In Production](postgres/unable-to-infer-data-type-in-production.md)
 - [Union All Rows Including Duplicates](postgres/union-all-rows-including-duplicates.md)
 - [Use A psqlrc File For Common Settings](postgres/use-a-psqlrc-file-for-common-settings.md)
 - [Use A Trigger To Mirror Inserts To Another Table](postgres/use-a-trigger-to-mirror-inserts-to-another-table.md)

postgres/unable-to-infer-data-type-in-production.md

@@ -0,0 +1,45 @@
+# Unable To Infer Data Type In Production
+
+Inspired by [You Probably Don't Need Query
+Builders](https://mattrighetti.com/2025/01/20/you-dont-need-sql-builders), I
+wrote a query in one of my applications that has filter clauses that get
+short-circuited if the filter value hasn't been included.
+
+That query looked something like this:
+
+```ruby
+@tags =
+  Tag.where("? is null or normalized_value ilike ?", normalized_query, "%#{normalized_query}%")
+     .order(:normalized_value)
+     .limit(10)
+```
+
+The `normalized_value ilike ?` filtering won't be applied if the
+`normalized_query` value isn't present (`nil`). This helps me avoid writing
+messy ternaries or if-else conditional query building madness.
+
+Unfortunately, when I shipped this query to production, the page started
+failing and Postgres was reporting this error in the logs.
+
+```
+Caused by: PG::IndeterminateDatatype (ERROR:  could not determine data type of parameter $1)
+```
+
+The query is prepared as a parameterized statement and Postgres appears to be
+unable to determine the datatype of the first parameter (`$1`) —
+`normalized_query`.
+
+I was unable to reproduce the issue in development. It was only occuring in
+production. Until I can come up with a root cause analysis, I have the
+following fix that does a casting to `text`. This helps out with the type
+inference and makes the issue go away.
+
+```ruby
+@tags =
+  Tag.where("cast(? as text) is null or normalized_value ilike ?", normalized_query, "%#{normalized_query}%")
+     .order(:normalized_value)
+     .limit(10)
+```
+
+Interestingly, this person using `pgtyped` [ran into the exact same issue with
+the same type of query](https://github.com/adelsz/pgtyped/issues/354).