docs: Fix some broken / missing links in the DataFusion documentation (#19958)

## Which issue does this PR close?



## Rationale for this change

While reading the DataFusion documentation, I noticed a broken link
here:



<img width="787" height="885" alt="Screenshot 2026-01-23 at 9 34 43 AM"
src="https://github.com/user-attachments/assets/9013151d-599b-4973-968e-0033c6614643"
/>


## What changes are included in this PR?

Fix several broken and missing links (this was done by codex and I
reviewed the PR)

## Are these changes tested?

Yes, by CI
## Are there any user-facing changes?
Better docs. No functional changes intended

Author: alamb

datafusion/functions/src/datetime/to_timestamp.rs

@@ -42,7 +42,8 @@ use datafusion_macros::user_doc;
     description = r#"
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided. 
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -96,7 +97,8 @@ pub struct ToTimestampFunc {
     description = r#"
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided. 
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -145,7 +147,8 @@ pub struct ToTimestampSecondsFunc {
     description = r#"
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided. 
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as milliseconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -194,7 +197,8 @@ pub struct ToTimestampMillisFunc {
     description = r#"
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided. 
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as microseconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -243,7 +247,8 @@ pub struct ToTimestampMicrosFunc {
     description = r#"
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000000000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided. 
+Strings that parse without a time zone are treated as if they are in the
 session time zone. Integers, unsigned integers, and doubles are interpreted as nanoseconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
 The session time zone can be set using the statement `SET TIMEZONE = 'desired time zone'`.

datafusion/functions/src/datetime/to_unixtime.rs

@@ -27,7 +27,12 @@ use std::any::Any;
 
 #[user_doc(
     doc_section(label = "Time and Date Functions"),
-    description = "Converts a value to seconds since the unix epoch (`1970-01-01T00:00:00`). Supports strings, dates, timestamps, integer, unsigned integer, and float types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00') if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided. Integers, unsigned integers, and floats are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00`).",
+    description = r#"
+Converts a value to seconds since the unix epoch (`1970-01-01T00:00:00`).
+Supports strings, dates, timestamps, integer, unsigned integer, and float types as input.
+Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided.
+Integers, unsigned integers, and floats are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00`)."#,
     syntax_example = "to_unixtime(expression[, ..., format_n])",
     sql_example = r#"
 ```sql

docs/source/contributor-guide/testing.md

@@ -104,6 +104,7 @@ locally by following the [instructions in the documentation].
 
 [sqlite test suite]: https://www.sqlite.org/sqllogictest/dir?ci=tip
 [instructions in the documentation]: https://github.com/apache/datafusion/tree/main/datafusion/sqllogictest#running-tests-sqlite
+[extended.yml]: https://github.com/apache/datafusion/blob/main/.github/workflows/extended.yml
 
 ## Rust Integration Tests
 

docs/source/library-user-guide/query-optimizer.md

@@ -514,3 +514,5 @@ fn analyze_filter_example() -> Result<()> {
     Ok(())
 }
 ```
+
+[treenode api]: https://docs.rs/datafusion/latest/datafusion/common/tree_node/trait.TreeNode.html

docs/source/user-guide/arrow-introduction.md

@@ -220,6 +220,7 @@ When working with Arrow and RecordBatches, watch out for these common issues:
 - [Schema](https://docs.rs/arrow-schema/latest/arrow_schema/struct.Schema.html) - Describes the structure of a RecordBatch (column names and types)
 
 [apache arrow]: https://arrow.apache.org/docs/index.html
+[arrow-rs]: https://github.com/apache/arrow-rs
 [`arc`]: https://doc.rust-lang.org/std/sync/struct.Arc.html
 [`arrayref`]: https://docs.rs/arrow-array/latest/arrow_array/array/type.ArrayRef.html
 [`cast`]: https://docs.rs/arrow/latest/arrow/compute/fn.cast.html

docs/source/user-guide/crate-configuration.md

@@ -24,6 +24,7 @@ your Rust project. The [Configuration Settings] section lists options that
 control additional aspects DataFusion's runtime behavior.
 
 [configuration settings]: configs.md
+[support for adding dependencies]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-dependencies
 
 ## Using the nightly DataFusion builds
 

docs/source/user-guide/sql/scalar_functions.md

@@ -2880,7 +2880,8 @@ Additional examples can be found [here](https://github.com/apache/datafusion/blo
 
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided.
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -2928,7 +2929,8 @@ Additional examples can be found [here](https://github.com/apache/datafusion/blo
 
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided.
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as microseconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -2971,7 +2973,8 @@ Additional examples can be found [here](https://github.com/apache/datafusion/blo
 
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided.
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as milliseconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -3014,7 +3017,8 @@ Additional examples can be found [here](https://github.com/apache/datafusion/blo
 
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00.000000000<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided.
+Strings that parse without a time zone are treated as if they are in the
 session time zone. Integers, unsigned integers, and doubles are interpreted as nanoseconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
 The session time zone can be set using the statement `SET TIMEZONE = 'desired time zone'`.
@@ -3056,7 +3060,8 @@ Additional examples can be found [here](https://github.com/apache/datafusion/blo
 
 Converts a value to a timestamp (`YYYY-MM-DDT00:00:00<TZ>`) in the session time zone. Supports strings,
 integer, unsigned integer, and double types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
-if no [Chrono formats] are provided. Strings that parse without a time zone are treated as if they are in the
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided.
+Strings that parse without a time zone are treated as if they are in the
 session time zone, or UTC if no session time zone is set.
 Integers, unsigned integers, and doubles are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00Z`).
 
@@ -3097,7 +3102,11 @@ Additional examples can be found [here](https://github.com/apache/datafusion/blo
 
 ### `to_unixtime`
 
-Converts a value to seconds since the unix epoch (`1970-01-01T00:00:00`). Supports strings, dates, timestamps, integer, unsigned integer, and float types as input. Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00') if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided. Integers, unsigned integers, and floats are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00`).
+Converts a value to seconds since the unix epoch (`1970-01-01T00:00:00`).
+Supports strings, dates, timestamps, integer, unsigned integer, and float types as input.
+Strings are parsed as RFC3339 (e.g. '2023-07-20T05:44:00')
+if no [Chrono formats](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) are provided.
+Integers, unsigned integers, and floats are interpreted as seconds since the unix epoch (`1970-01-01T00:00:00`).
 
 ```sql
 to_unixtime(expression[, ..., format_n])