Merge #38863

38863: sql: fix substring builtin documentation r=nvanbenschoten a=nvanbenschoten

The docs were claiming that the third (optional) arg for the substring
builtin was an end position, but it's actually (correctly) a length.
This commit fixes that.

Release note: None

Co-authored-by: Nathan VanBenschoten <nvanbenschoten@gmail.com>

docs/generated/sql/functions.md

@@ -911,17 +911,17 @@ has no relationship with the commit order of concurrent transactions.</p>
 </span></td></tr>
 <tr><td><code>substr(input: <a href="string.html">string</a>, regex: <a href="string.html">string</a>, escape_char: <a href="string.html">string</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> that matches the regular expression <code>regex</code> using <code>escape_char</code> as your escape character instead of <code>\</code>.</p>
 </span></td></tr>
-<tr><td><code>substr(input: <a href="string.html">string</a>, start_pos: <a href="int.html">int</a>, end_pos: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> between <code>start_pos</code> and <code>end_pos</code> (count starts at 1).</p>
+<tr><td><code>substr(input: <a href="string.html">string</a>, start_pos: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> starting at <code>start_pos</code> (count starts at 1).</p>
 </span></td></tr>
-<tr><td><code>substr(input: <a href="string.html">string</a>, substr_pos: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> starting at <code>substr_pos</code> (count starts at 1).</p>
+<tr><td><code>substr(input: <a href="string.html">string</a>, start_pos: <a href="int.html">int</a>, length: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> starting at <code>start_pos</code> (count starts at 1) and including up to <code>length</code> characters.</p>
 </span></td></tr>
 <tr><td><code>substring(input: <a href="string.html">string</a>, regex: <a href="string.html">string</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> that matches the regular expression <code>regex</code>.</p>
 </span></td></tr>
 <tr><td><code>substring(input: <a href="string.html">string</a>, regex: <a href="string.html">string</a>, escape_char: <a href="string.html">string</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> that matches the regular expression <code>regex</code> using <code>escape_char</code> as your escape character instead of <code>\</code>.</p>
 </span></td></tr>
-<tr><td><code>substring(input: <a href="string.html">string</a>, start_pos: <a href="int.html">int</a>, end_pos: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> between <code>start_pos</code> and <code>end_pos</code> (count starts at 1).</p>
+<tr><td><code>substring(input: <a href="string.html">string</a>, start_pos: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> starting at <code>start_pos</code> (count starts at 1).</p>
 </span></td></tr>
-<tr><td><code>substring(input: <a href="string.html">string</a>, substr_pos: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> starting at <code>substr_pos</code> (count starts at 1).</p>
+<tr><td><code>substring(input: <a href="string.html">string</a>, start_pos: <a href="int.html">int</a>, length: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns a substring of <code>input</code> starting at <code>start_pos</code> (count starts at 1) and including up to <code>length</code> characters.</p>
 </span></td></tr>
 <tr><td><code>to_english(val: <a href="int.html">int</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>This function enunciates the value of its argument using English cardinals.</p>
 </span></td></tr>

pkg/sql/sem/builtins/builtins.go

@@ -3093,7 +3093,7 @@ var substringImpls = makeBuiltin(tree.FunctionProperties{Category: categoryStrin
 	tree.Overload{
 		Types: tree.ArgTypes{
 			{"input", types.String},
-			{"substr_pos", types.Int},
+			{"start_pos", types.Int},
 		},
 		ReturnType: tree.FixedReturnType(types.String),
 		Fn: func(_ *tree.EvalContext, args tree.Datums) (tree.Datum, error) {
@@ -3109,13 +3109,13 @@ var substringImpls = makeBuiltin(tree.FunctionProperties{Category: categoryStrin
 
 			return tree.NewDString(string(runes[start:])), nil
 		},
-		Info: "Returns a substring of `input` starting at `substr_pos` (count starts at 1).",
+		Info: "Returns a substring of `input` starting at `start_pos` (count starts at 1).",
 	},
 	tree.Overload{
 		Types: tree.ArgTypes{
 			{"input", types.String},
 			{"start_pos", types.Int},
-			{"end_pos", types.Int},
+			{"length", types.Int},
 		},
 		ReturnType: tree.FixedReturnType(types.String),
 		Fn: func(_ *tree.EvalContext, args tree.Datums) (tree.Datum, error) {
@@ -3147,7 +3147,8 @@ var substringImpls = makeBuiltin(tree.FunctionProperties{Category: categoryStrin
 
 			return tree.NewDString(string(runes[start:end])), nil
 		},
-		Info: "Returns a substring of `input` between `start_pos` and `end_pos` (count starts at 1).",
+		Info: "Returns a substring of `input` starting at `start_pos` (count starts at 1) and " +
+			"including up to `length` characters.",
 	},
 	tree.Overload{
 		Types: tree.ArgTypes{