alamb commented on code in PR #8117:
URL: https://github.com/apache/arrow-datafusion/pull/8117#discussion_r1391532651
##########
docs/source/user-guide/sql/scalar_functions.md:
##########
@@ -1120,6 +1121,21 @@ Returns UUID v4 string value which is unique per row.
uuid()
```
+### `overlay`
+
+Returns the string which is replaced by another string from the specified
position and specified count length
+
+```
+overlay(str PLACING substr FROM pos [FOR count])
+```
+
Review Comment:
Having the example made it much easier for me to see what was going on in
postgres. Can we add an example here as well?
```suggestion
For example, `overlay('Txxxxas' placing 'hom' from 2 for 4) → Thomas`
```
##########
datafusion/sqllogictest/test_files/functions.slt:
##########
@@ -815,3 +815,33 @@ SELECT products.* REPLACE (price*2 AS price,
product_id+1000 AS product_id) FROM
1002 OldBrand Product 2 59.98
1003 OldBrand Product 3 79.98
1004 OldBrand Product 4 99.98
+
+#overlay tests
+statement ok
+CREATE TABLE over_test(
+ str TEXT,
+ characters TEXT,
+ pos INT,
+ len INT
+) as VALUES
+ ('123', 'abc', 4, 5),
+ ('abcdefg', 'qwertyasdfg', 1, 7),
+ ('xyz', 'ijk', 1, 2),
+ ('Txxxxas', 'hom', 2, 4)
Review Comment:
Can you please also test `NULL` handling here? I think your code handles it
properly, but it would be good to have this in the SQL tests. We can do this as
a follow on PR if you prefer.
Specifically
```suggestion
('Txxxxas', 'hom', 2, 4),
(NULL, 'hom', 2, 4), -- expect NULL output
('Txxxxas', 'hom', NULL, 4), -- expect NULL output
('Txxxxas', 'hom', 2, NULL) -- expect NULL output
```
##########
docs/source/user-guide/sql/scalar_functions.md:
##########
@@ -1120,6 +1121,21 @@ Returns UUID v4 string value which is unique per row.
uuid()
```
+### `overlay`
+
+Returns the string which is replaced by another string from the specified
position and specified count length
+
+```
+overlay(str PLACING substr FROM pos [FOR count])
+```
+
Review Comment:
Having the example made it much easier for me to see what was going on in
postgres. Can we add an example here as well?
```suggestion
For example, `overlay('Txxxxas' placing 'hom' from 2 for 4) → Thomas`
```
##########
docs/source/user-guide/sql/scalar_functions.md:
##########
@@ -1120,6 +1121,21 @@ Returns UUID v4 string value which is unique per row.
uuid()
```
+### `overlay`
+
+Returns the string which is replaced by another string from the specified
position and specified count length
+
+```
+overlay(str PLACING substr FROM pos [FOR count])
+```
+
+#### Arguments
+
+- **str**: String expression to operate on.
+- **substr**: the string to replace part of str.
+- **pos**: the start position to replace of str.
+- **count**: the count of characters to be replaced from start position of
str.If not specified, will use substr length instead.
Review Comment:
```suggestion
- **count**: the count of characters to be replaced from start position of
str. If not specified, will use substr length instead.
```
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