add support for text database functions

Author: timgraham

.github/workflows/test-python.yml

@@ -77,6 +77,7 @@ jobs:
           db_functions.comparison
           db_functions.datetime
           db_functions.math
+          db_functions.text
           empty
           defer
           defer_regress

README.md

@@ -63,8 +63,16 @@ DATABASES = {
 - `DateTimeField` doesn't support microsecond precision.
 
 - The following database functions aren't supported:
+    - `Chr`
     - `ExtractQuarter`
+    - `MD5`
     - `Now`
+    - `Ord`
+    - `Pad`
+    - `Repeat`
+    - `Reverse`
+    - `Right`
+    - `SHA1`, `SHA224`, `SHA256`, `SHA384`, `SHA512`
     - `Sign`
     - `TruncDate`
     - `TruncTime`

django_mongodb/features.py

@@ -30,8 +30,10 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # Slicing with QuerySet.count() doesn't work.
         "lookup.tests.LookupTests.test_count",
         # Lookup in order_by() not supported:
-        # unsupported operand type(s) for %: 'function' and 'str'
+        # argument of type '<database function>' is not iterable
         "db_functions.comparison.test_coalesce.CoalesceTests.test_ordering",
+        "db_functions.text.test_length.LengthTests.test_ordering",
+        "db_functions.text.test_strindex.StrIndexTests.test_order_by",
         "lookup.tests.LookupQueryingTests.test_lookup_in_order_by",
         # annotate() after values() doesn't raise NotSupportedError.
         "lookup.tests.LookupTests.test_exact_query_rhs_with_selected_columns",
@@ -80,6 +82,11 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             "annotations.tests.NonAggregateAnnotationTestCase.test_update_with_annotation",
             "db_functions.comparison.test_least.LeastTests.test_update",
             "db_functions.comparison.test_greatest.GreatestTests.test_update",
+            "db_functions.text.test_left.LeftTests.test_basic",
+            "db_functions.text.test_lower.LowerTests.test_basic",
+            "db_functions.text.test_replace.ReplaceTests.test_update",
+            "db_functions.text.test_substr.SubstrTests.test_basic",
+            "db_functions.text.test_upper.UpperTests.test_basic",
             "model_fields.test_integerfield.PositiveIntegerFieldTests.test_negative_values",
             "timezones.tests.NewDatabaseTests.test_update_with_timedelta",
             "update.tests.AdvancedTests.test_update_annotated_queryset",
@@ -182,8 +189,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             "annotations.tests.NonAggregateAnnotationTestCase.test_mixed_type_annotation_numbers",
             "annotations.tests.NonAggregateAnnotationTestCase.test_q_expression_annotation_with_aggregation",
             "lookup.tests.LookupQueryingTests.test_filter_wrapped_lookup_lhs",
-            # Length not implemented.
-            "annotations.tests.NonAggregateAnnotationTestCase.test_chaining_transforms",
             # CombinedExpression not implemented.
             "annotations.tests.NonAggregateAnnotationTestCase.test_combined_annotation_commutative",
             "annotations.tests.NonAggregateAnnotationTestCase.test_decimal_annotation",
@@ -317,10 +322,25 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             "db_functions.math.test_sin.SinTests.test_transform",
             "db_functions.math.test_sqrt.SqrtTests.test_transform",
             "db_functions.math.test_tan.TanTests.test_transform",
+            "db_functions.text.test_strindex.StrIndexTests.test_filtering",
+            "db_functions.text.test_length.LengthTests.test_basic",
+            "db_functions.text.test_length.LengthTests.test_transform",
         },
         "MongoDB does not support this database function.": {
             "db_functions.datetime.test_now.NowTests",
             "db_functions.math.test_sign.SignTests",
+            "db_functions.text.test_chr.ChrTests",
+            "db_functions.text.test_md5.MD5Tests",
+            "db_functions.text.test_ord.OrdTests",
+            "db_functions.text.test_pad.PadTests",
+            "db_functions.text.test_repeat.RepeatTests",
+            "db_functions.text.test_reverse.ReverseTests",
+            "db_functions.text.test_right.RightTests",
+            "db_functions.text.test_sha1.SHA1Tests",
+            "db_functions.text.test_sha224.SHA224Tests",
+            "db_functions.text.test_sha256.SHA256Tests",
+            "db_functions.text.test_sha384.SHA384Tests",
+            "db_functions.text.test_sha512.SHA512Tests",
         },
         "ExtractQuarter database function not supported.": {
             "db_functions.datetime.test_extract_trunc.DateFunctionTests.test_extract_quarter_func",

django_mongodb/functions.py

@@ -16,7 +16,20 @@
     TruncBase,
 )
 from django.db.models.functions.math import Ceil, Cot, Degrees, Log, Power, Radians, Random, Round
-from django.db.models.functions.text import Upper
+from django.db.models.functions.text import (
+    Concat,
+    ConcatPair,
+    Left,
+    Length,
+    Lower,
+    LTrim,
+    Replace,
+    RTrim,
+    StrIndex,
+    Substr,
+    Trim,
+    Upper,
+)
 
 from .query_utils import process_lhs
 
@@ -26,6 +39,7 @@
     Degrees: "radiansToDegrees",
     Greatest: "max",
     Least: "min",
+    Lower: "toLower",
     Power: "pow",
     Radians: "degreesToRadians",
     Random: "rand",
@@ -56,6 +70,16 @@ def cast(self, compiler, connection):
     return lhs_mql
 
 
+def concat(self, compiler, connection):
+    return self.get_source_expressions()[0].as_mql(compiler, connection)
+
+
+def concat_pair(self, compiler, connection):
+    # null on either side results in null for expression, wrap with coalesce.
+    coalesced = self.coalesce()
+    return super(ConcatPair, coalesced).as_mql(compiler, connection)
+
+
 def cot(self, compiler, connection):
     lhs_mql = process_lhs(self, compiler, connection)
     return {"$divide": [1, {"$tan": lhs_mql}]}
@@ -77,6 +101,16 @@ def func(self, compiler, connection):
     return {f"${operator}": lhs_mql}
 
 
+def left(self, compiler, connection):
+    return self.get_substr().as_mql(compiler, connection)
+
+
+def length(self, compiler, connection):
+    # Check for null first since $strLenCP only accepts strings.
+    lhs_mql = process_lhs(self, compiler, connection)
+    return {"$cond": {"if": {"$eq": [lhs_mql, None]}, "then": None, "else": {"$strLenCP": lhs_mql}}}
+
+
 def log(self, compiler, connection):
     # This function is usually log(base, num) but on MongoDB it's log(num, base).
     clone = self.copy()
@@ -90,12 +124,42 @@ def null_if(self, compiler, connection):
     return {"$cond": {"if": {"$eq": [expr1, expr2]}, "then": None, "else": expr1}}
 
 
+def replace(self, compiler, connection):
+    expression, text, replacement = process_lhs(self, compiler, connection)
+    return {"$replaceAll": {"input": expression, "find": text, "replacement": replacement}}
+
+
 def round_(self, compiler, connection):
     # Round needs its own function because it's a special case that inherits
     # from Transform but has two arguments.
     return {"$round": [expr.as_mql(compiler, connection) for expr in self.get_source_expressions()]}
 
 
+def str_index(self, compiler, connection):
+    lhs = process_lhs(self, compiler, connection)
+    # StrIndex should be 0-indexed (not found) but it's -1-indexed on MongoDB.
+    return {"$add": [{"$indexOfCP": lhs}, 1]}
+
+
+def substr(self, compiler, connection):
+    lhs = process_lhs(self, compiler, connection)
+    # The starting index is zero-indexed on MongoDB rather than one-indexed.
+    lhs[1] = {"$add": [lhs[1], -1]}
+    # If no limit is specified, use the length of the string since $substrCP
+    # requires one.
+    if len(lhs) == 2:
+        lhs.append({"$strLenCP": lhs[0]})
+    return {"$substrCP": lhs}
+
+
+def trim(operator):
+    def wrapped(self, compiler, connection):
+        lhs = process_lhs(self, compiler, connection)
+        return {f"${operator}": {"input": lhs}}
+
+    return wrapped
+
+
 def trunc(self, compiler, connection):
     lhs_mql = process_lhs(self, compiler, connection)
     lhs_mql = {"date": lhs_mql, "unit": self.kind, "startOfWeek": "mon"}
@@ -106,10 +170,20 @@ def trunc(self, compiler, connection):
 
 def register_functions():
     Cast.as_mql = cast
+    Concat.as_mql = concat
+    ConcatPair.as_mql = concat_pair
     Cot.as_mql = cot
     Extract.as_mql = extract
     Func.as_mql = func
+    Left.as_mql = left
+    Length.as_mql = length
     Log.as_mql = log
+    LTrim.as_mql = trim("ltrim")
     NullIf.as_mql = null_if
+    Replace.as_mql = replace
     Round.as_mql = round_
+    RTrim.as_mql = trim("rtrim")
+    StrIndex.as_mql = str_index
+    Substr.as_mql = substr
+    Trim.as_mql = trim("trim")
     TruncBase.as_mql = trunc