From: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Date: Sat, 8 Jan 2022 23:01:56 +0000 (+0100)
Subject: feat: add Transformer.from_context() method
X-Git-Tag: 3.1~109^2~12
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=26ccbdb1d0db41ebd4037b8b8ecfb36cc351a8e6;p=thirdparty%2Fpsycopg.git

feat: add Transformer.from_context() method

Allow to reuse the same transformer in nested context, instead of
creating new ones. Even if transformer copies are shallow, we may end up
creating several in certain places.
---

diff --git a/psycopg/psycopg/_transform.py b/psycopg/psycopg/_transform.py
index 11194558b..4f93f3639 100644
--- a/psycopg/psycopg/_transform.py
+++ b/psycopg/psycopg/_transform.py
@@ -75,6 +75,18 @@ class Transformer(AdaptContext):
         # the length of the result columns
         self._row_loaders: List[LoadFunc] = []
 
+    @classmethod
+    def from_context(cls, context: Optional[AdaptContext]) -> "Transformer":
+        """
+        Return a Transformer from an AdaptContext.
+
+        If the context is a Transformer instance, just return it.
+        """
+        if isinstance(context, Transformer):
+            return context
+        else:
+            return cls(context)
+
     @property
     def connection(self) -> Optional["BaseConnection[Any]"]:
         return self._conn
diff --git a/psycopg/psycopg/abc.py b/psycopg/psycopg/abc.py
index d23873fe5..0bbcebe29 100644
--- a/psycopg/psycopg/abc.py
+++ b/psycopg/psycopg/abc.py
@@ -196,6 +196,10 @@ class Transformer(Protocol):
     def __init__(self, context: Optional[AdaptContext] = None):
         ...
 
+    @classmethod
+    def from_context(cls, context: Optional[AdaptContext]) -> "Transformer":
+        ...
+
     @property
     def connection(self) -> Optional["BaseConnection[Any]"]:
         ...
diff --git a/psycopg/psycopg/adapt.py b/psycopg/psycopg/adapt.py
index 8341a5a29..ccf89ce2f 100644
--- a/psycopg/psycopg/adapt.py
+++ b/psycopg/psycopg/adapt.py
@@ -151,7 +151,7 @@ class RecursiveDumper(Dumper):
 
     def __init__(self, cls: type, context: Optional[abc.AdaptContext] = None):
         super().__init__(cls, context)
-        self._tx = Transformer(context)
+        self._tx = Transformer.from_context(context)
 
 
 class RecursiveLoader(Loader):
@@ -159,4 +159,4 @@ class RecursiveLoader(Loader):
 
     def __init__(self, oid: int, context: Optional[abc.AdaptContext] = None):
         super().__init__(oid, context)
-        self._tx = Transformer(context)
+        self._tx = Transformer.from_context(context)
diff --git a/psycopg/psycopg/sql.py b/psycopg/psycopg/sql.py
index ade3e4de4..39ecfc9e8 100644
--- a/psycopg/psycopg/sql.py
+++ b/psycopg/psycopg/sql.py
@@ -390,7 +390,7 @@ class Literal(Composable):
     """
 
     def as_bytes(self, context: Optional[AdaptContext]) -> bytes:
-        tx = Transformer(context)
+        tx = Transformer.from_context(context)
         dumper = tx.get_dumper(self._obj, PyFormat.TEXT)
         return dumper.quote(self._obj)
 
diff --git a/psycopg/psycopg/types/composite.py b/psycopg/psycopg/types/composite.py
index a5340993e..4174854b1 100644
--- a/psycopg/psycopg/types/composite.py
+++ b/psycopg/psycopg/types/composite.py
@@ -13,7 +13,7 @@ from typing import Sequence, Tuple, Type
 from .. import pq
 from .. import postgres
 from ..abc import AdaptContext, Buffer
-from ..adapt import PyFormat, RecursiveDumper, RecursiveLoader
+from ..adapt import Transformer, PyFormat, RecursiveDumper, Loader
 from .._struct import pack_len, unpack_len
 from ..postgres import TEXT_OID
 from .._typeinfo import CompositeInfo as CompositeInfo  # exported here
@@ -94,7 +94,11 @@ class TupleBinaryDumper(RecursiveDumper):
         return out
 
 
-class BaseCompositeLoader(RecursiveLoader):
+class BaseCompositeLoader(Loader):
+    def __init__(self, oid: int, context: Optional[AdaptContext] = None):
+        super().__init__(oid, context)
+        self._tx = Transformer(context)
+
     def _parse_record(self, data: bytes) -> Iterator[Optional[bytes]]:
         """
         Split a non-empty representation of a composite type into components.
@@ -138,11 +142,14 @@ class RecordLoader(BaseCompositeLoader):
         )
 
 
-class RecordBinaryLoader(RecursiveLoader):
-
+class RecordBinaryLoader(Loader):
     format = pq.Format.BINARY
     _types_set = False
 
+    def __init__(self, oid: int, context: Optional[AdaptContext] = None):
+        super().__init__(oid, context)
+        self._tx = Transformer(context)
+
     def load(self, data: Buffer) -> Tuple[Any, ...]:
         if not self._types_set:
             self._config_types(data)
diff --git a/psycopg_c/psycopg_c/_psycopg.pyi b/psycopg_c/psycopg_c/_psycopg.pyi
index 6668e337f..3bcd4961d 100644
--- a/psycopg_c/psycopg_c/_psycopg.pyi
+++ b/psycopg_c/psycopg_c/_psycopg.pyi
@@ -22,6 +22,8 @@ class Transformer(abc.AdaptContext):
     types: Optional[Tuple[int, ...]]
     formats: Optional[List[pq.Format]]
     def __init__(self, context: Optional[abc.AdaptContext] = None): ...
+    @classmethod
+    def from_context(cls, context: Optional[abc.AdaptContext]) -> "Transformer": ...
     @property
     def connection(self) -> Optional[BaseConnection[Any]]: ...
     @property
diff --git a/psycopg_c/psycopg_c/_psycopg/transform.pyx b/psycopg_c/psycopg_c/_psycopg/transform.pyx
index ffd8bf99e..9544de84f 100644
--- a/psycopg_c/psycopg_c/_psycopg/transform.pyx
+++ b/psycopg_c/psycopg_c/_psycopg/transform.pyx
@@ -104,6 +104,18 @@ cdef class Transformer:
 
         self.types = self.formats = None
 
+    @classmethod
+    def from_context(cls, context: Optional["AdaptContext"]):
+        """
+        Return a Transformer from an AdaptContext.
+
+        If the context is a Transformer instance, just return it.
+        """
+        if isinstance(context, Transformer):
+            return context
+        else:
+            return cls(context)
+
     @property
     def pgresult(self) -> Optional[PGresult]:
         return self._pgresult