From: Iuri de Silvio <iurisilvio@gmail.com>
Date: Wed, 27 Apr 2016 15:27:00 +0000 (-0500)
Subject: Support `postgresql_concurrently` on index dropping.
X-Git-Tag: rel_1_1_0b1~11
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=31a0da32a8af2503c6b94123a0e869816d83c707;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

Support `postgresql_concurrently` on index dropping.

Also adds version detection so that DROP INDEX CONCURRENTLY
only renders if the Postgresql version is 9.2 or higher;
for CREATE INDEX CONCURRENTLY, version detection is added
to allow the phrase to omit if the Postgresql version is
less than 8.2.

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: I597287e0ebbbe256c957a3579b58ace6848ab4f4
Pull-request: https://bitbucket.org/zzzeek/sqlalchemy/pull-requests/84
---

diff --git a/doc/build/changelog/changelog_11.rst b/doc/build/changelog/changelog_11.rst
index fe56c4cf33..8d20ef257d 100644
--- a/doc/build/changelog/changelog_11.rst
+++ b/doc/build/changelog/changelog_11.rst
@@ -21,6 +21,17 @@
 .. changelog::
     :version: 1.1.0b1
 
+    .. change::
+        :tags: feature, postgresql
+        :pullreq: bitbucket:84
+
+        The DDL for DROP INDEX will emit "CONCURRENTLY" if the
+        ``postgresql_concurrently`` flag is set upon the
+        :class:`.Index` and if the database in use is detected as
+        Postgresql version 9.2 or greater.   For CREATE INDEX, database
+        version detection is also added which will omit the clause if
+        PG version is less than 8.2.  Pull request courtesy Iuri de Silvio.
+
     .. change::
         :tags: bug, orm
         :tickets: 3708
diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index ec20c4b7aa..16b22129a2 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -436,11 +436,21 @@ flag ``postgresql_concurrently`` to the :class:`.Index` construct::
 
     idx1 = Index('test_idx1', tbl.c.data, postgresql_concurrently=True)
 
-The above index construct will render SQL as::
+The above index construct will render DDL for CREATE INDEX, assuming
+Postgresql 8.2 or higher is detected or for a connection-less dialect, as::
 
     CREATE INDEX CONCURRENTLY test_idx1 ON testtbl (data)
 
-.. versionadded:: 0.9.9
+For DROP INDEX, assuming Postgresql 9.2 or higher is detected or for
+a connection-less dialect, it will emit::
+
+    DROP INDEX CONCURRENTLY test_idx1
+
+.. versionadded:: 1.1 support for CONCURRENTLY on DROP INDEX.  The
+   CONCURRENTLY keyword is now only emitted if a high enough version
+   of Postgresql is detected on the connection (or for a connection-less
+   dialect).
+
 
 .. _postgresql_index_reflection:
 
@@ -1274,9 +1284,10 @@ class PGDDLCompiler(compiler.DDLCompiler):
             text += "UNIQUE "
         text += "INDEX "
 
-        concurrently = index.dialect_options['postgresql']['concurrently']
-        if concurrently:
-            text += "CONCURRENTLY "
+        if self.dialect._supports_create_index_concurrently:
+            concurrently = index.dialect_options['postgresql']['concurrently']
+            if concurrently:
+                text += "CONCURRENTLY "
 
         text += "%s ON %s " % (
             self._prepared_index_name(index,
@@ -1327,6 +1338,19 @@ class PGDDLCompiler(compiler.DDLCompiler):
             text += " WHERE " + where_compiled
         return text
 
+    def visit_drop_index(self, drop):
+        index = drop.element
+
+        text = "\nDROP INDEX "
+
+        if self.dialect._supports_drop_index_concurrently:
+            concurrently = index.dialect_options['postgresql']['concurrently']
+            if concurrently:
+                text += "CONCURRENTLY "
+
+        text += self._prepared_index_name(index, include_schema=True)
+        return text
+
     def visit_exclude_constraint(self, constraint, **kw):
         text = ""
         if constraint.name is not None:
@@ -1688,6 +1712,8 @@ class PGDialect(default.DefaultDialect):
     reflection_options = ('postgresql_ignore_search_path', )
 
     _backslash_escapes = True
+    _supports_create_index_concurrently = True
+    _supports_drop_index_concurrently = True
 
     def __init__(self, isolation_level=None, json_serializer=None,
                  json_deserializer=None, **kwargs):
@@ -1716,6 +1742,11 @@ class PGDialect(default.DefaultDialect):
             "show standard_conforming_strings"
         ) == 'off'
 
+        self._supports_create_index_concurrently = \
+            self.server_version_info >= (8, 2)
+        self._supports_drop_index_concurrently = \
+            self.server_version_info >= (9, 2)
+
     def on_connect(self):
         if self.isolation_level is not None:
             def connect(conn):
diff --git a/test/dialect/postgresql/test_compiler.py b/test/dialect/postgresql/test_compiler.py
index c8dc9582af..f85ff2682c 100644
--- a/test/dialect/postgresql/test_compiler.py
+++ b/test/dialect/postgresql/test_compiler.py
@@ -485,6 +485,32 @@ class CompileTest(fixtures.TestBase, AssertsCompiledSQL):
             "CREATE INDEX CONCURRENTLY test_idx1 ON testtbl (data)"
         )
 
+        dialect_8_1 = postgresql.dialect()
+        dialect_8_1._supports_create_index_concurrently = False
+        self.assert_compile(
+            schema.CreateIndex(idx1),
+            "CREATE INDEX test_idx1 ON testtbl (data)",
+            dialect=dialect_8_1
+        )
+
+    def test_drop_index_concurrently(self):
+        m = MetaData()
+        tbl = Table('testtbl', m, Column('data', Integer))
+
+        idx1 = Index('test_idx1', tbl.c.data, postgresql_concurrently=True)
+        self.assert_compile(
+            schema.DropIndex(idx1),
+            "DROP INDEX CONCURRENTLY test_idx1"
+        )
+
+        dialect_9_1 = postgresql.dialect()
+        dialect_9_1._supports_drop_index_concurrently = False
+        self.assert_compile(
+            schema.DropIndex(idx1),
+            "DROP INDEX test_idx1",
+            dialect=dialect_9_1
+        )
+
     def test_exclude_constraint_min(self):
         m = MetaData()
         tbl = Table('testtbl', m,