heap: partial-HOT index update improvements (phot)

.clang-format

@@ -0,0 +1,71 @@
+# the official .clang-format style for https://github.com/taocpp
+#
+# clang-format-4.0 -i -style=file $(find -name '[^.]*.[hc]pp')
+
+Language: Cpp
+Standard: Cpp11
+
+AccessModifierOffset: -3
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlinesLeft: false
+AlignOperands: true
+AlignTrailingComments: true
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: true
+BinPackArguments: false
+BinPackParameters: false
+BraceWrapping:
+    AfterClass: true
+    AfterControlStatement: false
+    AfterEnum : true
+    AfterFunction : true
+    AfterNamespace : true
+    AfterStruct : true
+    AfterUnion : true
+    BeforeCatch : true
+    BeforeElse : true
+    IndentBraces : false
+BreakBeforeBinaryOperators: All
+BreakBeforeBraces: Custom
+BreakBeforeTernaryOperators: false
+BreakStringLiterals: false
+BreakConstructorInitializersBeforeComma: false
+ColumnLimit: 0
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+ConstructorInitializerIndentWidth: 3
+ContinuationIndentWidth: 3
+Cpp11BracedListStyle: false
+DerivePointerAlignment: false
+DisableFormat: false
+ExperimentalAutoDetectBinPacking: false
+IndentCaseLabels: true
+IndentWidth: 3
+IndentWrappedFunctionNames: false
+KeepEmptyLinesAtTheStartOfBlocks: true
+MaxEmptyLinesToKeep: 1
+NamespaceIndentation: All
+PointerAlignment: Left
+ReflowComments: false
+SortIncludes: true
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: false
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: Never
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 2
+SpacesInAngles: true
+SpacesInCStyleCastParentheses: false
+SpacesInContainerLiterals: true
+SpacesInParentheses: true
+SpacesInSquareBrackets: true
+TabWidth: 8
+UseTab: Never

.envrc

@@ -0,0 +1,18 @@
+# Bootstrap nix-direnv (ensures specific version, robust)
+if ! has nix_direnv_version || ! nix_direnv_version 3.0.4; then
+        source_url "https://raw.githubusercontent.com/nix-community/nix-direnv/3.0.4/direnvrc" "sha256-DzlYZ33mWF/Gs8DDeyjr8mnVmQGx7ASYqA5WlxwvBG4="
+fi
+
+# Watch flake.nix for changes to reload the environment
+watch_file flake.nix
+
+# Use the Nix flake to provide the development environment
+use flake
+
+# Set consistent locale for development environment
+#export LANGUAGE=C.utf8
+#export LANG=C.utf8
+#export LC_ALL=C.utf8
+
+# IKOS-specific environment variable (keep if needed for your IKOS workflow)
+export IKOS_SCAN_NOTIFIER_FILES=""

.gitignore

@@ -43,3 +43,11 @@ lib*.pc
 /Release/
 /tmp_install/
 /portlock/
+
+build/
+install/
+test-db/
+.direnv/
+.cache/
+.history
+

.vscode/launch.json

@@ -0,0 +1,22 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "(gdb) Attach Postgres",
+            "type": "cppdbg",
+            "request": "attach",
+            "program": "${workspaceRoot}/install/bin/postgres",
+            "MIMode": "gdb",
+            "setupCommands": [
+                {
+                    "description": "Enable pretty-printing for gdb",
+                    "text": "-enable-pretty-printing",
+                    "ignoreFailures": true
+                }
+            ],
+        }
+    ]
+}

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "files.associations": {
+        "syscache.h": "c"
+    }
+}

doc/src/sgml/ref/create_table.sgml

@@ -1997,6 +1997,24 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
     </listitem>
    </varlistentry>
 
+   <varlistentry id="reloption-expression-checks" xreflabel="expression_checks">
+    <term><literal>expression_checks</literal> (<type>boolean</type>)
+    <indexterm>
+     <primary><varname>expression_checks</varname> storage parameter</primary>
+    </indexterm>
+    </term>
+    <listitem>
+     <para>
+      Enables or disables evaulation of predicate expressions on partial
+      indexes or expressions used to define indexes during updates.
+      If <literal>true</literal>, then these expressions are evaluated during
+      updates to data within the heap relation against the old and new values
+      and then compared to determine if <acronym>HOT</acronym> updates are
+      allowable or not. The default value is <literal>true</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
    </variablelist>
 
   </refsect2>

doc/src/sgml/storage.sgml

@@ -1097,10 +1097,10 @@ data. Empty in ordinary tables.</entry>
   <itemizedlist>
    <listitem>
     <para>
-     The update does not modify any columns referenced by the table's indexes,
-     not including summarizing indexes.  The only summarizing index method in
-     the core <productname>PostgreSQL</productname> distribution is <link
-     linkend="brin">BRIN</link>.
+     The update does not modify index keys, or when using a summarized
+     index.  The only summarizing index method in the core
+     <productname>PostgreSQL</productname> distribution is
+     <link linkend="brin">BRIN</link>.
      </para>
    </listitem>
    <listitem>
@@ -1138,6 +1138,27 @@ data. Empty in ordinary tables.</entry>
   </itemizedlist>
  </para>
 
+ <para>
+  <acronym>HOT</acronym> updates can occur when the expression used to define
+  an index shows no changes to the indexed value. To determine this requires
+  that the expression be evaulated for the old and new values to be stored in
+  the index and then compared. This allows for <acronym>HOT</acronym> updates
+  when data indexed within JSONB columns is unchanged. To disable this
+  behavior and avoid the overhead of evaluating the expression during updates
+  set the <literal>expression_checks</literal> option to false for the table.
+ </para>
+
+ <para>
+  <acronym>HOT</acronym> updates can also occur when updated values are not
+  within the predicate of a partial index. However, <acronym>HOT</acronym>
+  updates are not possible when the updated value and the current value differ
+  with regards to the predicate. To determine this requires that the predicate
+  expression be evaluated for the old and new values to be stored in the index
+  and then compared. To disable this behavior and avoid the overhead of
+  evaluating the expression during updates set
+  the <literal>expression_checks</literal> option to false for the table.
+ </para>
+
  <para>
   You can increase the likelihood of sufficient page space for
   <acronym>HOT</acronym> updates by decreasing a table's <link

flake.nix

@@ -0,0 +1,33 @@
+{
+  description = "PostgreSQL development environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          config.allowUnfree = true;
+        };
+
+        shellConfig = import ./shell.nix { inherit pkgs system; };
+
+      in {
+        devShells = {
+          default = shellConfig.devShell;
+          gcc = shellConfig.devShell;
+          clang = shellConfig.clangDevShell;
+          gcc-musl = shellConfig.muslDevShell;
+          clang-musl = shellConfig.clangMuslDevShell;
+        };
+
+        packages = {
+          inherit (shellConfig) gdbConfig flameGraphScript pgbenchScript;
+        };
+      }
+    );
+}