cf-5928 (draft)

.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

.clangd

@@ -0,0 +1,5 @@
+CompileFlags:
+  CompilationDatabase: build/       # Search build/ directory for compile_commands.json
+  Remove: [ -Werror ]
+  Add: [ -DPGDLLIMPORT= ]
+

.envrc

@@ -0,0 +1,2 @@
+watch_file flake.nix
+use flake

.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 +1,6 @@
+{
+    "files.associations": {
+        "syscache.h": "c",
+        "random": "c"
+    }
+}

contrib/pg_prewarm/autoprewarm.c

@@ -370,6 +370,16 @@ apw_load_buffers(void)
 	apw_state->prewarm_start_idx = apw_state->prewarm_stop_idx = 0;
 	apw_state->prewarmed_blocks = 0;
 
+
+	/* Don't prewarm more than we can fit. */
+	if (num_elements > NBuffers)
+	{
+		num_elements = NBuffers;
+		ereport(LOG,
+				(errmsg("autoprewarm: capping prewarmed blocks to %d (shared_buffers size)",
+						NBuffers)));
+	}
+
 	/* Get the info position of the first block of the next database. */
 	while (apw_state->prewarm_start_idx < num_elements)
 	{
@@ -410,10 +420,6 @@ apw_load_buffers(void)
 		apw_state->database = current_db;
 		Assert(apw_state->prewarm_start_idx < apw_state->prewarm_stop_idx);
 
-		/* If we've run out of free buffers, don't launch another worker. */
-		if (!have_free_buffer())
-			break;
-
 		/*
 		 * Likewise, don't launch if we've already been told to shut down.
 		 * (The launch would fail anyway, but we might as well skip it.)
@@ -462,12 +468,6 @@ apw_read_stream_next_block(ReadStream *stream,
 	{
 		BlockInfoRecord blk = p->block_info[p->pos];
 
-		if (!have_free_buffer())
-		{
-			p->pos = apw_state->prewarm_stop_idx;
-			return InvalidBlockNumber;
-		}
-
 		if (blk.tablespace != p->tablespace)
 			return InvalidBlockNumber;
 
@@ -523,10 +523,10 @@ autoprewarm_database_main(Datum main_arg)
 	blk = block_info[i];
 
 	/*
-	 * Loop until we run out of blocks to prewarm or until we run out of free
+	 * Loop until we run out of blocks to prewarm or until we run out of
 	 * buffers.
 	 */
-	while (i < apw_state->prewarm_stop_idx && have_free_buffer())
+	while (i < apw_state->prewarm_stop_idx)
 	{
 		Oid			tablespace = blk.tablespace;
 		RelFileNumber filenumber = blk.filenumber;
@@ -568,14 +568,13 @@ autoprewarm_database_main(Datum main_arg)
 
 		/*
 		 * We have a relation; now let's loop until we find a valid fork of
-		 * the relation or we run out of free buffers. Once we've read from
-		 * all valid forks or run out of options, we'll close the relation and
+		 * the relation or we run out of buffers. Once we've read from all
+		 * valid forks or run out of options, we'll close the relation and
 		 * move on.
 		 */
 		while (i < apw_state->prewarm_stop_idx &&
 			   blk.tablespace == tablespace &&
-			   blk.filenumber == filenumber &&
-			   have_free_buffer())
+			   blk.filenumber == filenumber)
 		{
 			ForkNumber	forknum = blk.forknum;
 			BlockNumber nblocks;

flake.nix

@@ -0,0 +1,39 @@
+{
+  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 {
+        formatter = pkgs.alejandra;
+        devShells = {
+          default = shellConfig.devShell;
+          gcc = shellConfig.devShell;
+          clang = shellConfig.clangDevShell;
+          gcc-musl = shellConfig.muslDevShell;
+          clang-musl = shellConfig.clangMuslDevShell;
+        };
+
+        packages = {
+          inherit (shellConfig) gdbConfig flameGraphScript pgbenchScript;
+        };
+
+        environment.localBinInPath = true;
+      }
+    );
+}