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[PATCH 3/5] pg_rewind: Replace the hybrid list+array data structure with simplehash.
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* [PATCH 3/5] pg_rewind: Replace the hybrid list+array data structure with simplehash.
@ 2020-08-19 12:34  Heikki Linnakangas <[email protected]>
  0 siblings, 0 replies; 3+ messages in thread

From: Heikki Linnakangas @ 2020-08-19 12:34 UTC (permalink / raw)

Now that simplehash can be use in frontend code, let's make use of it.
---
 src/bin/pg_rewind/copy_fetch.c  |   4 +-
 src/bin/pg_rewind/fetch.c       |   2 +-
 src/bin/pg_rewind/fetch.h       |   2 +-
 src/bin/pg_rewind/filemap.c     | 284 ++++++++++++++------------------
 src/bin/pg_rewind/filemap.h     |  67 +++-----
 src/bin/pg_rewind/libpq_fetch.c |   4 +-
 src/bin/pg_rewind/pg_rewind.c   |  12 +-
 7 files changed, 168 insertions(+), 207 deletions(-)

diff --git a/src/bin/pg_rewind/copy_fetch.c b/src/bin/pg_rewind/copy_fetch.c
index 18fad32600e..61aed8018b6 100644
--- a/src/bin/pg_rewind/copy_fetch.c
+++ b/src/bin/pg_rewind/copy_fetch.c
@@ -207,9 +207,9 @@ copy_executeFileMap(filemap_t *map)
 	file_entry_t *entry;
 	int			i;
 
-	for (i = 0; i < map->narray; i++)
+	for (i = 0; i < map->nactions; i++)
 	{
-		entry = map->array[i];
+		entry = map->actions[i];
 		execute_pagemap(&entry->target_modified_pages, entry->path);
 
 		switch (entry->action)
diff --git a/src/bin/pg_rewind/fetch.c b/src/bin/pg_rewind/fetch.c
index f18fe5386ed..f41d0f295ea 100644
--- a/src/bin/pg_rewind/fetch.c
+++ b/src/bin/pg_rewind/fetch.c
@@ -37,7 +37,7 @@ fetchSourceFileList(void)
  * Fetch all relation data files that are marked in the given data page map.
  */
 void
-executeFileMap(void)
+execute_file_actions(filemap_t *filemap)
 {
 	if (datadir_source)
 		copy_executeFileMap(filemap);
diff --git a/src/bin/pg_rewind/fetch.h b/src/bin/pg_rewind/fetch.h
index 7cf8b6ea090..b20df8b1537 100644
--- a/src/bin/pg_rewind/fetch.h
+++ b/src/bin/pg_rewind/fetch.h
@@ -25,7 +25,7 @@
  */
 extern void fetchSourceFileList(void);
 extern char *fetchFile(const char *filename, size_t *filesize);
-extern void executeFileMap(void);
+extern void execute_file_actions(filemap_t *filemap);
 
 /* in libpq_fetch.c */
 extern void libpqProcessFileList(void);
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 431e8e760e0..6d48b6076e3 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -3,6 +3,19 @@
  * filemap.c
  *	  A data structure for keeping track of files that have changed.
  *
+ * This source file contains the logic to decide what to do with different
+ * kinds of files, and the data structure to support it.  Before modifying
+ * anything, pg_rewind collects information about all the files and their
+ * attributes in the target and source data directories.  It also scans the
+ * WAL log in the target, and collects information about data blocks that
+ * were changed.  All this information is stored in a hash table, using the
+ * file path, relative to the root of the data directory, as the key.
+ *
+ * After collecting all the information required, the filemap_finalize()
+ * function scans the hash table and decides what action needs to be taken
+ * for each file.  Finally, it sorts the array to the final order that the
+ * actions should be executed in.
+ *
  * Copyright (c) 2013-2020, PostgreSQL Global Development Group
  *
  *-------------------------------------------------------------------------
@@ -14,22 +27,39 @@
 #include <unistd.h>
 
 #include "catalog/pg_tablespace_d.h"
+#include "common/hashfn.h"
 #include "common/string.h"
 #include "datapagemap.h"
 #include "filemap.h"
 #include "pg_rewind.h"
 #include "storage/fd.h"
 
-filemap_t  *filemap = NULL;
+/*
+ * Define a hash table which we can use to store information about the files
+ * mentioned in the backup manifest.
+ */
+static uint32 hash_string_pointer(const char *s);
+#define SH_PREFIX		filehash
+#define SH_ELEMENT_TYPE	file_entry_t
+#define SH_KEY_TYPE		const char *
+#define	SH_KEY			path
+#define SH_HASH_KEY(tb, key)	hash_string_pointer(key)
+#define SH_EQUAL(tb, a, b)		(strcmp(a, b) == 0)
+#define	SH_SCOPE		static inline
+#define SH_RAW_ALLOCATOR	pg_malloc0
+#define SH_DECLARE
+#define SH_DEFINE
+#include "lib/simplehash.h"
+
+static filehash_hash *filehash;
 
 static bool isRelDataFile(const char *path);
 static char *datasegpath(RelFileNode rnode, ForkNumber forknum,
 						 BlockNumber segno);
-static int	path_cmp(const void *a, const void *b);
 
-static file_entry_t *get_filemap_entry(const char *path, bool create);
+static file_entry_t *insert_filehash_entry(const char *path);
+static file_entry_t *lookup_filehash_entry(const char *path);
 static int	final_filemap_cmp(const void *a, const void *b);
-static void filemap_list_to_array(filemap_t *map);
 static bool check_file_excluded(const char *path, bool is_source);
 
 /*
@@ -131,54 +161,26 @@ static const struct exclude_list_item excludeFiles[] =
 };
 
 /*
- * Create a new file map (stored in the global pointer "filemap").
+ * Initialize the hash table for the file map.
  */
 void
-filemap_create(void)
+filemap_init(void)
 {
-	filemap_t  *map;
-
-	map = pg_malloc(sizeof(filemap_t));
-	map->first = map->last = NULL;
-	map->nlist = 0;
-	map->array = NULL;
-	map->narray = 0;
-
-	Assert(filemap == NULL);
-	filemap = map;
+	filehash = filehash_create(1000, NULL);
 }
 
-/* Look up or create entry for 'path' */
+/* Look up entry for 'path', creating new one if it doesn't exists */
 static file_entry_t *
-get_filemap_entry(const char *path, bool create)
+insert_filehash_entry(const char *path)
 {
-	filemap_t  *map = filemap;
 	file_entry_t *entry;
-	file_entry_t **e;
-	file_entry_t key;
-	file_entry_t *key_ptr;
+	bool		found;
 
-	if (map->array)
+	entry = filehash_insert(filehash, path, &found);
+	if (!found)
 	{
-		key.path = (char *) path;
-		key_ptr = &key;
-		e = bsearch(&key_ptr, map->array, map->narray, sizeof(file_entry_t *),
-					path_cmp);
-	}
-	else
-		e = NULL;
-
-	if (e)
-		entry = *e;
-	else if (!create)
-		entry = NULL;
-	else
-	{
-		/* Create a new entry for this file */
-		entry = pg_malloc(sizeof(file_entry_t));
 		entry->path = pg_strdup(path);
 		entry->isrelfile = isRelDataFile(path);
-		entry->action = FILE_ACTION_UNDECIDED;
 
 		entry->target_exists = false;
 		entry->target_type = FILE_TYPE_UNDEFINED;
@@ -192,21 +194,18 @@ get_filemap_entry(const char *path, bool create)
 		entry->source_size = 0;
 		entry->source_link_target = NULL;
 
-		entry->next = NULL;
-
-		if (map->last)
-		{
-			map->last->next = entry;
-			map->last = entry;
-		}
-		else
-			map->first = map->last = entry;
-		map->nlist++;
+		entry->action = FILE_ACTION_UNDECIDED;
 	}
 
 	return entry;
 }
 
+static file_entry_t *
+lookup_filehash_entry(const char *path)
+{
+	return filehash_lookup(filehash, path);
+}
+
 /*
  * Callback for processing source file list.
  *
@@ -220,8 +219,6 @@ process_source_file(const char *path, file_type_t type, size_t size,
 {
 	file_entry_t *entry;
 
-	Assert(filemap->array == NULL);
-
 	/*
 	 * Skip the control file. It is handled specially, after copying all the
 	 * other files.
@@ -262,7 +259,9 @@ process_source_file(const char *path, file_type_t type, size_t size,
 		pg_fatal("data file \"%s\" in source is not a regular file", path);
 
 	/* Remember this source file */
-	entry = get_filemap_entry(path, true);
+	entry = insert_filehash_entry(path);
+	if (entry->source_exists)
+		pg_fatal("duplicate source file \"%s\"", path);
 	entry->source_exists = true;
 	entry->source_type = type;
 	entry->source_size = size;
@@ -280,7 +279,6 @@ void
 process_target_file(const char *path, file_type_t type, size_t size,
 					const char *link_target)
 {
-	filemap_t  *map = filemap;
 	file_entry_t *entry;
 
 	/*
@@ -295,21 +293,6 @@ process_target_file(const char *path, file_type_t type, size_t size,
 	 * from the target data folder all paths which have been filtered out from
 	 * the source data folder when processing the source files.
 	 */
-	if (map->array == NULL)
-	{
-		/* on first call, initialize lookup array */
-		if (map->nlist == 0)
-		{
-			/* should not happen */
-			pg_fatal("source file list is empty");
-		}
-
-		filemap_list_to_array(map);
-
-		Assert(map->array != NULL);
-
-		qsort(map->array, map->narray, sizeof(file_entry_t *), path_cmp);
-	}
 
 	/*
 	 * Like in process_source_file, pretend that pg_wal is always a directory.
@@ -318,7 +301,9 @@ process_target_file(const char *path, file_type_t type, size_t size,
 		type = FILE_TYPE_DIRECTORY;
 
 	/* Remember this target file */
-	entry = get_filemap_entry(path, true);
+	entry = insert_filehash_entry(path);
+	if (entry->target_exists)
+		pg_fatal("duplicate source file \"%s\"", path);
 	entry->target_exists = true;
 	entry->target_type = type;
 	entry->target_size = size;
@@ -331,7 +316,7 @@ process_target_file(const char *path, file_type_t type, size_t size,
  * changed blocks in the pagemap of the file.
  *
  * NOTE: All the files on both systems must have already been added to the
- * file map!
+ * hash table!
  */
 void
 process_target_wal_block_change(ForkNumber forknum, RelFileNode rnode,
@@ -342,47 +327,45 @@ process_target_wal_block_change(ForkNumber forknum, RelFileNode rnode,
 	BlockNumber blkno_inseg;
 	int			segno;
 
-	Assert(filemap->array);
-
 	segno = blkno / RELSEG_SIZE;
 	blkno_inseg = blkno % RELSEG_SIZE;
 
 	path = datasegpath(rnode, forknum, segno);
-	entry = get_filemap_entry(path, false);
+	entry = lookup_filehash_entry(path);
 	pfree(path);
 
+	/*
+	 * If the block still exists in both systems, remember it. Otherwise we
+	 * can safely ignore it.
+	 *
+	 * If the block is beyond the EOF in the source system, or the file doesn't
+	 * doesn'exist in the source at all, we're going to truncate/remove it away
+	 * from the target anyway. Likewise, if it doesn't exist in the target
+	 * anymore, we will copy it over with the "tail" from the source system,
+	 * anyway.
+	 *
+	 * It is possible to find WAL for a file that doesn't exist on either
+	 * system anymore. It means that the relation was dropped later in the
+	 * target system, and independently on the source system too, or that
+	 * it was created and dropped in the target system and it never existed
+	 * in the source. Either way, we can safely ignore it.
+	 */
 	if (entry)
 	{
-		int64		end_offset;
-
 		Assert(entry->isrelfile);
 
 		if (entry->target_type != FILE_TYPE_REGULAR)
 			pg_fatal("unexpected page modification for directory or symbolic link \"%s\"",
 					 entry->path);
 
-		/*
-		 * If the block beyond the EOF in the source system, no need to
-		 * remember it now, because we're going to truncate it away from the
-		 * target anyway. Also no need to remember the block if it's beyond
-		 * the current EOF in the target system; we will copy it over with the
-		 * "tail" from the source system, anyway.
-		 */
-		end_offset = (blkno_inseg + 1) * BLCKSZ;
-		if (end_offset <= entry->source_size &&
-			end_offset <= entry->target_size)
-			datapagemap_add(&entry->target_modified_pages, blkno_inseg);
-	}
-	else
-	{
-		/*
-		 * If we don't have any record of this file in the file map, it means
-		 * that it's a relation that doesn't exist in the source system.  It
-		 * could exist in the target system; we haven't moved the target-only
-		 * entries from the linked list to the array yet!  But in any case, if
-		 * it doesn't exist in the source it will be removed from the target
-		 * too, and we can safely ignore it.
-		 */
+		if (entry->target_exists && entry->source_exists)
+		{
+			off_t		end_offset;
+
+			end_offset = (blkno_inseg + 1) * BLCKSZ;
+			if (end_offset <= entry->source_size && end_offset <= entry->target_size)
+				datapagemap_add(&entry->target_modified_pages, blkno_inseg);
+		}
 	}
 }
 
@@ -444,34 +427,6 @@ check_file_excluded(const char *path, bool is_source)
 	return false;
 }
 
-/*
- * Convert the linked list of entries in map->first/last to the array,
- * map->array.
- */
-static void
-filemap_list_to_array(filemap_t *map)
-{
-	int			narray;
-	file_entry_t *entry,
-			   *next;
-
-	map->array = (file_entry_t **)
-		pg_realloc(map->array,
-				   (map->nlist + map->narray) * sizeof(file_entry_t *));
-
-	narray = map->narray;
-	for (entry = map->first; entry != NULL; entry = next)
-	{
-		map->array[narray++] = entry;
-		next = entry->next;
-		entry->next = NULL;
-	}
-	Assert(narray == map->nlist + map->narray);
-	map->narray = narray;
-	map->nlist = 0;
-	map->first = map->last = NULL;
-}
-
 static const char *
 action_to_str(file_action_t action)
 {
@@ -499,32 +454,31 @@ action_to_str(file_action_t action)
  * Calculate the totals needed for progress reports.
  */
 void
-calculate_totals(void)
+calculate_totals(filemap_t *filemap)
 {
 	file_entry_t *entry;
 	int			i;
-	filemap_t  *map = filemap;
 
-	map->total_size = 0;
-	map->fetch_size = 0;
+	filemap->total_size = 0;
+	filemap->fetch_size = 0;
 
-	for (i = 0; i < map->narray; i++)
+	for (i = 0; i < filemap->nactions; i++)
 	{
-		entry = map->array[i];
+		entry = filemap->actions[i];
 
 		if (entry->source_type != FILE_TYPE_REGULAR)
 			continue;
 
-		map->total_size += entry->source_size;
+		filemap->total_size += entry->source_size;
 
 		if (entry->action == FILE_ACTION_COPY)
 		{
-			map->fetch_size += entry->source_size;
+			filemap->fetch_size += entry->source_size;
 			continue;
 		}
 
 		if (entry->action == FILE_ACTION_COPY_TAIL)
-			map->fetch_size += (entry->source_size - entry->target_size);
+			filemap->fetch_size += (entry->source_size - entry->target_size);
 
 		if (entry->target_modified_pages.bitmapsize > 0)
 		{
@@ -533,7 +487,7 @@ calculate_totals(void)
 
 			iter = datapagemap_iterate(&entry->target_modified_pages);
 			while (datapagemap_next(iter, &blk))
-				map->fetch_size += BLCKSZ;
+				filemap->fetch_size += BLCKSZ;
 
 			pg_free(iter);
 		}
@@ -541,15 +495,14 @@ calculate_totals(void)
 }
 
 void
-print_filemap(void)
+print_filemap(filemap_t *filemap)
 {
-	filemap_t  *map = filemap;
 	file_entry_t *entry;
 	int			i;
 
-	for (i = 0; i < map->narray; i++)
+	for (i = 0; i < filemap->nactions; i++)
 	{
-		entry = map->array[i];
+		entry = filemap->actions[i];
 		if (entry->action != FILE_ACTION_NONE ||
 			entry->target_modified_pages.bitmapsize > 0)
 		{
@@ -671,15 +624,6 @@ datasegpath(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
 		return path;
 }
 
-static int
-path_cmp(const void *a, const void *b)
-{
-	file_entry_t *fa = *((file_entry_t **) a);
-	file_entry_t *fb = *((file_entry_t **) b);
-
-	return strcmp(fa->path, fb->path);
-}
-
 /*
  * In the final stage, the filemap is sorted so that removals come last.
  * From disk space usage point of view, it would be better to do removals
@@ -710,16 +654,17 @@ final_filemap_cmp(const void *a, const void *b)
 /*
  * Decide what to do with each file.
  */
-void
+filemap_t *
 filemap_finalize()
 {
 	int			i;
+	filehash_iterator it;
+	file_entry_t *entry;
+	filemap_t  *filemap;
 
-	filemap_list_to_array(filemap);
-
-	for (i = 0; i < filemap->narray; i++)
+	filehash_start_iterate(filehash, &it);
+	while ((entry = filehash_iterate(filehash, &it)) != NULL)
 	{
-		file_entry_t *entry = filemap->array[i];
 		file_action_t action;
 
 		if (!entry->target_exists && entry->source_exists)
@@ -825,7 +770,34 @@ filemap_finalize()
 		entry->action = action;
 	}
 
-	/* Sort the actions to the order that they should be performed */
-	qsort(filemap->array, filemap->narray, sizeof(file_entry_t *),
+	/*
+	 * Turn the hash table into an array, sorted in the order that the actions
+	 * should be performed.
+	 */
+	filemap = pg_malloc(offsetof(filemap_t, actions) +
+						filehash->members * sizeof(file_entry_t *));
+	filemap->nactions = filehash->members;
+	filehash_start_iterate(filehash, &it);
+	i = 0;
+	while ((entry = filehash_iterate(filehash, &it)) != NULL)
+	{
+		filemap->actions[i++] = entry;
+	}
+
+	qsort(&filemap->actions, filemap->nactions, sizeof(file_entry_t *),
 		  final_filemap_cmp);
+
+	return filemap;
+}
+
+
+/*
+ * Helper function for filemap hash table.
+ */
+static uint32
+hash_string_pointer(const char *s)
+{
+	unsigned char *ss = (unsigned char *) s;
+
+	return hash_bytes(ss, strlen(s));
 }
diff --git a/src/bin/pg_rewind/filemap.h b/src/bin/pg_rewind/filemap.h
index a5e8df57f40..3660ffe0990 100644
--- a/src/bin/pg_rewind/filemap.h
+++ b/src/bin/pg_rewind/filemap.h
@@ -12,15 +12,6 @@
 #include "storage/block.h"
 #include "storage/relfilenode.h"
 
-/*
- * For every file found in the local or remote system, we have a file entry
- * that contains information about the file on both systems.  For relation
- * files, there is also a page map that marks pages in the file that were
- * changed in the target after the last common checkpoint.  Each entry also
- * contains an 'action' field, which says what we are going to do with the
- * file.
- */
-
 /* these enum values are sorted in the order we want actions to be processed */
 typedef enum
 {
@@ -44,9 +35,21 @@ typedef enum
 	FILE_TYPE_SYMLINK
 } file_type_t;
 
+/*
+ * For every file found in the local or remote system, we have a file entry
+ * that contains information about the file on both systems.  For relation
+ * files, there is also a page map that marks pages in the file that were
+ * changed in the target after the last common checkpoint.
+ *
+ * When gathering information, these are kept in a hash table, private to
+ * filemap.c. filemap_finalize() fills in the 'action' field, sorts all the
+ * entries, and returns them in an array, ready for executing the actions.
+ */
 typedef struct file_entry_t
 {
-	char	   *path;
+	uint32		status;			/* hash status */
+
+	const char *path;
 	bool		isrelfile;		/* is it a relation data file? */
 
 	/*
@@ -71,44 +74,25 @@ typedef struct file_entry_t
 	 * What will we do to the file?
 	 */
 	file_action_t action;
-
-	struct file_entry_t *next;
 } file_entry_t;
 
+/*
+ * This represents the final decisions on what to do with each file.
+ * 'actions' array contains an entry for each file, sorted in the order
+ * that their actions should executed.
+ */
 typedef struct filemap_t
 {
-	/*
-	 * New entries are accumulated to a linked list, in process_source_file
-	 * and process_target_file.
-	 */
-	file_entry_t *first;
-	file_entry_t *last;
-	int			nlist;			/* number of entries currently in list */
-
-	/*
-	 * After processing all the remote files, the entries in the linked list
-	 * are moved to this array.  After processing local files, too, all the
-	 * local entries are added to the array by filemap_finalize, and sorted in
-	 * the final order.  After filemap_finalize, all the entries are in the
-	 * array, and the linked list is empty.
-	 */
-	file_entry_t **array;
-	int			narray;			/* current length of array */
-
-	/*
-	 * Summary information.
-	 */
+	/* Summary information, filled by calculate_totals() */
 	uint64		total_size;		/* total size of the source cluster */
 	uint64		fetch_size;		/* number of bytes that needs to be copied */
-} filemap_t;
 
-extern filemap_t *filemap;
-
-extern void filemap_create(void);
-extern void calculate_totals(void);
-extern void print_filemap(void);
+	int			nactions;		/* size of 'actions' array */
+	file_entry_t *actions[FLEXIBLE_ARRAY_MEMBER];
+} filemap_t;
 
 /* Functions for populating the filemap */
+extern void filemap_init(void);
 extern void process_source_file(const char *path, file_type_t type,
 								size_t size, const char *link_target);
 extern void process_target_file(const char *path, file_type_t type,
@@ -116,6 +100,9 @@ extern void process_target_file(const char *path, file_type_t type,
 extern void process_target_wal_block_change(ForkNumber forknum,
 											RelFileNode rnode,
 											BlockNumber blkno);
-extern void filemap_finalize(void);
+
+extern filemap_t *filemap_finalize(void);
+extern void calculate_totals(filemap_t *filemap);
+extern void print_filemap(filemap_t *filemap);
 
 #endif							/* FILEMAP_H */
diff --git a/src/bin/pg_rewind/libpq_fetch.c b/src/bin/pg_rewind/libpq_fetch.c
index 7fc9161b8c8..9c541bb73d5 100644
--- a/src/bin/pg_rewind/libpq_fetch.c
+++ b/src/bin/pg_rewind/libpq_fetch.c
@@ -460,9 +460,9 @@ libpq_executeFileMap(filemap_t *map)
 				 PQresultErrorMessage(res));
 	PQclear(res);
 
-	for (i = 0; i < map->narray; i++)
+	for (i = 0; i < map->nactions; i++)
 	{
-		entry = map->array[i];
+		entry = map->actions[i];
 
 		/* If this is a relation file, copy the modified blocks */
 		execute_pagemap(&entry->target_modified_pages, entry->path);
diff --git a/src/bin/pg_rewind/pg_rewind.c b/src/bin/pg_rewind/pg_rewind.c
index 210984d302b..2bdeed26c53 100644
--- a/src/bin/pg_rewind/pg_rewind.c
+++ b/src/bin/pg_rewind/pg_rewind.c
@@ -129,6 +129,7 @@ main(int argc, char **argv)
 	TimeLineID	endtli;
 	ControlFileData ControlFile_new;
 	bool		writerecoveryconf = false;
+	filemap_t  *filemap;
 
 	pg_logging_init(argv[0]);
 	set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_rewind"));
@@ -371,10 +372,11 @@ main(int argc, char **argv)
 	/*
 	 * Collect information about all files in the target and source systems.
 	 */
-	filemap_create();
 	if (showprogress)
 		pg_log_info("reading source file list");
+	filemap_init();
 	fetchSourceFileList();
+
 	if (showprogress)
 		pg_log_info("reading target file list");
 	traverse_datadir(datadir_target, &process_target_file);
@@ -395,13 +397,13 @@ main(int argc, char **argv)
 	 * We have collected all information we need from both systems. Decide
 	 * what to do with each file.
 	 */
-	filemap_finalize();
+	filemap = filemap_finalize();
 	if (showprogress)
-		calculate_totals();
+		calculate_totals(filemap);
 
 	/* this is too verbose even for verbose mode */
 	if (debug)
-		print_filemap();
+		print_filemap(filemap);
 
 	/*
 	 * Ok, we're ready to start copying things over.
@@ -421,7 +423,7 @@ main(int argc, char **argv)
 	 * modified the target directory and there is no turning back!
 	 */
 
-	executeFileMap();
+	execute_file_actions(filemap);
 
 	progress_report(true);
 
-- 
2.20.1


--------------D93EDEBFB124D563B723F4BD
Content-Type: text/x-patch; charset=UTF-8;
 name="0004-pg_rewind-Refactor-the-abstraction-to-fetch-from-loc.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename*0="0004-pg_rewind-Refactor-the-abstraction-to-fetch-from-loc.pa";
 filename*1="tch"



^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: Fix inappropriate uses of atol()
@ 2024-08-03 14:07  Heikki Linnakangas <[email protected]>
  0 siblings, 1 reply; 3+ messages in thread

From: Heikki Linnakangas @ 2024-08-03 14:07 UTC (permalink / raw)
  To: Peter Eisentraut <[email protected]>; pgsql-hackers

On 03/08/2024 14:04, Peter Eisentraut wrote:
> I noticed (during [0]) to some uses of the function atol() seem 
> inappropriate.  Either they assume that sizeof(long)==8 and so might 
> truncate data if not, or they are gratuitous because the surrounding 
> code does not use the long type.  This patch fixes these, by using 
> atoll() or atoi() instead.  (There are still some atol() calls left 
> after this, which seemed ok to me.)
> 
> In the past, Windows didn't have atoll(), but the online documentation 
> appears to indicate that this now works in VS 2015 and later, which is 
> what we support at the moment.  The Cirrus CI passes.
+1 except for this one:

> diff --git a/src/interfaces/ecpg/preproc/ecpg.trailer b/src/interfaces/ecpg/preproc/ecpg.trailer
> index b2aa44f36dd..8ac1c5c9eda 100644
> --- a/src/interfaces/ecpg/preproc/ecpg.trailer
> +++ b/src/interfaces/ecpg/preproc/ecpg.trailer
> @@ -217,7 +217,7 @@ char_variable: cvariable
>  			enum ECPGttype type = p->type->type;
>  
>  			/* If we have just one character this is not a string */
> -			if (atol(p->type->size) == 1)
> +			if (atoi(p->type->size) == 1)
>  					mmerror(PARSE_ERROR, ET_ERROR, "invalid data type");
>  			else
>  			{
> 

In principle you can have an array larger than INT_MAX. However, this is 
a pretty weak test anyway. I think this is what the error is meant for:

EXEC SQL BEGIN DECLARE SECTION;
	char connstr;
EXEC SQL END DECLARE SECTION;
         EXEC SQL CONNECT TO :connstr;

This also produces the error, which seems fine:

EXEC SQL BEGIN DECLARE SECTION;
	char connstr[1];
EXEC SQL END DECLARE SECTION;
         EXEC SQL CONNECT TO :connstr;

This also produces the error, which does not seem good (if you replace 1 
with 2 here, it works):

EXEC SQL BEGIN DECLARE SECTION;
	char connstr[1+100];
EXEC SQL END DECLARE SECTION;
         EXEC SQL CONNECT TO :connstr;

You can work around that with:

#define LEN (1 + 100)
EXEC SQL BEGIN DECLARE SECTION;
	char connstr[LEN];
EXEC SQL END DECLARE SECTION;
         EXEC SQL CONNECT TO :connstr;

The grammar currently balks on arrays larger than INT_MAX, giving a 
"syntax error", which I don't think is correct, because at least my C 
compiler accepts it in a non-ecpg context:

EXEC SQL BEGIN DECLARE SECTION;
	char connstr[2147483648];
EXEC SQL END DECLARE SECTION;
         EXEC SQL CONNECT TO :connstr;

Overall I think we should just leave this as it is. If we want to do 
something here, would be good to address those cases that are currently 
bogus, but it's probably not worth the effort.

-- 
Heikki Linnakangas
Neon (https://neon.tech)







^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: Fix inappropriate uses of atol()
@ 2024-08-03 15:20  Tom Lane <[email protected]>
  parent: Heikki Linnakangas <[email protected]>
  0 siblings, 0 replies; 3+ messages in thread

From: Tom Lane @ 2024-08-03 15:20 UTC (permalink / raw)
  To: Heikki Linnakangas <[email protected]>; +Cc: Peter Eisentraut <[email protected]>; pgsql-hackers

Heikki Linnakangas <[email protected]> writes:
> On 03/08/2024 14:04, Peter Eisentraut wrote:
>> I noticed (during [0]) to some uses of the function atol() seem 
>> inappropriate.

> +1 except for this one:

>> /* If we have just one character this is not a string */
>> -			if (atol(p->type->size) == 1)
>> +			if (atoi(p->type->size) == 1)
>>  				mmerror(PARSE_ERROR, ET_ERROR, "invalid data type");

How about

-			if (atol(p->type->size) == 1)
+			if (strcmp(p->type->size, "1") == 0)

?  I've not actually tested, but this should catch the cases the
warning is meant to catch while not complaining about any of the
examples you give.  I'm not sure if leading/trailing spaces
would fool it (i.e., "char foo[ 1 ];").  But even if they do,
that doesn't seem disastrous.

			regards, tom lane






^ permalink  raw  reply  [nested|flat] 3+ messages in thread


end of thread, other threads:[~2024-08-03 15:20 UTC | newest]

Thread overview: 3+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2020-08-19 12:34 [PATCH 3/5] pg_rewind: Replace the hybrid list+array data structure with simplehash. Heikki Linnakangas <[email protected]>
2024-08-03 14:07 Re: Fix inappropriate uses of atol() Heikki Linnakangas <[email protected]>
2024-08-03 15:20 ` Re: Fix inappropriate uses of atol() Tom Lane <[email protected]>

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