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Write psql's ~/.psql_history file using history_truncate_file() and

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append_history(), if libreadline is new enough to have those functions
(they seem to be present at least since 4.2; but libedit may not have them).
This gives significantly saner behavior when two or more sessions overlap in
their use of the history file; although having two sessions exit at just the
same time is still perilous to your history.  The behavior of \s remains
unchanged, ie, overwrite whatever was there.
Per bug #5052 from Marek Wójtowicz.
This commit is contained in:
Tom Lane
2009-09-13 22:18:22 +00:00
parent eb62398f39
commit e97281c46c
7 changed files with 88 additions and 31 deletions
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92
src/bin/psql/input.c
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@@ -3,10 +3,15 @@
*
* Copyright (c) 2000-2009, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/bin/psql/input.c,v 1.66 2009/01/01 17:23:55 momjian Exp $
* $PostgreSQL: pgsql/src/bin/psql/input.c,v 1.67 2009/09/13 22:18:22 tgl Exp $
*/
#include "postgres_fe.h"
#ifndef WIN32
#include <unistd.h>
#endif
#include <fcntl.h>
#include "input.h"
#include "settings.h"
#include "tab-complete.h"
@@ -23,7 +28,11 @@
#ifdef USE_READLINE
static bool useReadline;
static bool useHistory;
char *psql_history;
static char *psql_history;
static int history_lines_added;
/*
* Preserve newlines in saved queries by mapping '\n' to NL_IN_HISTORY
@@ -135,6 +144,8 @@ pg_send_history(PQExpBuffer history_buf)
prev_hist = pg_strdup(s);
/* And send it to readline */
add_history(s);
/* Count lines added to history for use later */
history_lines_added++;
}
}
@@ -276,6 +287,7 @@ initializeInput(int flags)
useHistory = true;
using_history();
history_lines_added = 0;
histfile = GetVariable(pset.vars, "HISTFILE");
if (histfile == NULL)
@@ -310,15 +322,22 @@ initializeInput(int flags)
/*
* This function is for saving the readline history when user
* runs \s command or when psql finishes.
* This function saves the readline history when user
* runs \s command or when psql exits.
*
* We have an argument named encodeFlag to handle the cases differently.
* In case of call via \s we don't really need to encode \n as \x01,
* but when we save history for Readline we must do that conversion.
* fname: pathname of history file. (Should really be "const char *",
* but some ancient versions of readline omit the const-decoration.)
*
* max_lines: if >= 0, limit history file to that many entries.
*
* appendFlag: if true, try to append just our new lines to the file.
* If false, write the whole available history.
*
* encodeFlag: whether to encode \n as \x01. For \s calls we don't wish
* to do that, but must do so when saving the final history file.
*/
bool
saveHistory(char *fname, bool encodeFlag)
saveHistory(char *fname, int max_lines, bool appendFlag, bool encodeFlag)
{
#ifdef USE_READLINE
@@ -335,14 +354,54 @@ saveHistory(char *fname, bool encodeFlag)
encode_history();
/*
* return value of write_history is not standardized across GNU
* On newer versions of libreadline, truncate the history file as
* needed and then append what we've added. This avoids overwriting
* history from other concurrent sessions (although there are still
* race conditions when two sessions exit at about the same time).
* If we don't have those functions, fall back to write_history().
*
* Note: return value of write_history is not standardized across GNU
* readline and libedit. Therefore, check for errno becoming set to
* see if the write failed.
* see if the write failed. Similarly for append_history.
*/
errno = 0;
(void) write_history(fname);
if (errno == 0)
return true;
#if defined(HAVE_HISTORY_TRUNCATE_FILE) && defined(HAVE_APPEND_HISTORY)
if (appendFlag)
{
int nlines;
int fd;
/* truncate previous entries if needed */
if (max_lines >= 0)
{
nlines = Max(max_lines - history_lines_added, 0);
(void) history_truncate_file(fname, nlines);
}
/* append_history fails if file doesn't already exist :-( */
fd = open(fname, O_CREAT | O_WRONLY | PG_BINARY, 0600);
if (fd >= 0)
close(fd);
/* append the appropriate number of lines */
if (max_lines >= 0)
nlines = Min(max_lines, history_lines_added);
else
nlines = history_lines_added;
errno = 0;
(void) append_history(nlines, fname);
if (errno == 0)
return true;
}
else
#endif
{
/* truncate what we have ... */
if (max_lines >= 0)
stifle_history(max_lines);
/* ... and overwrite file. Tough luck for concurrent sessions. */
errno = 0;
(void) write_history(fname);
if (errno == 0)
return true;
}
psql_error("could not save history to file \"%s\": %s\n",
fname, strerror(errno));
@@ -369,10 +428,7 @@ finishInput(int exitstatus, void *arg)
int hist_size;
hist_size = GetVariableNum(pset.vars, "HISTSIZE", 500, -1, true);
if (hist_size >= 0)
stifle_history(hist_size);
saveHistory(psql_history, true);
saveHistory(psql_history, hist_size, true, true);
free(psql_history);
psql_history = NULL;
}