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Fix pg_dump to read-lock all tables to be dumped as soon as it's read

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their names from pg_class.  This considerably reduces the window wherein
someone could DROP or ALTER a table that pg_dump is intending to dump.
Not a perfect solution, but definitely an improvement.  Per complaints
from Marc Fournier; patch by Brent Verner with some kibitzing by Tom Lane.
REL7_2_STABLE
Tom Lane 24 years ago
parent 5c2d36c3dd
commit 0e1a5075fd
3 changed files with 74 additions and 21 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 4
      src/bin/pg_dump/common.c
  2. 82
      src/bin/pg_dump/pg_dump.c
  3. 9
      src/bin/pg_dump/pg_dump.h

4
src/bin/pg_dump/common.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/bin/pg_dump/common.c,v 1.60 2001/10/25 05:49:52 momjian Exp $
* $Header: /cvsroot/pgsql/src/bin/pg_dump/common.c,v 1.61 2002/01/11 23:21:55 tgl Exp $
*
* Modifications - 6/12/96 - dave@bensoft.com - version 1.13.dhb.2
*
@ -309,7 +309,7 @@ dumpSchema(Archive *fout,
if (g_verbose)
write_msg(NULL, "reading user-defined tables\n");
tblinfo = getTables(&numTables, finfo, numFuncs);
tblinfo = getTables(&numTables, finfo, numFuncs, tablename);
if (g_verbose)
write_msg(NULL, "reading index information\n");

82
src/bin/pg_dump/pg_dump.c
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@ -22,7 +22,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/bin/pg_dump/pg_dump.c,v 1.236 2001/10/28 06:25:58 momjian Exp $
* $Header: /cvsroot/pgsql/src/bin/pg_dump/pg_dump.c,v 1.237 2002/01/11 23:21:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -2035,13 +2035,14 @@ getFuncs(int *numFuncs)
* numTables is set to the number of tables read in
*/
TableInfo *
getTables(int *numTables, FuncInfo *finfo, int numFuncs)
getTables(int *numTables, FuncInfo *finfo, int numFuncs, const char* tablename)
{
PGresult *res;
int ntups;
int i;
PQExpBuffer query = createPQExpBuffer();
PQExpBuffer delqry = createPQExpBuffer();
PQExpBuffer lockquery = createPQExpBuffer();
TableInfo *tblinfo;
int i_reloid;
@ -2054,11 +2055,6 @@ getTables(int *numTables, FuncInfo *finfo, int numFuncs)
int i_relhasindex;
int i_relhasoids;
char relkindview[2];
relkindview[0] = RELKIND_VIEW;
relkindview[1] = '\0';
/*
* find all the user-defined tables (no indexes and no catalogs),
* ordering by oid is important so that we always process the parent
@ -2129,6 +2125,17 @@ getTables(int *numTables, FuncInfo *finfo, int numFuncs)
*numTables = ntups;
/*
* First pass: extract data from result and lock tables. We do the
* locking before anything else, to minimize the window wherein a table
* could disappear under us.
*
* Note that we have to collect info about all tables here, even when
* dumping only one, because we don't know which tables might be
* inheritance ancestors of the target table. Possible future
* improvement: suppress later collection of schema info about tables
* that are determined not to be either targets or ancestors of targets.
*/
tblinfo = (TableInfo *) malloc(ntups * sizeof(TableInfo));
i_reloid = PQfnumber(res, "oid");
@ -2146,17 +2153,63 @@ getTables(int *numTables, FuncInfo *finfo, int numFuncs)
tblinfo[i].oid = strdup(PQgetvalue(res, i, i_reloid));
tblinfo[i].relname = strdup(PQgetvalue(res, i, i_relname));
tblinfo[i].relacl = strdup(PQgetvalue(res, i, i_relacl));
tblinfo[i].sequence = (strcmp(PQgetvalue(res, i, i_relkind), "S") == 0);
tblinfo[i].relkind = *(PQgetvalue(res, i, i_relkind));
tblinfo[i].sequence = (tblinfo[i].relkind == RELKIND_SEQUENCE);
tblinfo[i].hasindex = (strcmp(PQgetvalue(res, i, i_relhasindex), "t") == 0);
tblinfo[i].hasoids = (strcmp(PQgetvalue(res, i, i_relhasoids), "t") == 0);
tblinfo[i].usename = strdup(PQgetvalue(res, i, i_usename));
tblinfo[i].ncheck = atoi(PQgetvalue(res, i, i_relchecks));
tblinfo[i].ntrig = atoi(PQgetvalue(res, i, i_reltriggers));
/*
* Read-lock target tables to make sure they aren't DROPPED or
* altered in schema before we get around to dumping them.
*
* If no target tablename was specified, lock all tables we see,
* otherwise lock only the specified table. (This is incomplete
* because we'll still try to collect schema info about all tables,
* and could possibly lose during that phase. But for the typical
* use where we're dumping all tables anyway, it matters not.)
*
* NOTE: it'd be kinda nice to lock views and sequences too, not
* only plain tables, but the backend doesn't presently allow that.
*/
if ((tblinfo[i].relkind == RELKIND_RELATION) &&
(tablename == NULL || strcmp(tblinfo[i].relname, tablename) == 0))
{
PGresult *lres;
resetPQExpBuffer(lockquery);
appendPQExpBuffer(lockquery,
"LOCK TABLE %s IN ACCESS SHARE MODE",
fmtId(tblinfo[i].relname, force_quotes));
lres = PQexec(g_conn,lockquery->data);
if (!lres || PQresultStatus(lres) != PGRES_COMMAND_OK)
{
write_msg(NULL, "Attempt to lock table \"%s\" failed. %s",
tblinfo[i].relname, PQerrorMessage(g_conn));
exit_nicely();
}
PQclear(lres);
}
}
PQclear(res);
res = NULL;
/*
* Second pass: pick up additional information about each table,
* as required.
*/
for (i = 0; i < *numTables; i++)
{
/* Emit notice if join for owner failed */
if (strlen(tblinfo[i].usename) == 0)
write_msg(NULL, "WARNING: owner of table \"%s\" appears to be invalid\n",
tblinfo[i].relname);
/* Get view definition */
if (strcmp(PQgetvalue(res, i, i_relkind), relkindview) == 0)
/* Get definition if it's a view */
if (tblinfo[i].relkind == RELKIND_VIEW)
{
PGresult *res2;
@ -2208,6 +2261,7 @@ getTables(int *numTables, FuncInfo *finfo, int numFuncs)
tblinfo[i].relname);
exit_nicely();
}
PQclear(res2);
}
else
tblinfo[i].viewdef = NULL;
@ -2291,7 +2345,7 @@ getTables(int *numTables, FuncInfo *finfo, int numFuncs)
tblinfo[i].check_expr = NULL;
/* Get primary key */
if (strcmp(PQgetvalue(res, i, i_relhasindex), "t") == 0)
if (tblinfo[i].hasindex)
{
PGresult *res2;
@ -2323,9 +2377,6 @@ getTables(int *numTables, FuncInfo *finfo, int numFuncs)
else
tblinfo[i].pkIndexOid = NULL;
/* Has it got OIDs? */
tblinfo[i].hasoids = (strcmp(PQgetvalue(res, i, i_relhasoids), "t") == 0);
/* Get primary key name (if primary key exist) */
if (tblinfo[i].pkIndexOid != NULL)
{
@ -2643,10 +2694,9 @@ getTables(int *numTables, FuncInfo *finfo, int numFuncs)
}
PQclear(res);
destroyPQExpBuffer(query);
destroyPQExpBuffer(delqry);
destroyPQExpBuffer(lockquery);
return tblinfo;
}

9
src/bin/pg_dump/pg_dump.h
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@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: pg_dump.h,v 1.76 2001/11/05 17:46:30 momjian Exp $
* $Id: pg_dump.h,v 1.77 2002/01/11 23:21:55 tgl Exp $
*
* Modifications - 6/12/96 - dave@bensoft.com - version 1.13.dhb.2
*
@ -96,7 +96,9 @@ typedef struct _tableInfo
* constructed manually from rules, and
* rule may ref things created after the
* base table was created. */
bool sequence;
char relkind;
bool sequence; /* this is redundant with relkind... */
bool hasindex; /* does it have any indexes? */
bool hasoids; /* does it have OIDs? */
int numatts; /* number of attributes */
int *inhAttrs; /* an array of flags, one for each
@ -254,7 +256,8 @@ extern void clearOprInfo(OprInfo *, int);
extern void clearTypeInfo(TypeInfo *, int);
extern OprInfo *getOperators(int *numOperators);
extern TableInfo *getTables(int *numTables, FuncInfo *finfo, int numFuncs);
extern TableInfo *getTables(int *numTables, FuncInfo *finfo, int numFuncs,
const char* tablename);
extern InhInfo *getInherits(int *numInherits);
extern void getTableAttrs(TableInfo *tbinfo, int numTables);
extern IndInfo *getIndexes(int *numIndexes);

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