Allow commenting of variables in postgresql.conf to restore them to defaults

There is path implements following item from todo list: "Allow
commenting of variables in postgresql.conf to restore them to defaults".
Main idea is:

General config structure is extend with default_val attribute to keep
really default value. (There is small conflict - for string boot_val has same meaning).
During reconfiguration all values which has reset source equal with
PGC_S_FILE are revert back to really default values. New values from
configuration files are set after this step and commented variables stay
with default value.

Zdenek



Index: src/backend/utils/misc/guc-file.l

===================================================================

RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/guc-file.l,v

retrieving revision 1.37

diff -r1.37 guc-file.l

115c115

<     int            elevel;

---

>     int            elevel, i;

116a117

>     char       *env;

145a147,182

>     /* Revert all options with reset source PGC_S_FILE to default value.

>      * This implementation is easier then implementing some change flag and verify

>      * what really was commented out.

>      * XXX When log_line_prefix is set in configuration file then log output

>      * is not correct during this phase - prefix is revert to empty value.

>      */

>     for (i = 0; i < num_guc_variables; i++)

>     {

>         struct config_generic *gconf = guc_variables[i];

>         if ( gconf->reset_source == PGC_S_FILE )

>         {

>             set_config_option(gconf->name, NULL, context,

>                   PGC_S_FILE, false, true);

>         }

>     }

>

>     /* Revert to environment variable. PGPORT is ignored, because it cannot be

>      * set in running state. PGC_S_FILE is used instead PGC_S_ENV so as

>      * set_config_option can override previous defined option in config file.

>      * If these options are still in config file They will be overridden in

>      * the following step.

>      */

>     env = getenv("PGDATESTYLE");

>     if (env != NULL)

>     {

>         set_config_option("datestyle", env, context,

>                             PGC_S_FILE, false, true);

>     }

>

>     env = getenv("PGCLIENTENCODING");

>     if (env != NULL)

>     {

>         set_config_option("client_encoding", env, context,

>                             PGC_S_FILE, false, true);

>     }

>

Index: src/backend/utils/misc/guc.c

===================================================================

RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/guc.c,v

retrieving revision 1.319

diff -r1.319 guc.c

2651c2651

<                         if (!(*conf->assign_hook) (conf->reset_val, true,

---

>                         if (!(*conf->assign_hook) (conf->default_val, true,

2654,2655c2654,2655

<                                  conf->gen.name, (int) conf->reset_val);

<                     *conf->variable = conf->reset_val;

---

>                                  conf->gen.name, (int) conf->default_val);

>                     *conf->variable = conf->reset_val = conf->default_val;

2665c2665

<                         if (!(*conf->assign_hook) (conf->reset_val, true,

---

>                         if (!(*conf->assign_hook) (conf->default_val, true,

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<                                  conf->gen.name, conf->reset_val);

<                     *conf->variable = conf->reset_val;

---

>                                  conf->gen.name, conf->default_val);

>                     *conf->variable = conf->reset_val = conf->default_val;

2679c2679

<                         if (!(*conf->assign_hook) (conf->reset_val, true,

---

>                         if (!(*conf->assign_hook) (conf->default_val, true,

2682,2683c2682,2683

<                                  conf->gen.name, conf->reset_val);

<                     *conf->variable = conf->reset_val;

---

>                                  conf->gen.name, conf->default_val);

>                     *conf->variable = conf->reset_val = conf->default_val;

3650c3650

<                 if (changeVal && !is_newvalue_equal(record, value))

---

>                 if (changeVal && value != NULL && !is_newvalue_equal(record, value))

3726c3726

<     makeDefault = changeVal && (source <= PGC_S_OVERRIDE) && (value != NULL);

---

>     makeDefault = changeVal && (source <= PGC_S_OVERRIDE) && (value != NULL || source == PGC_S_FILE);

3769,3770c3769,3781

<                     newval = conf->reset_val;

<                     source = conf->gen.reset_source;

---

>                     /* Revert value to default if source is configuration file. It is used when

>                      * configuration parameter is removed/commented out in the config file. Else

>                      * RESET or SET TO DEFAULT command is called and reset_val is used.

>                      */

>                     if( source == PGC_S_FILE )

>                     {

>                         newval =  conf->default_val;

>                     }

>                     else

>                     {

>                         newval = conf->reset_val;

>                         source = conf->gen.reset_source;

>                     }

3853,3854c3864,3876

<                     newval = conf->reset_val;

<                     source = conf->gen.reset_source;

---

>                     /* Revert value to default if source is configuration file. It is used when

>                      * configuration parameter is removed/commented out in the config file. Else

>                      * RESET or SET TO DEFAULT command is called and reset_val is used.

>                      */

>                     if( source == PGC_S_FILE )

>                     {

>                         newval =  conf->default_val;

>                     }

>                     else

>                     {

>                         newval = conf->reset_val;

>                         source = conf->gen.reset_source;

>                     }

3937,3938c3959,3971

<                     newval = conf->reset_val;

<                     source = conf->gen.reset_source;

---

>                     /* Revert value to default if source is configuration file. It is used when

>                      * configuration parameter is removed/commented out in the config file. Else

>                      * RESET or SET TO DEFAULT command is called and reset_val is used.

>                      */

>                     if( source == PGC_S_FILE )

>                     {

>                         newval =  conf->default_val;

>                     }

>                     else

>                     {

>                         newval = conf->reset_val;

>                         source = conf->gen.reset_source;

>                     }

4011a4045,4058

>                 else if (source == PGC_S_FILE)

>                 {

>                     /* Revert value to default when item is removed from config file. */

>                     if ( conf->boot_val != NULL )

>                     {

>                         newval = guc_strdup(elevel, conf->boot_val);

>                         if (newval == NULL)

>                             return false;

>                     }

>                     else

>                     {

>                         return false;

>                     }

>                 }

5113a5161,5165

>     if( !newvalue )

>     {

>         return false;

>     }

>

Index: src/include/utils/guc_tables.h

===================================================================

RCS file: /projects/cvsroot/pgsql/src/include/utils/guc_tables.h,v

retrieving revision 1.22

diff -r1.22 guc_tables.h

145c145

<     bool        reset_val;

---

>     bool        default_val;

149a150

>     bool        reset_val;

158c159

<     int            reset_val;

---

>     int            default_val;

164a166

>     int            reset_val;

173c175

<     double        reset_val;

---

>     double        default_val;

179a182,183

>       double        reset_val;

>