"Daniel Verite" <dan...@manitou-mail.org> writes:
> Tom Lane wrote:
>> One possible compromise that would address your concern about display
>> is to modify the hook API some more so that variable hooks could actually
>> substitute new values. Then for example the bool-variable hooks could
>> effectively replace "\set AUTOCOMMIT" by "\set AUTOCOMMIT on" and
>> "\unset AUTOCOMMIT" by "\set AUTOCOMMIT off", ensuring that interrogation
>> of their values always produces sane results.
> Agreed, that looks like a good compromise.
Attached is a draft patch for that. I chose to make a second hook rather
than complicate the assign hook API, mainly because it allows more code
sharing --- all the bool vars can share the same substitute hook, and
so can the three-way vars as long as "on" and "off" are the appropriate
substitutes.
I only touched the behavior for bool vars here, but if people like this
solution it could be fleshed out to apply to all the built-in variables.
Maybe we should merge SetVariableSubstituteHook and SetVariableAssignHook
into one function?
regards, tom lane
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 0574b5b..985cfcb 100644
*** a/src/bin/psql/startup.c
--- b/src/bin/psql/startup.c
*************** showVersion(void)
*** 777,787 ****
/*
! * Assign hooks for psql variables.
*
* This isn't an amazingly good place for them, but neither is anywhere else.
*/
static bool
autocommit_hook(const char *newval)
{
--- 777,804 ----
/*
! * Substitute hooks and assign hooks for psql variables.
*
* This isn't an amazingly good place for them, but neither is anywhere else.
*/
+ static char *
+ bool_substitute_hook(char *newval)
+ {
+ if (newval == NULL)
+ {
+ /* "\unset FOO" becomes "\set FOO off" */
+ newval = pg_strdup("off");
+ }
+ else if (newval[0] == '\0')
+ {
+ /* "\set FOO" becomes "\set FOO on" */
+ pg_free(newval);
+ newval = pg_strdup("on");
+ }
+ return newval;
+ }
+
static bool
autocommit_hook(const char *newval)
{
*************** EstablishVariableSpace(void)
*** 1002,1015 ****
--- 1019,1039 ----
{
pset.vars = CreateVariableSpace();
+ SetVariableSubstituteHook(pset.vars, "AUTOCOMMIT", bool_substitute_hook);
SetVariableAssignHook(pset.vars, "AUTOCOMMIT", autocommit_hook);
+ SetVariableSubstituteHook(pset.vars, "ON_ERROR_STOP", bool_substitute_hook);
SetVariableAssignHook(pset.vars, "ON_ERROR_STOP", on_error_stop_hook);
+ SetVariableSubstituteHook(pset.vars, "QUIET", bool_substitute_hook);
SetVariableAssignHook(pset.vars, "QUIET", quiet_hook);
+ SetVariableSubstituteHook(pset.vars, "SINGLELINE", bool_substitute_hook);
SetVariableAssignHook(pset.vars, "SINGLELINE", singleline_hook);
+ SetVariableSubstituteHook(pset.vars, "SINGLESTEP", bool_substitute_hook);
SetVariableAssignHook(pset.vars, "SINGLESTEP", singlestep_hook);
SetVariableAssignHook(pset.vars, "FETCH_COUNT", fetch_count_hook);
SetVariableAssignHook(pset.vars, "ECHO", echo_hook);
+ SetVariableSubstituteHook(pset.vars, "ECHO_HIDDEN", bool_substitute_hook);
SetVariableAssignHook(pset.vars, "ECHO_HIDDEN", echo_hidden_hook);
+ SetVariableSubstituteHook(pset.vars, "ON_ERROR_ROLLBACK", bool_substitute_hook);
SetVariableAssignHook(pset.vars, "ON_ERROR_ROLLBACK", on_error_rollback_hook);
SetVariableAssignHook(pset.vars, "COMP_KEYWORD_CASE", comp_keyword_case_hook);
SetVariableAssignHook(pset.vars, "HISTCONTROL", histcontrol_hook);
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index 91e4ae8..61c4ccc 100644
*** a/src/bin/psql/variables.c
--- b/src/bin/psql/variables.c
*************** CreateVariableSpace(void)
*** 52,57 ****
--- 52,58 ----
ptr = pg_malloc(sizeof *ptr);
ptr->name = NULL;
ptr->value = NULL;
+ ptr->substitute_hook = NULL;
ptr->assign_hook = NULL;
ptr->next = NULL;
*************** ParseVariableBool(const char *value, con
*** 101,111 ****
size_t len;
bool valid = true;
if (value == NULL)
! {
! *result = false; /* not set -> assume "off" */
! return valid;
! }
len = strlen(value);
--- 102,110 ----
size_t len;
bool valid = true;
+ /* Treat "unset" as an empty string, which will lead to error below */
if (value == NULL)
! value = "";
len = strlen(value);
*************** ParseVariableNum(const char *value, cons
*** 152,159 ****
char *end;
long numval;
if (value == NULL)
! return false;
errno = 0;
numval = strtol(value, &end, 0);
if (errno == 0 && *end == '\0' && end != value && numval == (int) numval)
--- 151,160 ----
char *end;
long numval;
+ /* Treat "unset" as an empty string, which will lead to error below */
if (value == NULL)
! value = "";
!
errno = 0;
numval = strtol(value, &end, 0);
if (errno == 0 && *end == '\0' && end != value && numval == (int) numval)
*************** SetVariable(VariableSpace space, const c
*** 235,247 ****
if (!valid_variable_name(name))
{
psql_error("invalid variable name: \"%s\"\n", name);
return false;
}
- if (!value)
- return DeleteVariable(space, name);
-
for (previous = space, current = space->next;
current;
previous = current, current = current->next)
--- 236,248 ----
if (!valid_variable_name(name))
{
+ /* Deletion of non-existent variable is not an error */
+ if (!value)
+ return true;
psql_error("invalid variable name: \"%s\"\n", name);
return false;
}
for (previous = space, current = space->next;
current;
previous = current, current = current->next)
*************** SetVariable(VariableSpace space, const c
*** 249,262 ****
if (strcmp(current->name, name) == 0)
{
/*
! * Found entry, so update, unless hook returns false. The hook
! * may need the passed value to have the same lifespan as the
! * variable, so allocate it right away, even though we'll have to
! * free it again if the hook returns false.
*/
! char *new_value = pg_strdup(value);
bool confirmed;
if (current->assign_hook)
confirmed = (*current->assign_hook) (new_value);
else
--- 250,269 ----
if (strcmp(current->name, name) == 0)
{
/*
! * Found entry, so update, unless assign hook returns false.
! *
! * We must duplicate the passed value to start with. This
! * simplifies the API for substitute hooks. Moreover, some assign
! * hooks assume that the passed value has the same lifespan as the
! * variable. Having to free the string again on failure is a
! * small price to pay for keeping these APIs simple.
*/
! char *new_value = value ? pg_strdup(value) : NULL;
bool confirmed;
+ if (current->substitute_hook)
+ new_value = (*current->substitute_hook) (new_value);
+
if (current->assign_hook)
confirmed = (*current->assign_hook) (new_value);
else
*************** SetVariable(VariableSpace space, const c
*** 267,288 ****
if (current->value)
pg_free(current->value);
current->value = new_value;
}
! else
pg_free(new_value); /* current->value is left unchanged */
return confirmed;
}
}
/* not present, make new entry */
current = pg_malloc(sizeof *current);
current->name = pg_strdup(name);
! current->value = pg_strdup(value);
current->assign_hook = NULL;
current->next = NULL;
previous->next = current;
! return true;
}
/*
--- 274,358 ----
if (current->value)
pg_free(current->value);
current->value = new_value;
+
+ /*
+ * If we deleted the value, and there are no hooks to
+ * remember, we can discard the variable altogether.
+ */
+ if (new_value == NULL &&
+ current->substitute_hook == NULL &&
+ current->assign_hook == NULL)
+ {
+ previous->next = current->next;
+ free(current->name);
+ free(current);
+ }
}
! else if (new_value)
pg_free(new_value); /* current->value is left unchanged */
return confirmed;
}
}
+ /* not present, make new entry ... unless we were asked to delete */
+ if (value)
+ {
+ current = pg_malloc(sizeof *current);
+ current->name = pg_strdup(name);
+ current->value = pg_strdup(value);
+ current->substitute_hook = NULL;
+ current->assign_hook = NULL;
+ current->next = NULL;
+ previous->next = current;
+ }
+ return true;
+ }
+
+ /*
+ * Attach a substitute hook function to the named variable.
+ *
+ * If the variable doesn't already exist, create it with value NULL,
+ * just so we have a place to store the hook function. (But the hook
+ * might immediately change the NULL to something else.)
+ *
+ * The hook is immediately called on the variable's current value.
+ */
+ void
+ SetVariableSubstituteHook(VariableSpace space, const char *name,
+ VariableSubstituteHook hook)
+ {
+ struct _variable *current,
+ *previous;
+
+ if (!space || !name)
+ return;
+
+ if (!valid_variable_name(name))
+ return;
+
+ for (previous = space, current = space->next;
+ current;
+ previous = current, current = current->next)
+ {
+ if (strcmp(current->name, name) == 0)
+ {
+ /* found entry, so update */
+ current->substitute_hook = hook;
+ current->value = (*hook) (current->value);
+ return;
+ }
+ }
+
/* not present, make new entry */
current = pg_malloc(sizeof *current);
current->name = pg_strdup(name);
! current->value = NULL;
! current->substitute_hook = hook;
current->assign_hook = NULL;
current->next = NULL;
previous->next = current;
! current->value = (*hook) (current->value);
}
/*
*************** SetVariable(VariableSpace space, const c
*** 299,305 ****
* get called before any user-supplied value is assigned.
*/
void
! SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook)
{
struct _variable *current,
*previous;
--- 369,376 ----
* get called before any user-supplied value is assigned.
*/
void
! SetVariableAssignHook(VariableSpace space, const char *name,
! VariableAssignHook hook)
{
struct _variable *current,
*previous;
*************** SetVariableAssignHook(VariableSpace spac
*** 327,332 ****
--- 398,404 ----
current = pg_malloc(sizeof *current);
current->name = pg_strdup(name);
current->value = NULL;
+ current->substitute_hook = NULL;
current->assign_hook = hook;
current->next = NULL;
previous->next = current;
*************** SetVariableBool(VariableSpace space, con
*** 351,392 ****
bool
DeleteVariable(VariableSpace space, const char *name)
{
! struct _variable *current,
! *previous;
!
! if (!space)
! return true;
!
! for (previous = space, current = space->next;
! current;
! previous = current, current = current->next)
! {
! if (strcmp(current->name, name) == 0)
! {
! if (current->assign_hook)
! {
! /* Allow deletion only if hook is okay with NULL value */
! if (!(*current->assign_hook) (NULL))
! return false; /* message printed by hook */
! if (current->value)
! free(current->value);
! current->value = NULL;
! /* Don't delete entry, or we'd forget the hook function */
! }
! else
! {
! /* We can delete the entry as well as its value */
! if (current->value)
! free(current->value);
! previous->next = current->next;
! free(current->name);
! free(current);
! }
! return true;
! }
! }
!
! return true;
}
/*
--- 423,429 ----
bool
DeleteVariable(VariableSpace space, const char *name)
{
! return SetVariable(space, name, NULL);
}
/*
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index 274b4af..f382bfd 100644
*** a/src/bin/psql/variables.h
--- b/src/bin/psql/variables.h
***************
*** 18,45 ****
* prevent invalid values from being assigned, and can update internal C
* variables to keep them in sync with the variable's current value.
*
! * A hook function is called before any attempted assignment, with the
* proposed new value of the variable (or with NULL, if an \unset is being
* attempted). If it returns false, the assignment doesn't occur --- it
* should print an error message with psql_error() to tell the user why.
*
! * When a hook function is installed with SetVariableAssignHook(), it is
! * called with the variable's current value (or with NULL, if it wasn't set
* yet). But its return value is ignored in this case. The hook should be
* set before any possibly-invalid value can be assigned.
*/
typedef bool (*VariableAssignHook) (const char *newval);
/*
* Data structure representing one variable.
*
* Note: if value == NULL then the variable is logically unset, but we are
! * keeping the struct around so as not to forget about its hook function.
*/
struct _variable
{
char *name;
char *value;
VariableAssignHook assign_hook;
struct _variable *next;
};
--- 18,70 ----
* prevent invalid values from being assigned, and can update internal C
* variables to keep them in sync with the variable's current value.
*
! * An assign hook function is called before any attempted assignment, with the
* proposed new value of the variable (or with NULL, if an \unset is being
* attempted). If it returns false, the assignment doesn't occur --- it
* should print an error message with psql_error() to tell the user why.
*
! * When an assign hook function is installed with SetVariableAssignHook(), it
! * is called with the variable's current value (or with NULL, if it wasn't set
* yet). But its return value is ignored in this case. The hook should be
* set before any possibly-invalid value can be assigned.
*/
typedef bool (*VariableAssignHook) (const char *newval);
/*
+ * Variables can also be given "substitute hook" functions. The substitute
+ * hook can replace values (including NULL) with other values, allowing
+ * normalization of variable contents. For example, for a boolean variable,
+ * we wish to interpret "\unset FOO" as "\set FOO off", and we can do that
+ * by installing a substitute hook. (We can use the same substitute hook
+ * for all bool or nearly-bool variables, which is why this responsibility
+ * isn't part of the assign hook.)
+ *
+ * The substitute hook is called before any attempted assignment, and before
+ * the assign hook if any, passing the proposed new value of the variable as a
+ * malloc'd string (or NULL, if an \unset is being attempted). It can return
+ * the same value, or a different malloc'd string, or modify the string
+ * in-place. It should free the passed-in value if it's not returning it.
+ * The substitute hook generally should not complain about erroneous values;
+ * that's a job for the assign hook.
+ *
+ * When a substitute hook is installed with SetVariableSubstituteHook(),
+ * it is applied to the variable's current value (typically NULL, if it wasn't
+ * set yet). It's usually best to do that before installing the assign hook
+ * if there is one.
+ */
+ typedef char *(*VariableSubstituteHook) (char *newval);
+
+ /*
* Data structure representing one variable.
*
* Note: if value == NULL then the variable is logically unset, but we are
! * keeping the struct around so as not to forget about its hook function(s).
*/
struct _variable
{
char *name;
char *value;
+ VariableSubstituteHook substitute_hook;
VariableAssignHook assign_hook;
struct _variable *next;
};
*************** int GetVariableNum(VariableSpace space,
*** 65,70 ****
--- 90,96 ----
void PrintVariables(VariableSpace space);
bool SetVariable(VariableSpace space, const char *name, const char *value);
+ void SetVariableSubstituteHook(VariableSpace space, const char *name, VariableSubstituteHook hook);
void SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook);
bool SetVariableBool(VariableSpace space, const char *name);
bool DeleteVariable(VariableSpace space, const char *name);
diff --git a/src/test/regress/expected/psql.out b/src/test/regress/expected/psql.out
index 420825a..026a4f0 100644
*** a/src/test/regress/expected/psql.out
--- b/src/test/regress/expected/psql.out
*************** invalid variable name: "invalid/name"
*** 11,16 ****
--- 11,33 ----
unrecognized value "foo" for "AUTOCOMMIT": boolean expected
\set FETCH_COUNT foo
invalid value "foo" for "FETCH_COUNT": integer expected
+ -- check handling of built-in boolean variable
+ \echo :ON_ERROR_ROLLBACK
+ off
+ \set ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \set ON_ERROR_ROLLBACK foo
+ unrecognized value "foo" for "ON_ERROR_ROLLBACK"
+ Available values are: on, off, interactive.
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \set ON_ERROR_ROLLBACK on
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \unset ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ off
-- \gset
select 10 as test01, 20 as test02, 'Hello' as test03 \gset pref01_
\echo :pref01_test01 :pref01_test02 :pref01_test03
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index 79624b9..d823d11 100644
*** a/src/test/regress/sql/psql.sql
--- b/src/test/regress/sql/psql.sql
***************
*** 10,15 ****
--- 10,25 ----
-- fail: invalid value for special variable
\set AUTOCOMMIT foo
\set FETCH_COUNT foo
+ -- check handling of built-in boolean variable
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK foo
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK on
+ \echo :ON_ERROR_ROLLBACK
+ \unset ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
-- \gset
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