>
>
> Fabien is pressed for time, so I've been speaking with him out-of-thread
> about how I should go about implementing it.
>
> The v1 patch will be \if <expr>, \elseif <expr>, \else, \endif, where
> <expr> will be naively evaluated via ParseVariableBool().
>
> \ifs and \endifs must be in the same "file" (each MainLoop will start a
> new if-stack). This is partly for sanity (you can see the pairings unless
> the programmer is off in \gset meta-land), partly for ease of design (data
> structures live in MainLoop), but mostly because it would an absolute
> requirement if we ever got around to doing \while.
>
> I hope to have something ready for the next commitfest.
>
> As for the fate of \quit_if, I can see it both ways. On the one hand,
> it's super-simple, already written, and handy.
>
> On the other hand, it's easily replaced by
>
> \if <expr>
> \q
> \endif
>
>
> So I'll leave that as a separate reviewable patch.
>
> As for loops, I don't think anyone was pushing for implementing \while
> now, only to have a decision about what it would look like and how it would
> work. There's a whole lot of recording infrastructure (the input could be a
> stream) needed to make it happen. Moreover, I think \gexec scratched a
> lot of the itches that would have been solved via a psql looping structure.
>
And here's the patch. I've changed the subject line and will be submitting
a new entry to the commitfest.
diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 9915731..2c3fccd 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -2007,6 +2007,83 @@ hello 10
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><literal>\if</literal> <replaceable
class="parameter">expr</replaceable></term>
+ <term><literal>\elseif</literal> <replaceable
class="parameter">expr</replaceable></term>
+ <term><literal>\else</literal></term>
+ <term><literal>\endif</literal></term>
+ <listitem>
+ <para>
+ This group of commands implements nestable conditional blocks, like
+ this:
+ </para>
+<programlisting>
+\if true
+ \if 1
+ \if yes
+ \if on
+ \echo 'all true'
+all true
+ \endif
+ \endif
+ \endif
+\endif
+\if false
+\elseif 0
+\elseif no
+\elseif off
+\else
+ \echo 'all false'
+all false
+\endif
+\if true
+\else
+ \echo 'should not print #1'
+\endif
+\if false
+\elseif true
+\else
+ \echo 'should not print #2'
+\endif
+</programlisting>
+ <para>
+ Conditional blocks must begin with a <command>\if</command> and end
+ with an <command>\endif</command>, and the pairs must be found in
+ the same source file. If an EOF is reached on the main file or an
+ <command>\include</command>-ed file before all
+ <command>\if</command>-<command>\endif</command> are matched, then
+ psql will raise an error.
+ </para>
+ <para>
+ The <command>\if</command> and <command>\elseif</command> commands
+ read the rest of the line and evaluate it as a boolean expression.
+ Currently, expressions are limited to the same values allowed for
+ other option booleans (true, false, 1, 0, on, off, yes, no, etc).
+ </para>
+ <para>
+ Queries within a false branch of a conditional block will not be
+ sent to the server.
+ </para>
+ <para>
+ Non-conditional <command>\</command>-commands within a false branch
+ of a conditional block will not be evaluated for correctness. The
+ command will be ignored along with all remaining input to the end
+ of the line.
+ </para>
+ <para>
+ Expressions on <command>\if</command> and <command>\elseif</command>
+ commands within a false branch of a conditional block will not be
+ evaluated.
+ </para>
+ <para>
+ A conditional block can at most one <command>\else</command> command.
+ </para>
+ <para>
+ The <command>\elseif</command> command cannot follow the
+ <command>\else</command> command.
+ </para>
+ </listitem>
+ </varlistentry>
<varlistentry>
<term><literal>\ir</literal> or <literal>\include_relative</literal>
<replaceable class="parameter">filename</replaceable></term>
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 4139b77..d4e0bb8 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -49,6 +49,7 @@
#include "psqlscanslash.h"
#include "settings.h"
#include "variables.h"
+#include "fe_utils/psqlscan_int.h"
/*
* Editable database object types.
@@ -132,7 +133,7 @@ HandleSlashCmds(PsqlScanState scan_state,
status = PSQL_CMD_ERROR;
}
- if (status != PSQL_CMD_ERROR)
+ if ((status != PSQL_CMD_ERROR) && psqlscan_branch_active(scan_state))
{
/* eat any remaining arguments after a valid command */
/* note we suppress evaluation of backticks here */
@@ -194,6 +195,32 @@ read_connect_arg(PsqlScanState scan_state)
return result;
}
+/*
+ * Read and interpret argument as a boolean expression.
+ */
+static bool
+read_boolean_expression(PsqlScanState scan_state, const char *action)
+{
+ bool result = false;
+ char *expr = psql_scan_slash_option(scan_state,
+
OT_NORMAL, NULL, false);
+ if (expr)
+ {
+ if (ParseVariableBool(expr, action))
+ result = true;
+ free(expr);
+ }
+ return result;
+}
+
+static bool
+is_branching_command(const char *cmd)
+{
+ return ((strcmp(cmd, "if") == 0 || \
+ strcmp(cmd, "elseif") == 0 || \
+ strcmp(cmd, "else") == 0 || \
+ strcmp(cmd, "endif") == 0));
+}
/*
* Subroutine to actually try to execute a backslash command.
@@ -207,6 +234,14 @@ exec_command(const char *cmd,
* failed */
backslashResult status = PSQL_CMD_SKIP_LINE;
+ if (!psqlscan_branch_active(scan_state) && !is_branching_command(cmd) )
+ {
+ /* Continue with an empty buffer as if the command were never
read */
+ resetPQExpBuffer(query_buf); /* TODO: is this needed? */
+ psql_scan_reset(scan_state); /* TODO: is this needed or just
for interactive? */
+ return status;
+ }
+
/*
* \a -- toggle field alignment This makes little sense but we keep it
* around.
@@ -984,6 +1019,84 @@ exec_command(const char *cmd,
}
}
+ else if (strcmp(cmd, "if") == 0)
+ {
+ ifState new_if_state = IFSTATE_IGNORED;
+ if (psqlscan_branch_active(scan_state))
+ {
+ if (read_boolean_expression(scan_state, "\\if"))
+ new_if_state = IFSTATE_TRUE;
+ else
+ new_if_state = IFSTATE_FALSE;
+ }
+ psqlscan_branch_push(scan_state,new_if_state);
+ psql_scan_reset(scan_state);
+ }
+
+ else if (strcmp(cmd, "elseif") == 0)
+ {
+ if (psqlscan_branch_empty(scan_state))
+ psql_error("encountered un-matched \\elseif\n");
+
+ switch (psqlscan_branch_get_state(scan_state))
+ {
+ case IFSTATE_IGNORED:
+ /* inactive branch, do nothing */
+ break;
+ case IFSTATE_TRUE:
+ /* just finished true section of active branch
*/
+ psqlscan_branch_set_state(scan_state,
IFSTATE_IGNORED);
+ break;
+ case IFSTATE_FALSE:
+ /* determine if this section is true or not */
+ if (read_boolean_expression(scan_state,
"\\elseif"))
+ psqlscan_branch_set_state(scan_state,
IFSTATE_TRUE);
+ break;
+ case IFSTATE_ELSE_TRUE:
+ case IFSTATE_ELSE_FALSE:
+ psql_error("encountered \\elseif after
\\else\n");
+ break;
+ default:
+ break;
+ }
+ psql_scan_reset(scan_state);
+ }
+
+ else if (strcmp(cmd, "else") == 0)
+ {
+ if (psqlscan_branch_empty(scan_state))
+ psql_error("encountered un-matched \\else\n");
+
+ switch (psqlscan_branch_get_state(scan_state))
+ {
+ case IFSTATE_TRUE:
+ /* just finished true section of active branch
*/
+ case IFSTATE_IGNORED:
+ /* whole branch was inactive */
+ psqlscan_branch_set_state(scan_state,
IFSTATE_ELSE_FALSE);
+ break;
+ case IFSTATE_FALSE:
+ /* just finished true section of active branch
*/
+ psqlscan_branch_set_state(scan_state,
IFSTATE_ELSE_TRUE);
+ break;
+ case IFSTATE_ELSE_TRUE:
+ case IFSTATE_ELSE_FALSE:
+ psql_error("encountered \\else after \\else\n");
+ break;
+ default:
+ break;
+ }
+ psql_scan_reset(scan_state);
+ }
+
+ else if (strcmp(cmd, "endif") == 0)
+ {
+ if (psqlscan_branch_empty(scan_state))
+ psql_error("encountered un-matched \\endif\n");
+ psqlscan_branch_end_state(scan_state);
+ psql_scan_reset(scan_state);
+ }
+
/* \l is list databases */
else if (strcmp(cmd, "l") == 0 || strcmp(cmd, "list") == 0 ||
strcmp(cmd, "l+") == 0 || strcmp(cmd, "list+") == 0)
diff --git a/src/bin/psql/mainloop.c b/src/bin/psql/mainloop.c
index bb306a4..8f12e55 100644
--- a/src/bin/psql/mainloop.c
+++ b/src/bin/psql/mainloop.c
@@ -15,7 +15,7 @@
#include "settings.h"
#include "mb/pg_wchar.h"
-
+#include "fe_utils/psqlscan_int.h"
/* callback functions for our flex lexer */
const PsqlScanCallbacks psqlscan_callbacks = {
@@ -23,7 +23,6 @@ const PsqlScanCallbacks psqlscan_callbacks = {
psql_error
};
-
/*
* Main processing loop for reading lines of input
* and sending them to the backend.
@@ -51,6 +50,9 @@ MainLoop(FILE *source)
volatile int count_eof = 0;
volatile bool die_on_error = false;
+ /* only needed at the end to detect unbalanced ifs in scan_state */
+ bool if_endifs_balanced = true;
+
/* Save the prior command source */
FILE *prev_cmd_source;
bool prev_cmd_interactive;
@@ -285,21 +287,28 @@ MainLoop(FILE *source)
if (scan_result == PSCAN_SEMICOLON ||
(scan_result == PSCAN_EOL && pset.singleline))
{
- /*
- * Save query in history. We use history_buf
to accumulate
- * multi-line queries into a single history
entry.
- */
- if (pset.cur_cmd_interactive &&
!line_saved_in_history)
+ if (psqlscan_branch_active(scan_state))
{
- pg_append_history(line, history_buf);
- pg_send_history(history_buf);
- line_saved_in_history = true;
+ /*
+ * Save query in history. We use
history_buf to accumulate
+ * multi-line queries into a single
history entry.
+ */
+ if (pset.cur_cmd_interactive &&
!line_saved_in_history)
+ {
+ pg_append_history(line,
history_buf);
+ pg_send_history(history_buf);
+ line_saved_in_history = true;
+ }
+
+ /* execute query */
+ success = SendQuery(query_buf->data);
}
+ else
+ success = true;
- /* execute query */
- success = SendQuery(query_buf->data);
slashCmdStatus = success ? PSQL_CMD_SEND :
PSQL_CMD_ERROR;
pset.stmt_lineno = 1;
+ slashCmdStatus = success ? PSQL_CMD_SEND :
PSQL_CMD_ERROR;
/* transfer query to previous_buf by
pointer-swapping */
{
@@ -352,21 +361,28 @@ MainLoop(FILE *source)
if ((slashCmdStatus == PSQL_CMD_SEND ||
slashCmdStatus == PSQL_CMD_NEWEDIT) &&
query_buf->len == 0)
{
+ /* TODO check if-then-skip-state */
/* copy previous buffer to current for
handling */
appendPQExpBufferStr(query_buf,
previous_buf->data);
}
if (slashCmdStatus == PSQL_CMD_SEND)
{
- success = SendQuery(query_buf->data);
-
- /* transfer query to previous_buf by
pointer-swapping */
+ if (psqlscan_branch_active(scan_state))
{
- PQExpBuffer swap_buf =
previous_buf;
+ success =
SendQuery(query_buf->data);
- previous_buf = query_buf;
- query_buf = swap_buf;
+ /* transfer query to
previous_buf by pointer-swapping */
+ {
+ PQExpBuffer swap_buf =
previous_buf;
+
+ previous_buf =
query_buf;
+ query_buf = swap_buf;
+ }
}
+ else
+ success = true;
+
resetPQExpBuffer(query_buf);
/* flush any paren nesting info after
forced send */
@@ -425,12 +441,17 @@ MainLoop(FILE *source)
if (query_buf->len > 0 && !pset.cur_cmd_interactive &&
successResult == EXIT_SUCCESS)
{
- /* save query in history */
- if (pset.cur_cmd_interactive)
- pg_send_history(history_buf);
+ if (psqlscan_branch_active(scan_state))
+ {
+ /* save query in history */
+ if (pset.cur_cmd_interactive)
+ pg_send_history(history_buf);
- /* execute query */
- success = SendQuery(query_buf->data);
+ /* execute query */
+ success = SendQuery(query_buf->data);
+ }
+ else
+ success = true;
if (!success && die_on_error)
successResult = EXIT_USER;
@@ -451,11 +472,17 @@ MainLoop(FILE *source)
destroyPQExpBuffer(previous_buf);
destroyPQExpBuffer(history_buf);
+ if (slashCmdStatus != PSQL_CMD_TERMINATE)
+ if_endifs_balanced = psqlscan_branch_empty(scan_state);
+
psql_scan_destroy(scan_state);
pset.cur_cmd_source = prev_cmd_source;
pset.cur_cmd_interactive = prev_cmd_interactive;
pset.lineno = prev_lineno;
+ if (! if_endifs_balanced )
+ psql_error("found EOF before closing \\endif(s)\n");
+
return successResult;
} /* MainLoop() */
diff --git a/src/bin/psql/mainloop.h b/src/bin/psql/mainloop.h
index 228a5e0..47f4c32 100644
--- a/src/bin/psql/mainloop.h
+++ b/src/bin/psql/mainloop.h
@@ -14,4 +14,5 @@ extern const PsqlScanCallbacks psqlscan_callbacks;
extern int MainLoop(FILE *source);
+
#endif /* MAINLOOP_H */
diff --git a/src/fe_utils/psqlscan.l b/src/fe_utils/psqlscan.l
index 1b29341..881c4f8 100644
--- a/src/fe_utils/psqlscan.l
+++ b/src/fe_utils/psqlscan.l
@@ -904,6 +904,9 @@ psql_scan_create(const PsqlScanCallbacks *callbacks)
psql_scan_reset(state);
+ state->branch_stack = NULL;
+ state->branch_block_active = true;
+
return state;
}
@@ -919,6 +922,13 @@ psql_scan_destroy(PsqlScanState state)
yylex_destroy(state->scanner);
+ while (state->branch_stack != NULL)
+ {
+ IfStackElem *p = state->branch_stack;
+ state->branch_stack = state->branch_stack->next;
+ free(p);
+ }
+
free(state);
}
@@ -1426,3 +1436,103 @@ psqlscan_escape_variable(PsqlScanState state, const
char *txt, int len,
psqlscan_emit(state, txt, len);
}
}
+
+/*
+ * psqlscan_branch_empty
+ *
+ * True if there are no active \if-structures
+ */
+bool
+psqlscan_branch_empty(PsqlScanState state)
+{
+ return (state->branch_stack == NULL);
+}
+
+/*
+ * psqlscan_branch_active
+ *
+ * True if the current \if-block (if any) is true and queries/commands
+ * should be executed.
+ */
+bool
+psqlscan_branch_active(PsqlScanState state)
+{
+ return state->branch_block_active;
+}
+
+/*
+ * Fetch the current state of the top of the stack
+ */
+ifState
+psqlscan_branch_get_state(PsqlScanState state)
+{
+ if (psqlscan_branch_empty(state))
+ return IFSTATE_NONE;
+ return state->branch_stack->if_state;
+}
+
+/*
+ * psqlscan_branch_update_active
+ *
+ * Scan the branch_stack to determine whether the next statements
+ * can execute or should be skipped. Cache this result in
+ * branch_block_active.
+ */
+static void
+psqlscan_branch_update_active(PsqlScanState state)
+{
+ ifState s = psqlscan_branch_get_state(state);
+ state->branch_block_active = ( (s == IFSTATE_NONE) ||
+ (s ==
IFSTATE_TRUE) ||
+ (s ==
IFSTATE_ELSE_TRUE));
+}
+
+/*
+ * psqlscan_branch_push
+ *
+ * Create a new \if branch.
+ */
+bool
+psqlscan_branch_push(PsqlScanState state, ifState new_state)
+{
+ IfStackElem *p = pg_malloc0(sizeof(IfStackElem));
+ p->if_state = new_state;
+ p->next = state->branch_stack;
+ state->branch_stack = p;
+ psqlscan_branch_update_active(state);
+ return true;
+}
+
+/*
+ * psqlscan_branch_set_state
+ *
+ * Change the state of the topmost branch.
+ * Returns false if there was branch state to set.
+ */
+bool
+psqlscan_branch_set_state(PsqlScanState state, ifState new_state)
+{
+ if (psqlscan_branch_empty(state))
+ return false;
+ state->branch_stack->if_state = new_state;
+ psqlscan_branch_update_active(state);
+ return true;
+}
+
+/*
+ * psqlscan_branch_end_state
+ *
+ * Destroy the topmost branch because and \endif was encountered.
+ * Returns false if there was no branch to end.
+ */
+bool
+psqlscan_branch_end_state(PsqlScanState state)
+{
+ IfStackElem *p = state->branch_stack;
+ if (!p)
+ return false;
+ state->branch_stack = state->branch_stack->next;
+ free(p);
+ psqlscan_branch_update_active(state);
+ return true;
+}
diff --git a/src/include/fe_utils/psqlscan_int.h
b/src/include/fe_utils/psqlscan_int.h
index 0fddc7a..e9773ca 100644
--- a/src/include/fe_utils/psqlscan_int.h
+++ b/src/include/fe_utils/psqlscan_int.h
@@ -75,6 +75,30 @@ typedef struct StackElem
struct StackElem *next;
} StackElem;
+typedef enum _ifState
+{
+ IFSTATE_NONE = 0, /* Not currently in an \if block */
+ IFSTATE_TRUE, /* currently in an \if or \elseif which is true
+ * and all parent branches (if
any) are true */
+ IFSTATE_FALSE, /* currently in an \if or \elseif which is false
+ * but no true branch has yet
been seen,
+ * and all parent branches (if
any) are true */
+ IFSTATE_IGNORED, /* currently in an \elseif which follows a true
\if
+ * or the whole \if is a child
of a false parent */
+ IFSTATE_ELSE_TRUE, /* currently in an \else which is true
+ * and all parent branches (if
any) are true */
+ IFSTATE_ELSE_FALSE /* currently in an \else which is false or
ignored */
+} ifState;
+
+/*
+ * The state of nested ifs is stored in a stack.
+ */
+typedef struct IfStackElem
+{
+ ifState if_state;
+ struct IfStackElem *next;
+} IfStackElem;
+
/*
* All working state of the lexer must be stored in PsqlScanStateData
* between calls. This allows us to have multiple open lexer operations,
@@ -118,6 +142,12 @@ typedef struct PsqlScanStateData
* Callback functions provided by the program making use of the lexer.
*/
const PsqlScanCallbacks *callbacks;
+
+ /*
+ * \if branch state variables
+ */
+ IfStackElem *branch_stack;
+ bool branch_block_active;
} PsqlScanStateData;
@@ -141,4 +171,21 @@ extern void psqlscan_escape_variable(PsqlScanState state,
const char *txt, int len,
bool as_ident);
+/*
+ * branching commands
+ */
+extern bool psqlscan_branch_empty(PsqlScanState state);
+
+extern bool psqlscan_branch_active(PsqlScanState state);
+
+extern ifState psqlscan_branch_get_state(PsqlScanState state);
+
+extern bool psqlscan_branch_push(PsqlScanState state,
+ ifState
new_state);
+
+extern bool psqlscan_branch_set_state(PsqlScanState state,
+ ifState
new_state);
+
+extern bool psqlscan_branch_end_state(PsqlScanState state);
+
#endif /* PSQLSCAN_INT_H */
diff --git a/src/test/regress/expected/psql.out
b/src/test/regress/expected/psql.out
index 464436a..7492a92 100644
--- a/src/test/regress/expected/psql.out
+++ b/src/test/regress/expected/psql.out
@@ -2686,6 +2686,33 @@ deallocate q;
\pset format aligned
\pset expanded off
\pset border 1
+\if true
+ \if 1
+ \if yes
+ \if on
+ \echo 'all true'
+all true
+ \endif
+ \endif
+ \endif
+\endif
+\if false
+\elseif 0
+\elseif no
+\elseif off
+\else
+ \echo 'all false'
+all false
+\endif
+\if true
+\else
+ \echo 'should not print #1'
+\endif
+\if false
+\elseif true
+\else
+ \echo 'should not print #2'
+\endif
-- SHOW_CONTEXT
\set SHOW_CONTEXT never
do $$
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index 900aa7e..ef1be30 100644
--- a/src/test/regress/sql/psql.sql
+++ b/src/test/regress/sql/psql.sql
@@ -357,6 +357,36 @@ deallocate q;
\pset expanded off
\pset border 1
+\if true
+ \if 1
+ \if yes
+ \if on
+ \echo 'all true'
+ \endif
+ \endif
+ \endif
+\endif
+
+\if false
+\elseif 0
+\elseif no
+\elseif off
+\else
+ \echo 'all false'
+\endif
+
+\if true
+\else
+ \echo 'should not print #1'
+\endif
+
+\if false
+\elseif true
+\else
+ \echo 'should not print #2'
+\endif
+
+
-- SHOW_CONTEXT
\set SHOW_CONTEXT never
--
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