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Add a \gexec command to psql for evaluation of computed queries. 

\gexec executes the just-entered query, like \g, but instead of printing
the results it takes each field as a SQL command to send to the server.
Computing a series of queries to be executed is a fairly common thing,
but up to now you always had to resort to kluges like writing the queries
to a file and then inputting the file.  Now it can be done with no
intermediate step.

The implementation is fairly straightforward except for its interaction
with FETCH_COUNT.  ExecQueryUsingCursor isn't capable of being called
recursively, and even if it were, its need to create a transaction
block interferes unpleasantly with the desired behavior of \gexec after
a failure of a generated query (i.e., that it can continue).  Therefore,
disable use of ExecQueryUsingCursor when doing the master \gexec query.
We can still apply it to individual generated queries, however, and there
might be some value in doing so.

While testing this feature's interaction with single-step mode, I (tgl) was
led to conclude that SendQuery needs to recognize SIGINT (cancel_pressed)
as a negative response to the single-step prompt.  Perhaps that's a
back-patchable bug fix, but for now I just included it here.

Corey Huinker, reviewed by Jim Nasby, Daniel Vérité, and myself
This commit is contained in:
Tom Lane 2016-04-04 15:25:16 -04:00
parent 66229ac004
commit 2bbe9112ae
8 changed files with 207 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
doc/src/sgml/ref/psql-ref.sgml
View File

@ -1766,6 +1766,49 @@ Tue Oct 26 21:40:57 CEST 1999
</listitem>
</varlistentry>
<varlistentry>
<term><literal>\gexec</literal></term>
<listitem>
<para>
Sends the current query input buffer to the server, then treats
each column of each row of the query's output (if any) as a SQL
statement to be executed. For example, to create an index on each
column of <structname>my_table</>:
<programlisting>
=&gt; <userinput>SELECT format('create index on my_table(%I)', attname)</>
-&gt; <userinput>FROM pg_attribute</>
-&gt; <userinput>WHERE attrelid = 'my_table'::regclass AND attnum &gt; 0</>
-&gt; <userinput>ORDER BY attnum</>
-&gt; <userinput>\gexec</>
CREATE INDEX
CREATE INDEX
CREATE INDEX
CREATE INDEX
</programlisting>
</para>
<para>
The generated queries are executed in the order in which the rows
are returned, and left-to-right within each row if there is more
than one column. NULL fields are ignored. The generated queries
are sent literally to the server for processing, so they cannot be
<application>psql</> meta-commands nor contain <application>psql</>
variable references. If any individual query fails, execution of
the remaining queries continues
unless <varname>ON_ERROR_STOP</varname> is set. Execution of each
query is subject to <varname>ECHO</varname> processing.
(Setting <varname>ECHO</varname> to <literal>all</literal>
or <literal>queries</literal> is often advisable when
using <command>\gexec</>.) Query logging, single-step mode,
timing, and other query execution features apply to each generated
query as well.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>\gset [ <replaceable class="parameter">prefix</replaceable> ]</literal></term>

7
src/bin/psql/command.c
View File

@ -871,6 +871,13 @@ exec_command(const char *cmd,
status = PSQL_CMD_SEND;
}
/* \gexec -- send query and execute each field of result */
else if (strcmp(cmd, "gexec") == 0)
{
pset.gexec_flag = true;
status = PSQL_CMD_SEND;
}
/* \gset [prefix] -- send query and store result into variables */
else if (strcmp(cmd, "gset") == 0)
{

90
src/bin/psql/common.c
View File

@ -797,6 +797,76 @@ StoreQueryTuple(const PGresult *result)
}
/*
* ExecQueryTuples: assuming query result is OK, execute each query
* result field as a SQL statement
*
* Returns true if successful, false otherwise.
*/
static bool
ExecQueryTuples(const PGresult *result)
{
bool success = true;
int nrows = PQntuples(result);
int ncolumns = PQnfields(result);
int r,
c;
/*
* We must turn off gexec_flag to avoid infinite recursion. Note that
* this allows ExecQueryUsingCursor to be applied to the individual query
* results. SendQuery prevents it from being applied when fetching the
* queries-to-execute, because it can't handle recursion either.
*/
pset.gexec_flag = false;
for (r = 0; r < nrows; r++)
{
for (c = 0; c < ncolumns; c++)
{
if (!PQgetisnull(result, r, c))
{
const char *query = PQgetvalue(result, r, c);
/* Abandon execution if cancel_pressed */
if (cancel_pressed)
goto loop_exit;
/*
* ECHO_ALL mode should echo these queries, but SendQuery
* assumes that MainLoop did that, so we have to do it here.
*/
if (pset.echo == PSQL_ECHO_ALL && !pset.singlestep)
{
puts(query);
fflush(stdout);
}
if (!SendQuery(query))
{
/* Error - abandon execution if ON_ERROR_STOP */
success = false;
if (pset.on_error_stop)
goto loop_exit;
}
}
}
}
loop_exit:
/*
* Restore state. We know gexec_flag was on, else we'd not be here. (We
* also know it'll get turned off at end of command, but that's not ours
* to do here.)
*/
pset.gexec_flag = true;
/* Return true if all queries were successful */
return success;
}
/*
* ProcessResult: utility function for use by SendQuery() only
*
@ -971,7 +1041,7 @@ PrintQueryStatus(PGresult *results)
/*
* PrintQueryResults: print out (or store) query results as required
* PrintQueryResults: print out (or store or execute) query results as required
*
* Note: Utility function for use by SendQuery() only.
*
@ -989,9 +1059,11 @@ PrintQueryResults(PGresult *results)
switch (PQresultStatus(results))
{
case PGRES_TUPLES_OK:
/* store or print the data ... */
/* store or execute or print the data ... */
if (pset.gset_prefix)
success = StoreQueryTuple(results);
else if (pset.gexec_flag)
success = ExecQueryTuples(results);
else
success = PrintQueryTuples(results);
/* if it's INSERT/UPDATE/DELETE RETURNING, also print status */
@ -1068,6 +1140,7 @@ SendQuery(const char *query)
{
char buf[3];
fflush(stderr);
printf(_("***(Single step mode: verify command)*******************************************\n"
"%s\n"
"***(press return to proceed or enter x and return to cancel)********************\n"),
@ -1076,6 +1149,8 @@ SendQuery(const char *query)
if (fgets(buf, sizeof(buf), stdin) != NULL)
if (buf[0] == 'x')
goto sendquery_cleanup;
if (cancel_pressed)
goto sendquery_cleanup;
}
else if (pset.echo == PSQL_ECHO_QUERIES)
{
@ -1138,7 +1213,7 @@ SendQuery(const char *query)
}
}
if (pset.fetch_count <= 0 || !is_select_command(query))
if (pset.fetch_count <= 0 || pset.gexec_flag || !is_select_command(query))
{
/* Default fetch-it-all-and-print mode */
instr_time before,
@ -1278,6 +1353,9 @@ sendquery_cleanup:
pset.gset_prefix = NULL;
}
/* reset \gexec trigger */
pset.gexec_flag = false;
return OK;
}
@ -1423,6 +1501,8 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
break;
}
/* Note we do not deal with \gexec mode here */
ntuples = PQntuples(results);
if (ntuples < fetch_count)
@ -1499,8 +1579,10 @@ cleanup:
{
OK = AcceptResult(results) &&
(PQresultStatus(results) == PGRES_COMMAND_OK);
ClearOrSaveResult(results);
}
ClearOrSaveResult(results);
else
PQclear(results);
if (started_txn)
{

3
src/bin/psql/help.c
View File

@ -168,12 +168,13 @@ slashUsage(unsigned short int pager)
* Use "psql --help=commands | wc" to count correctly. It's okay to count
* the USE_READLINE line even in builds without that.
*/
output = PageOutput(110, pager ? &(pset.popt.topt) : NULL);
output = PageOutput(111, pager ? &(pset.popt.topt) : NULL);
fprintf(output, _("General\n"));
fprintf(output, _(" \\copyright show PostgreSQL usage and distribution terms\n"));
fprintf(output, _(" \\errverbose show most recent error message at maximum verbosity\n"));
fprintf(output, _(" \\g [FILE] or ; execute query (and send results to file or |pipe)\n"));
fprintf(output, _(" \\gexec execute query, then execute each value in its result\n"));
fprintf(output, _(" \\gset [PREFIX] execute query and store results in psql variables\n"));
fprintf(output, _(" \\q quit psql\n"));
fprintf(output, _(" \\watch [SEC] execute query every SEC seconds\n"));

1
src/bin/psql/settings.h
View File

@ -92,6 +92,7 @@ typedef struct _psqlSettings
char *gfname; /* one-shot file output argument for \g */
char *gset_prefix; /* one-shot prefix argument for \gset */
bool gexec_flag; /* one-shot flag to execute query's results */
bool notty; /* stdin or stdout is not a tty (as determined
* on startup) */

2
src/bin/psql/tab-complete.c
View File

@ -1281,7 +1281,7 @@ psql_completion(const char *text, int start, int end)
"\\dm", "\\dn", "\\do", "\\dO", "\\dp", "\\drds", "\\ds", "\\dS",
"\\dt", "\\dT", "\\dv", "\\du", "\\dx", "\\dy",
"\\e", "\\echo", "\\ef", "\\encoding", "\\errverbose", "\\ev",
"\\f", "\\g", "\\gset", "\\h", "\\help", "\\H", "\\i", "\\ir", "\\l",
"\\f", "\\g", "\\gexec", "\\gset", "\\h", "\\help", "\\H", "\\i", "\\ir", "\\l",
"\\lo_import", "\\lo_export", "\\lo_list", "\\lo_unlink",
"\\o", "\\p", "\\password", "\\prompt", "\\pset", "\\q", "\\qecho", "\\r",
"\\s", "\\set", "\\setenv", "\\sf", "\\sv", "\\t", "\\T",

45
src/test/regress/expected/psql.out
View File

@ -51,6 +51,51 @@ select 10 as test01, 20 as test02 from generate_series(1,3) \gset
more than one row returned for \gset
select 10 as test01, 20 as test02 from generate_series(1,0) \gset
no rows returned for \gset
\unset FETCH_COUNT
-- \gexec
create temporary table gexec_test(a int, b text, c date, d float);
select format('create index on gexec_test(%I)', attname)
from pg_attribute
where attrelid = 'gexec_test'::regclass and attnum > 0
order by attnum
\gexec
create index on gexec_test(a)
create index on gexec_test(b)
create index on gexec_test(c)
create index on gexec_test(d)
-- \gexec should work in FETCH_COUNT mode too
-- (though the fetch limit applies to the executed queries not the meta query)
\set FETCH_COUNT 1
select 'select 1 as ones', 'select x.y, x.y*2 as double from generate_series(1,4) as x(y)'
union all
select 'drop table gexec_test', NULL
union all
select 'drop table gexec_test', 'select ''2000-01-01''::date as party_over'
\gexec
select 1 as ones
ones
------
1
(1 row)
select x.y, x.y*2 as double from generate_series(1,4) as x(y)
y | double
---+--------
1 | 2
2 | 4
3 | 6
4 | 8
(4 rows)
drop table gexec_test
drop table gexec_test
ERROR: table "gexec_test" does not exist
select '2000-01-01'::date as party_over
party_over
------------
01-01-2000
(1 row)
\unset FETCH_COUNT
-- show all pset options
\pset

22
src/test/regress/sql/psql.sql
View File

@ -38,6 +38,28 @@ select 10 as test01, 20 as test02 from generate_series(1,0) \gset
\unset FETCH_COUNT
-- \gexec
create temporary table gexec_test(a int, b text, c date, d float);
select format('create index on gexec_test(%I)', attname)
from pg_attribute
where attrelid = 'gexec_test'::regclass and attnum > 0
order by attnum
\gexec
-- \gexec should work in FETCH_COUNT mode too
-- (though the fetch limit applies to the executed queries not the meta query)
\set FETCH_COUNT 1
select 'select 1 as ones', 'select x.y, x.y*2 as double from generate_series(1,4) as x(y)'
union all
select 'drop table gexec_test', NULL
union all
select 'drop table gexec_test', 'select ''2000-01-01''::date as party_over'
\gexec
\unset FETCH_COUNT
-- show all pset options
\pset