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psql: Add command to use extended query protocol
This adds a new psql command \bind that sets query parameters and causes the next query to be sent using the extended query protocol. Example: SELECT $1, $2 \bind 'foo' 'bar' \g This may be useful for psql scripting, but one of the main purposes is also to be able to test various aspects of the extended query protocol from psql and to write tests more easily. Reviewed-by: Corey Huinker <[email protected]> Discussion: https://www.postgresql.org/message-id/flat/[email protected]
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‎doc/src/sgml/ref/psql-ref.sgml‎

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@@ -879,6 +879,42 @@ testdb=&gt;
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>\bind</literal> [ <replaceable class="parameter">parameter</replaceable> ] ... </term>
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<listitem>
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<para>
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Sets query parameters for the next query execution, with the
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specified parameters passed for any parameter placeholders
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(<literal>$1</literal> etc.).
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</para>
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<para>
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Example:
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<programlisting>
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INSERT INTO tbl1 VALUES ($1, $2) \bind 'first value' 'second value' \g
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</programlisting>
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</para>
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<para>
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This also works for query-execution commands besides
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<literal>\g</literal>, such as <literal>\gx</literal> and
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<literal>\gset</literal>.
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</para>
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<para>
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This command causes the extended query protocol (see <xref
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linkend="protocol-query-concepts"/>) to be used, unlike normal
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<application>psql</application> operation, which uses the simple
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query protocol. So this command can be useful to test the extended
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query protocol from psql. (The extended query protocol is used even
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if the query has no parameters and this command specifies zero
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parameters.) This command affects only the next query executed; all
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subsequent queries will use the simple query protocol by default.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>\c</literal> or <literal>\connect [ -reuse-previous=<replaceable class="parameter">on|off</replaceable> ] [ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">username</replaceable> ] [ <replaceable class="parameter">host</replaceable> ] [ <replaceable class="parameter">port</replaceable> ] | <replaceable class="parameter">conninfo</replaceable> ]</literal></term>
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<listitem>

‎src/bin/psql/command.c‎

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@@ -63,6 +63,7 @@ static backslashResult exec_command(const char *cmd,
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PQExpBuffer query_buf,
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PQExpBuffer previous_buf);
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static backslashResult exec_command_a(PsqlScanState scan_state, bool active_branch);
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static backslashResult exec_command_bind(PsqlScanState scan_state, bool active_branch);
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static backslashResult exec_command_C(PsqlScanState scan_state, bool active_branch);
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static backslashResult exec_command_connect(PsqlScanState scan_state, bool active_branch);
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static backslashResult exec_command_cd(PsqlScanState scan_state, bool active_branch,
@@ -308,6 +309,8 @@ exec_command(const char *cmd,
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if (strcmp(cmd, "a") == 0)
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status = exec_command_a(scan_state, active_branch);
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else if (strcmp(cmd, "bind") == 0)
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status = exec_command_bind(scan_state, active_branch);
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else if (strcmp(cmd, "C") == 0)
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status = exec_command_C(scan_state, active_branch);
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else if (strcmp(cmd, "c") == 0 || strcmp(cmd, "connect") == 0)
@@ -453,6 +456,40 @@ exec_command_a(PsqlScanState scan_state, bool active_branch)
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return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
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}
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/*
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* \bind -- set query parameters
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*/
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static backslashResult
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exec_command_bind(PsqlScanState scan_state, bool active_branch)
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{
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backslashResult status = PSQL_CMD_SKIP_LINE;
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if (active_branch)
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{
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char *opt;
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int nparams = 0;
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int nalloc = 0;
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pset.bind_params = NULL;
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while ((opt = psql_scan_slash_option(scan_state, OT_NORMAL, NULL, false)))
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{
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nparams++;
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if (nparams > nalloc)
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{
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nalloc = nalloc ? nalloc * 2 : 1;
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pset.bind_params = pg_realloc_array(pset.bind_params, char *, nalloc);
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}
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pset.bind_params[nparams - 1] = pg_strdup(opt);
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}
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pset.bind_nparams = nparams;
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pset.bind_flag = true;
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}
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return status;
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}
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/*
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* \C -- override table title (formerly change HTML caption)
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*/

‎src/bin/psql/common.c‎

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@@ -1220,6 +1220,16 @@ SendQuery(const char *query)
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pset.gsavepopt = NULL;
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}
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/* clean up after \bind */
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if (pset.bind_flag)
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{
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for (i = 0; i < pset.bind_nparams; i++)
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free(pset.bind_params[i]);
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free(pset.bind_params);
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pset.bind_params = NULL;
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pset.bind_flag = false;
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}
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/* reset \gset trigger */
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if (pset.gset_prefix)
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{
@@ -1397,7 +1407,10 @@ ExecQueryAndProcessResults(const char *query,
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if (timing)
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INSTR_TIME_SET_CURRENT(before);
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success = PQsendQuery(pset.db, query);
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if (pset.bind_flag)
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success = PQsendQueryParams(pset.db, query, pset.bind_nparams, NULL, (const char * const *) pset.bind_params, NULL, NULL, 0);
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else
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success = PQsendQuery(pset.db, query);
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if (!success)
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{

‎src/bin/psql/help.c‎

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@@ -189,6 +189,7 @@ slashUsage(unsigned short int pager)
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initPQExpBuffer(&buf);
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HELP0("General\n");
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HELP0(" \\bind [PARAM]... set query parameters\n");
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HELP0(" \\copyright show PostgreSQL usage and distribution terms\n");
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HELP0(" \\crosstabview [COLUMNS] execute query and display result in crosstab\n");
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HELP0(" \\errverbose show most recent error message at maximum verbosity\n");

‎src/bin/psql/settings.h‎

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@@ -96,6 +96,9 @@ typedef struct _psqlSettings
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char *gset_prefix; /* one-shot prefix argument for \gset */
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bool gdesc_flag; /* one-shot request to describe query result */
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bool gexec_flag; /* one-shot request to execute query result */
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bool bind_flag; /* one-shot request to use extended query protocol */
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int bind_nparams; /* number of parameters */
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char **bind_params; /* parameters for extended query protocol call */
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bool crosstab_flag; /* one-shot request to crosstab result */
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char *ctv_args[4]; /* \crosstabview arguments */
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‎src/bin/psql/tab-complete.c‎

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@@ -1680,6 +1680,7 @@ psql_completion(const char *text, int start, int end)
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/* psql's backslash commands. */
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static const char *const backslash_commands[] = {
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"\\a",
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"\\bind",
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"\\connect", "\\conninfo", "\\C", "\\cd", "\\copy",
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"\\copyright", "\\crosstabview",
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"\\d", "\\da", "\\dA", "\\dAc", "\\dAf", "\\dAo", "\\dAp",

‎src/test/regress/expected/psql.out‎

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@@ -98,6 +98,37 @@ two | 2
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1 | 2
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(1 row)
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-- \bind (extended query protocol)
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SELECT 1 \bind \g
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?column?
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----------
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1
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(1 row)
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SELECT $1 \bind 'foo' \g
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?column?
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----------
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foo
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(1 row)
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SELECT $1, $2 \bind 'foo' 'bar' \g
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?column? | ?column?
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----------+----------
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foo | bar
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(1 row)
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-- errors
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-- parse error
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SELECT foo \bind \g
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ERROR: column "foo" does not exist
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LINE 1: SELECT foo
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^
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-- tcop error
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SELECT 1 \; SELECT 2 \bind \g
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ERROR: cannot insert multiple commands into a prepared statement
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-- bind error
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SELECT $1, $2 \bind 'foo' \g
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ERROR: bind message supplies 1 parameters, but prepared statement "" requires 2
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-- \gset
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select 10 as test01, 20 as test02, 'Hello' as test03 \gset pref01_
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\echo :pref01_test01 :pref01_test02 :pref01_test03

‎src/test/regress/sql/psql.sql‎

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@@ -45,6 +45,20 @@ SELECT 1 as one, 2 as two \g (format=csv csv_fieldsep='\t')
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SELECT 1 as one, 2 as two \gx (title='foo bar')
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\g
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-- \bind (extended query protocol)
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SELECT 1 \bind \g
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SELECT $1 \bind 'foo' \g
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SELECT $1, $2 \bind 'foo' 'bar' \g
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-- errors
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-- parse error
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SELECT foo \bind \g
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-- tcop error
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SELECT 1 \; SELECT 2 \bind \g
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-- bind error
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SELECT $1, $2 \bind 'foo' \g
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-- \gset
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select 10 as test01, 20 as test02, 'Hello' as test03 \gset pref01_

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