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builtins: implement pg_get_function_arg_default
Release note (sql change): The pg_get_function_arg_default builtin function has been implemented. This also causes the information_schema.parameters(parameter_default) column to be populated correctly.
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‎docs/generated/sql/functions.md‎

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@@ -3615,7 +3615,7 @@ may increase either contention or retry errors, or both.</p>
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</span></td><td>Stable</td></tr>
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<tr><td><a name="pg_function_is_visible"></a><code>pg_function_is_visible(oid: oid) &rarr; <a href="bool.html">bool</a></code></td><td><span class="funcdesc"><p>Returns whether the function with the given OID belongs to one of the schemas on the search path.</p>
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</span></td><td>Stable</td></tr>
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<tr><td><a name="pg_get_function_arg_default"></a><code>pg_get_function_arg_default(func_oid: oid, arg_num: int4) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Get textual representation of a function argument’s default value. The second argument of this function is the argument number among all arguments (i.e. proallargtypes, <em>not</em> proargtypes), starting with 1, because that’s how information_schema.sql uses it. Currently, this always returns NULL, since CockroachDB does not support default values.</p>
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<tr><td><a name="pg_get_function_arg_default"></a><code>pg_get_function_arg_default(func_oid: oid, arg_num: int4) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Get textual representation of a function argument’s default value. The second argument of this function is the argument number among all arguments (i.e. proallargtypes, <em>not</em> proargtypes), starting with 1, because that’s how information_schema.sql uses it.</p>
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</span></td><td>Stable</td></tr>
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<tr><td><a name="pg_get_function_arguments"></a><code>pg_get_function_arguments(func_oid: oid) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns the argument list (with defaults) necessary to identify a function, in the form it would need to appear in within CREATE FUNCTION.</p>
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</span></td><td>Stable</td></tr>

‎pkg/sql/logictest/testdata/logic_test/information_schema‎

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Original file line numberDiff line numberDiff line change
@@ -3530,6 +3530,97 @@ specific_catalog specific_schema specific_name ordinal_position parameter_mo
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test pg_catalog get_byte_854 1 IN NO NO NULL bytea NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL test pg_catalog bytea NULL NULL NULL NULL 1 NULL
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test pg_catalog get_byte_854 2 IN NO NO NULL bigint NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL test pg_catalog int8 NULL NULL NULL NULL 2 NULL
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# Test that default values are populated correctly.
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statement ok
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CREATE OR REPLACE FUNCTION f_default(
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p_no_default INT,
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p_int INT DEFAULT 0,
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p_string STRING DEFAULT '0'
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)
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RETURNS varchar
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LANGUAGE plpgsql
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AS
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$$
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BEGIN
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RETURN p_no_default::varchar || ':' || p_int::varchar || ':' || p_string;
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END;
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$$
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query TT
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SELECT p.parameter_name, p.parameter_default
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FROM information_schema.routines AS r
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JOIN information_schema.parameters AS p ON r.specific_name = p.specific_name
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WHERE r.routine_name = 'f_default'
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ORDER BY p.ordinal_position;
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----
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p_no_default NULL
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p_int 0:::INT8
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p_string '0':::STRING
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# Test INOUT parameters with defaults.
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statement ok
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CREATE FUNCTION f_inout_default(
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INOUT p_inout_no_default INT,
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INOUT p_inout_with_default INT DEFAULT 42
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) RETURNS RECORD AS $$ SELECT p_inout_no_default + 1, p_inout_with_default + 1; $$ LANGUAGE SQL;
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query TT
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SELECT p.parameter_name, p.parameter_default
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FROM information_schema.routines AS r
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JOIN information_schema.parameters AS p ON r.specific_name = p.specific_name
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WHERE r.routine_name = 'f_inout_default'
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ORDER BY p.ordinal_position;
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----
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p_inout_no_default NULL
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p_inout_with_default 42:::INT8
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# Test mixed parameter modes with defaults. Note that parameters with
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# defaults must appear after all parameters without defaults.
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statement ok
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CREATE FUNCTION f_mixed_defaults(
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p_in_no_default INT,
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OUT p_out_param INT,
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INOUT p_inout_no_default INT,
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p_in_default INT DEFAULT 10,
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INOUT p_inout_default INT DEFAULT 20
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) RETURNS RECORD AS $$
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SELECT p_in_no_default + p_in_default, p_inout_no_default + 1, p_inout_default + 1;
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$$ LANGUAGE SQL;
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query TT
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SELECT p.parameter_name, p.parameter_default
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FROM information_schema.routines AS r
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JOIN information_schema.parameters AS p ON r.specific_name = p.specific_name
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WHERE r.routine_name = 'f_mixed_defaults'
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ORDER BY p.ordinal_position;
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----
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p_in_no_default NULL
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p_out_param NULL
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p_inout_no_default NULL
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p_in_default 10:::INT8
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p_inout_default 20:::INT8
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# Test complex default expressions with different parameter modes.
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statement ok
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CREATE FUNCTION f_complex_defaults(
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OUT p_out_result INT,
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INOUT p_complex_default INT DEFAULT length('test'),
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p_function_default INT DEFAULT length('hello')
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) RETURNS RECORD AS $$
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SELECT p_complex_default + p_function_default, p_complex_default;
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$$ LANGUAGE SQL;
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query TT
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SELECT p.parameter_name, p.parameter_default
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FROM information_schema.routines AS r
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JOIN information_schema.parameters AS p ON r.specific_name = p.specific_name
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WHERE r.routine_name = 'f_complex_defaults'
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ORDER BY p.ordinal_position;
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----
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p_out_result NULL
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p_complex_default length('test':::STRING)
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p_function_default length('hello':::STRING)
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skipif config local-mixed-25.2
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query TTTTTTTT colnames,rowsort
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SELECT * FROM system.information_schema.column_privileges WHERE table_name = 'eventlog'

‎pkg/sql/sem/builtins/pg_builtins.go‎

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Original file line numberDiff line numberDiff line change
@@ -773,12 +773,45 @@ var pgBuiltins = map[string]builtinDefinition{
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tree.Overload{
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Types: tree.ParamTypes{{Name: "func_oid", Typ: types.Oid}, {Name: "arg_num", Typ: types.Int4}},
775775
ReturnType: tree.FixedReturnType(types.String),
776-
Body: "SELECT NULL",
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Body: `
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WITH defaults_parsed AS (
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SELECT
779+
proargdefaults,
780+
pronargs,
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proargmodes,
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array_upper(proargmodes, 1) AS total_args,
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CASE
784+
WHEN proargdefaults IS NULL THEN 0
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ELSE array_length(string_to_array(trim('()' FROM proargdefaults), '}, {'), 1)
786+
END AS num_defaults,
787+
trim('()' FROM proargdefaults) AS defaults_trimmed,
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-- Count input arguments up to position $2
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CASE
790+
WHEN proargmodes IS NULL THEN $2
791+
ELSE (
792+
SELECT count(*)
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FROM generate_series(1, $2) AS i
794+
WHERE proargmodes[i] IN ('i', 'b', 'v')
795+
)
796+
END AS nth_input_arg
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FROM pg_catalog.pg_proc
798+
WHERE oid = $1
799+
LIMIT 1
800+
)
801+
SELECT
802+
CASE
803+
WHEN proargdefaults IS NULL THEN NULL
804+
WHEN $2 < 1 OR $2 > COALESCE(total_args, pronargs) THEN NULL
805+
WHEN (proargmodes IS NOT NULL AND proargmodes[$2] NOT IN ('i', 'b', 'v')) THEN NULL
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WHEN nth_input_arg <= (pronargs - num_defaults) THEN NULL
807+
ELSE trim('{}' FROM split_part(defaults_trimmed, '}, {', nth_input_arg - (pronargs - num_defaults)))
808+
END
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FROM defaults_parsed
810+
`,
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Info: "Get textual representation of a function argument's default value. " +
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"The second argument of this function is the argument number among all " +
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"arguments (i.e. proallargtypes, *not* proargtypes), starting with 1, " +
780-
"because that's how information_schema.sql uses it. Currently, this " +
781-
"always returns NULL, since CockroachDB does not support default values.",
814+
"because that's how information_schema.sql uses it.",
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Volatility: volatility.Stable,
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CalledOnNullInput: true,
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Language: tree.RoutineLangSQL,

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