Use attnum to identify index columns in pg_restore_attribute_stats().

Previously we used attname for both table and index columns, but
that is problematic for indexes because their attnames are assigned
by internal rules that don't guarantee to preserve the names across
dump and reload.  (This is what's causing the remaining buildfarm
failures in cross-version-upgrade tests.)  Fortunately we can use
attnum instead, since there's no such thing as adding or dropping
columns in an existing index.  We met this same problem previously
with ALTER INDEX ... SET STATISTICS, and solved it the same way,
cf commit 5b6d13e.

In pg_restore_attribute_stats() itself, we accept either attnum or
attname, but the policy used by pg_dump is to always use attname
for tables and attnum for indexes.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Author: Corey Huinker <corey.huinker@gmail.com>
Discussion: https://postgr.es/m/1457469.1740419458@sss.pgh.pa.us

Author: tglsfdc

doc/src/sgml/func.sgml

@@ -30209,8 +30209,8 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
 </programlisting>
         </para>
         <para>
-         For example, to set the <structname>relpages</structname> and
-         <structname>reltuples</structname> of the table
+         For example, to set the <structfield>relpages</structfield> and
+         <structfield>reltuples</structfield> values for the table
          <structname>mytable</structname>:
 <programlisting>
  SELECT pg_restore_relation_stats(
@@ -30222,8 +30222,8 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
         <para>
          The argument <literal>relation</literal> with a value of type
          <type>regclass</type> is required, and specifies the table. Other
-         arguments are the names of statistics corresponding to certain
-         columns in <link
+         arguments are the names and values of statistics corresponding to
+         certain columns in <link
          linkend="catalog-pg-class"><structname>pg_class</structname></link>.
          The currently-supported relation statistics are
          <literal>relpages</literal> with a value of type
@@ -30232,16 +30232,16 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
          value of type <type>integer</type>.
         </para>
         <para>
-         Additionally, this function supports argument name
+         Additionally, this function accepts argument name
          <literal>version</literal> of type <type>integer</type>, which
-         specifies the version from which the statistics originated, improving
-         interpretation of statistics from older versions of
-         <productname>PostgreSQL</productname>.
+         specifies the server version from which the statistics originated.
+         This is anticipated to be helpful in porting statistics from older
+         versions of <productname>PostgreSQL</productname>.
         </para>
         <para>
          Minor errors are reported as a <literal>WARNING</literal> and
          ignored, and remaining statistics will still be restored. If all
-         specified statistics are successfully restored, return
+         specified statistics are successfully restored, returns
          <literal>true</literal>, otherwise <literal>false</literal>.
         </para>
         <para>
@@ -30281,7 +30281,7 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
         <returnvalue>boolean</returnvalue>
        </para>
         <para>
-         Create or update column-level statistics.  Ordinarily, these
+         Creates or updates column-level statistics.  Ordinarily, these
          statistics are collected automatically or updated as a part of <xref
          linkend="sql-vacuum"/> or <xref linkend="sql-analyze"/>, so it's not
          necessary to call this function.  However, it is useful after a
@@ -30300,9 +30300,9 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
 </programlisting>
         </para>
         <para>
-         For example, to set the <structname>avg_width</structname> and
-         <structname>null_frac</structname> for the attribute
-         <structname>col1</structname> of the table
+         For example, to set the <structfield>avg_width</structfield> and
+         <structfield>null_frac</structfield> values for the attribute
+         <structfield>col1</structfield> of the table
          <structname>mytable</structname>:
 <programlisting>
  SELECT pg_restore_attribute_stats(
@@ -30315,25 +30315,26 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
         </para>
         <para>
          The required arguments are <literal>relation</literal> with a value
-         of type <type>regclass</type>, which specifies the table;
-         <literal>attname</literal> with a value of type <type>name</type>,
+         of type <type>regclass</type>, which specifies the table; either
+         <literal>attname</literal> with a value of type <type>name</type> or
+         <literal>attnum</literal> with a value of type <type>smallint</type>,
          which specifies the column; and <literal>inherited</literal>, which
-         specifies whether the statistics includes values from child tables.
-         Other arguments are the names of statistics corresponding to columns
-         in <link
+         specifies whether the statistics include values from child tables.
+         Other arguments are the names and values of statistics corresponding
+         to columns in <link
          linkend="view-pg-stats"><structname>pg_stats</structname></link>.
         </para>
         <para>
-         Additionally, this function supports argument name
+         Additionally, this function accepts argument name
          <literal>version</literal> of type <type>integer</type>, which
-         specifies the version from which the statistics originated, improving
-         interpretation of statistics from older versions of
-         <productname>PostgreSQL</productname>.
+         specifies the server version from which the statistics originated.
+         This is anticipated to be helpful in porting statistics from older
+         versions of <productname>PostgreSQL</productname>.
         </para>
         <para>
          Minor errors are reported as a <literal>WARNING</literal> and
          ignored, and remaining statistics will still be restored. If all
-         specified statistics are successfully restored, return
+         specified statistics are successfully restored, returns
          <literal>true</literal>, otherwise <literal>false</literal>.
         </para>
         <para>

src/backend/statistics/attribute_stats.c

@@ -38,6 +38,7 @@ enum attribute_stats_argnum
 {
 	ATTRELATION_ARG = 0,
 	ATTNAME_ARG,
+	ATTNUM_ARG,
 	INHERITED_ARG,
 	NULL_FRAC_ARG,
 	AVG_WIDTH_ARG,
@@ -59,6 +60,7 @@ static struct StatsArgInfo attarginfo[] =
 {
 	[ATTRELATION_ARG] = {"relation", REGCLASSOID},
 	[ATTNAME_ARG] = {"attname", NAMEOID},
+	[ATTNUM_ARG] = {"attnum", INT2OID},
 	[INHERITED_ARG] = {"inherited", BOOLOID},
 	[NULL_FRAC_ARG] = {"null_frac", FLOAT4OID},
 	[AVG_WIDTH_ARG] = {"avg_width", INT4OID},
@@ -76,6 +78,22 @@ static struct StatsArgInfo attarginfo[] =
 	[NUM_ATTRIBUTE_STATS_ARGS] = {0}
 };
 
+enum clear_attribute_stats_argnum
+{
+	C_ATTRELATION_ARG = 0,
+	C_ATTNAME_ARG,
+	C_INHERITED_ARG,
+	C_NUM_ATTRIBUTE_STATS_ARGS
+};
+
+static struct StatsArgInfo cleararginfo[] =
+{
+	[C_ATTRELATION_ARG] = {"relation", REGCLASSOID},
+	[C_ATTNAME_ARG] = {"attname", NAMEOID},
+	[C_INHERITED_ARG] = {"inherited", BOOLOID},
+	[C_NUM_ATTRIBUTE_STATS_ARGS] = {0}
+};
+
 static bool attribute_statistics_update(FunctionCallInfo fcinfo);
 static Node *get_attr_expr(Relation rel, int attnum);
 static void get_attr_stat_type(Oid reloid, AttrNumber attnum,
@@ -116,9 +134,9 @@ static bool
 attribute_statistics_update(FunctionCallInfo fcinfo)
 {
 	Oid			reloid;
-	Name		attname;
-	bool		inherited;
+	char	   *attname;
 	AttrNumber	attnum;
+	bool		inherited;
 
 	Relation	starel;
 	HeapTuple	statup;
@@ -164,21 +182,51 @@ attribute_statistics_update(FunctionCallInfo fcinfo)
 	/* lock before looking up attribute */
 	stats_lock_check_privileges(reloid);
 
-	stats_check_required_arg(fcinfo, attarginfo, ATTNAME_ARG);
-	attname = PG_GETARG_NAME(ATTNAME_ARG);
-	attnum = get_attnum(reloid, NameStr(*attname));
+	/* user can specify either attname or attnum, but not both */
+	if (!PG_ARGISNULL(ATTNAME_ARG))
+	{
+		Name		attnamename;
+
+		if (!PG_ARGISNULL(ATTNUM_ARG))
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("cannot specify both attname and attnum")));
+		attnamename = PG_GETARG_NAME(ATTNAME_ARG);
+		attname = NameStr(*attnamename);
+		attnum = get_attnum(reloid, attname);
+		/* note that this test covers attisdropped cases too: */
+		if (attnum == InvalidAttrNumber)
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_COLUMN),
+					 errmsg("column \"%s\" of relation \"%s\" does not exist",
+							attname, get_rel_name(reloid))));
+	}
+	else if (!PG_ARGISNULL(ATTNUM_ARG))
+	{
+		attnum = PG_GETARG_INT16(ATTNUM_ARG);
+		attname = get_attname(reloid, attnum, true);
+		/* annoyingly, get_attname doesn't check attisdropped */
+		if (attname == NULL ||
+			!SearchSysCacheExistsAttName(reloid, attname))
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_COLUMN),
+					 errmsg("column %d of relation \"%s\" does not exist",
+							attnum, get_rel_name(reloid))));
+	}
+	else
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("must specify either attname or attnum")));
+		attname = NULL;			/* keep compiler quiet */
+		attnum = 0;
+	}
 
 	if (attnum < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("cannot modify statistics on system column \"%s\"",
-						NameStr(*attname))));
-
-	if (attnum == InvalidAttrNumber)
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_COLUMN),
-				 errmsg("column \"%s\" of relation \"%s\" does not exist",
-						NameStr(*attname), get_rel_name(reloid))));
+						attname)));
 
 	stats_check_required_arg(fcinfo, attarginfo, INHERITED_ARG);
 	inherited = PG_GETARG_BOOL(INHERITED_ARG);
@@ -241,7 +289,7 @@ attribute_statistics_update(FunctionCallInfo fcinfo)
 								&elemtypid, &elem_eq_opr))
 		{
 			ereport(WARNING,
-					(errmsg("unable to determine element type of attribute \"%s\"", NameStr(*attname)),
+					(errmsg("unable to determine element type of attribute \"%s\"", attname),
 					 errdetail("Cannot set STATISTIC_KIND_MCELEM or STATISTIC_KIND_DECHIST.")));
 			elemtypid = InvalidOid;
 			elem_eq_opr = InvalidOid;
@@ -257,7 +305,7 @@ attribute_statistics_update(FunctionCallInfo fcinfo)
 	{
 		ereport(WARNING,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("could not determine less-than operator for attribute \"%s\"", NameStr(*attname)),
+				 errmsg("could not determine less-than operator for attribute \"%s\"", attname),
 				 errdetail("Cannot set STATISTIC_KIND_HISTOGRAM or STATISTIC_KIND_CORRELATION.")));
 
 		do_histogram = false;
@@ -271,7 +319,7 @@ attribute_statistics_update(FunctionCallInfo fcinfo)
 	{
 		ereport(WARNING,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("attribute \"%s\" is not a range type", NameStr(*attname)),
+				 errmsg("attribute \"%s\" is not a range type", attname),
 				 errdetail("Cannot set STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM or STATISTIC_KIND_BOUNDS_HISTOGRAM.")));
 
 		do_bounds_histogram = false;
@@ -857,8 +905,8 @@ pg_clear_attribute_stats(PG_FUNCTION_ARGS)
 	AttrNumber	attnum;
 	bool		inherited;
 
-	stats_check_required_arg(fcinfo, attarginfo, ATTRELATION_ARG);
-	reloid = PG_GETARG_OID(ATTRELATION_ARG);
+	stats_check_required_arg(fcinfo, cleararginfo, C_ATTRELATION_ARG);
+	reloid = PG_GETARG_OID(C_ATTRELATION_ARG);
 
 	if (RecoveryInProgress())
 		ereport(ERROR,
@@ -868,8 +916,8 @@ pg_clear_attribute_stats(PG_FUNCTION_ARGS)
 
 	stats_lock_check_privileges(reloid);
 
-	stats_check_required_arg(fcinfo, attarginfo, ATTNAME_ARG);
-	attname = PG_GETARG_NAME(ATTNAME_ARG);
+	stats_check_required_arg(fcinfo, cleararginfo, C_ATTNAME_ARG);
+	attname = PG_GETARG_NAME(C_ATTNAME_ARG);
 	attnum = get_attnum(reloid, NameStr(*attname));
 
 	if (attnum < 0)
@@ -884,13 +932,39 @@ pg_clear_attribute_stats(PG_FUNCTION_ARGS)
 				 errmsg("column \"%s\" of relation \"%s\" does not exist",
 						NameStr(*attname), get_rel_name(reloid))));
 
-	stats_check_required_arg(fcinfo, attarginfo, INHERITED_ARG);
-	inherited = PG_GETARG_BOOL(INHERITED_ARG);
+	stats_check_required_arg(fcinfo, cleararginfo, C_INHERITED_ARG);
+	inherited = PG_GETARG_BOOL(C_INHERITED_ARG);
 
 	delete_pg_statistic(reloid, attnum, inherited);
 	PG_RETURN_VOID();
 }
 
+/*
+ * Import statistics for a given relation attribute.
+ *
+ * Inserts or replaces a row in pg_statistic for the given relation and
+ * attribute name or number. It takes input parameters that correspond to
+ * columns in the view pg_stats.
+ *
+ * Parameters are given in a pseudo named-attribute style: they must be
+ * pairs of parameter names (as text) and values (of appropriate types).
+ * We do that, rather than using regular named-parameter notation, so
+ * that we can add or change parameters without fear of breaking
+ * carelessly-written calls.
+ *
+ * Parameters null_frac, avg_width, and n_distinct all correspond to NOT NULL
+ * columns in pg_statistic. The remaining parameters all belong to a specific
+ * stakind. Some stakinds require multiple parameters, which must be specified
+ * together (or neither specified).
+ *
+ * Parameters are only superficially validated. Omitting a parameter or
+ * passing NULL leaves the statistic unchanged.
+ *
+ * Parameters corresponding to ANYARRAY columns are instead passed in as text
+ * values, which is a valid input string for an array of the type or element
+ * type of the attribute. Any error generated by the array_in() function will
+ * in turn fail the function.
+ */
 Datum
 pg_restore_attribute_stats(PG_FUNCTION_ARGS)
 {