collationcmds.c File Reference

#include "postgres.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "access/xact.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "commands/alter.h"
#include "commands/collationcmds.h"
#include "commands/comment.h"
#include "commands/dbcommands.h"
#include "commands/defrem.h"
#include "common/string.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"
#include "utils/rel.h"
#include "utils/syscache.h"

Include dependency graph for collationcmds.c:

Go to the source code of this file.

Data Structures
struct	CollAliasData

Functions
ObjectAddress	DefineCollation (ParseState *pstate, List *names, List *parameters, bool if_not_exists)
void	IsThereCollationInNamespace (const char *collname, Oid nspOid)
ObjectAddress	AlterCollation (AlterCollationStmt *stmt)
Datum	pg_collation_actual_version (PG_FUNCTION_ARGS)
Datum	pg_import_system_collations (PG_FUNCTION_ARGS)

Function Documentation

AlterCollation()

ObjectAddress AlterCollation

(

AlterCollationStmt *

stmt

)

Definition at line 355 of file collationcmds.c.

{
    Relation    rel;
    Oid         collOid;
    HeapTuple   tup;
    Form_pg_collation collForm;
    Datum       datum;
    bool        isnull;
    char       *oldversion;
    char       *newversion;
    ObjectAddress address;
 
    rel = table_open(CollationRelationId, RowExclusiveLock);
    collOid = get_collation_oid(stmt->collname, false);
 
    if (collOid == DEFAULT_COLLATION_OID)
        ereport(ERROR,
                (errmsg("cannot refresh version of default collation"),
                 errhint("Use ALTER DATABASE ... REFRESH COLLATION VERSION instead.")));
 
    if (!object_ownercheck(CollationRelationId, collOid, GetUserId()))
        aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_COLLATION,
                       NameListToString(stmt->collname));
 
    tup = SearchSysCacheCopy1(COLLOID, ObjectIdGetDatum(collOid));
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "cache lookup failed for collation %u", collOid);
 
    collForm = (Form_pg_collation) GETSTRUCT(tup);
    datum = SysCacheGetAttr(COLLOID, tup, Anum_pg_collation_collversion, &isnull);
    oldversion = isnull ? NULL : TextDatumGetCString(datum);
 
    datum = SysCacheGetAttr(COLLOID, tup, collForm->collprovider == COLLPROVIDER_ICU ? Anum_pg_collation_colliculocale : Anum_pg_collation_collcollate, &isnull);
    if (isnull)
        elog(ERROR, "unexpected null in pg_collation");
    newversion = get_collation_actual_version(collForm->collprovider, TextDatumGetCString(datum));
 
    /* cannot change from NULL to non-NULL or vice versa */
    if ((!oldversion && newversion) || (oldversion && !newversion))
        elog(ERROR, "invalid collation version change");
    else if (oldversion && newversion && strcmp(newversion, oldversion) != 0)
    {
        bool        nulls[Natts_pg_collation];
        bool        replaces[Natts_pg_collation];
        Datum       values[Natts_pg_collation];
 
        ereport(NOTICE,
                (errmsg("changing version from %s to %s",
                        oldversion, newversion)));
 
        memset(values, 0, sizeof(values));
        memset(nulls, false, sizeof(nulls));
        memset(replaces, false, sizeof(replaces));
 
        values[Anum_pg_collation_collversion - 1] = CStringGetTextDatum(newversion);
        replaces[Anum_pg_collation_collversion - 1] = true;
 
        tup = heap_modify_tuple(tup, RelationGetDescr(rel),
                                values, nulls, replaces);
    }
    else
        ereport(NOTICE,
                (errmsg("version has not changed")));
 
    CatalogTupleUpdate(rel, &tup->t_self, tup);
 
    InvokeObjectPostAlterHook(CollationRelationId, collOid, 0);
 
    ObjectAddressSet(address, CollationRelationId, collOid);
 
    heap_freetuple(tup);
    table_close(rel, NoLock);
 
    return address;
}

References aclcheck_error(), ACLCHECK_NOT_OWNER, CatalogTupleUpdate(), AlterCollationStmt::collname, COLLOID, CStringGetTextDatum, elog(), ereport, errhint(), errmsg(), ERROR, get_collation_actual_version(), get_collation_oid(), GETSTRUCT, GetUserId(), heap_freetuple(), heap_modify_tuple(), HeapTupleIsValid, InvokeObjectPostAlterHook, NameListToString(), NoLock, NOTICE, OBJECT_COLLATION, object_ownercheck(), ObjectAddressSet, ObjectIdGetDatum(), RelationGetDescr, RowExclusiveLock, SearchSysCacheCopy1, SysCacheGetAttr(), HeapTupleData::t_self, table_close(), table_open(), TextDatumGetCString, and values.

Referenced by ProcessUtilitySlow().

DefineCollation()

ObjectAddress DefineCollation	(	ParseState *	pstate,
		List *	names,
		List *	parameters,
		bool	if_not_exists
	)

Definition at line 55 of file collationcmds.c.

{
    char       *collName;
    Oid         collNamespace;
    AclResult   aclresult;
    ListCell   *pl;
    DefElem    *fromEl = NULL;
    DefElem    *localeEl = NULL;
    DefElem    *lccollateEl = NULL;
    DefElem    *lcctypeEl = NULL;
    DefElem    *providerEl = NULL;
    DefElem    *deterministicEl = NULL;
    DefElem    *versionEl = NULL;
    char       *collcollate;
    char       *collctype;
    char       *colliculocale;
    bool        collisdeterministic;
    int         collencoding;
    char        collprovider;
    char       *collversion = NULL;
    Oid         newoid;
    ObjectAddress address;
 
    collNamespace = QualifiedNameGetCreationNamespace(names, &collName);
 
    aclresult = object_aclcheck(NamespaceRelationId, collNamespace, GetUserId(), ACL_CREATE);
    if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, OBJECT_SCHEMA,
                       get_namespace_name(collNamespace));
 
    foreach(pl, parameters)
    {
        DefElem    *defel = lfirst_node(DefElem, pl);
        DefElem   **defelp;
 
        if (strcmp(defel->defname, "from") == 0)
            defelp = &fromEl;
        else if (strcmp(defel->defname, "locale") == 0)
            defelp = &localeEl;
        else if (strcmp(defel->defname, "lc_collate") == 0)
            defelp = &lccollateEl;
        else if (strcmp(defel->defname, "lc_ctype") == 0)
            defelp = &lcctypeEl;
        else if (strcmp(defel->defname, "provider") == 0)
            defelp = &providerEl;
        else if (strcmp(defel->defname, "deterministic") == 0)
            defelp = &deterministicEl;
        else if (strcmp(defel->defname, "version") == 0)
            defelp = &versionEl;
        else
        {
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     errmsg("collation attribute \"%s\" not recognized",
                            defel->defname),
                     parser_errposition(pstate, defel->location)));
            break;
        }
        if (*defelp != NULL)
            errorConflictingDefElem(defel, pstate);
        *defelp = defel;
    }
 
    if (localeEl && (lccollateEl || lcctypeEl))
        ereport(ERROR,
                errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("conflicting or redundant options"),
                errdetail("LOCALE cannot be specified together with LC_COLLATE or LC_CTYPE."));
 
    if (fromEl && list_length(parameters) != 1)
        ereport(ERROR,
                errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("conflicting or redundant options"),
                errdetail("FROM cannot be specified together with any other options."));
 
    if (fromEl)
    {
        Oid         collid;
        HeapTuple   tp;
        Datum       datum;
        bool        isnull;
 
        collid = get_collation_oid(defGetQualifiedName(fromEl), false);
        tp = SearchSysCache1(COLLOID, ObjectIdGetDatum(collid));
        if (!HeapTupleIsValid(tp))
            elog(ERROR, "cache lookup failed for collation %u", collid);
 
        collprovider = ((Form_pg_collation) GETSTRUCT(tp))->collprovider;
        collisdeterministic = ((Form_pg_collation) GETSTRUCT(tp))->collisdeterministic;
        collencoding = ((Form_pg_collation) GETSTRUCT(tp))->collencoding;
 
        datum = SysCacheGetAttr(COLLOID, tp, Anum_pg_collation_collcollate, &isnull);
        if (!isnull)
            collcollate = TextDatumGetCString(datum);
        else
            collcollate = NULL;
 
        datum = SysCacheGetAttr(COLLOID, tp, Anum_pg_collation_collctype, &isnull);
        if (!isnull)
            collctype = TextDatumGetCString(datum);
        else
            collctype = NULL;
 
        datum = SysCacheGetAttr(COLLOID, tp, Anum_pg_collation_colliculocale, &isnull);
        if (!isnull)
            colliculocale = TextDatumGetCString(datum);
        else
            colliculocale = NULL;
 
        ReleaseSysCache(tp);
 
        /*
         * Copying the "default" collation is not allowed because most code
         * checks for DEFAULT_COLLATION_OID instead of COLLPROVIDER_DEFAULT,
         * and so having a second collation with COLLPROVIDER_DEFAULT would
         * not work and potentially confuse or crash some code.  This could be
         * fixed with some legwork.
         */
        if (collprovider == COLLPROVIDER_DEFAULT)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                     errmsg("collation \"default\" cannot be copied")));
    }
    else
    {
        char       *collproviderstr = NULL;
 
        collcollate = NULL;
        collctype = NULL;
        colliculocale = NULL;
 
        if (providerEl)
            collproviderstr = defGetString(providerEl);
 
        if (deterministicEl)
            collisdeterministic = defGetBoolean(deterministicEl);
        else
            collisdeterministic = true;
 
        if (versionEl)
            collversion = defGetString(versionEl);
 
        if (collproviderstr)
        {
            if (pg_strcasecmp(collproviderstr, "icu") == 0)
                collprovider = COLLPROVIDER_ICU;
            else if (pg_strcasecmp(collproviderstr, "libc") == 0)
                collprovider = COLLPROVIDER_LIBC;
            else
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("unrecognized collation provider: %s",
                                collproviderstr)));
        }
        else
            collprovider = COLLPROVIDER_LIBC;
 
        if (localeEl)
        {
            if (collprovider == COLLPROVIDER_LIBC)
            {
                collcollate = defGetString(localeEl);
                collctype = defGetString(localeEl);
            }
            else
                colliculocale = defGetString(localeEl);
        }
 
        if (lccollateEl)
            collcollate = defGetString(lccollateEl);
 
        if (lcctypeEl)
            collctype = defGetString(lcctypeEl);
 
        if (collprovider == COLLPROVIDER_LIBC)
        {
            if (!collcollate)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("parameter \"lc_collate\" must be specified")));
 
            if (!collctype)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("parameter \"lc_ctype\" must be specified")));
        }
        else if (collprovider == COLLPROVIDER_ICU)
        {
            if (!colliculocale)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("parameter \"locale\" must be specified")));
        }
 
        /*
         * Nondeterministic collations are currently only supported with ICU
         * because that's the only case where it can actually make a
         * difference. So we can save writing the code for the other
         * providers.
         */
        if (!collisdeterministic && collprovider != COLLPROVIDER_ICU)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("nondeterministic collations not supported with this provider")));
 
        if (collprovider == COLLPROVIDER_ICU)
        {
#ifdef USE_ICU
            /*
             * We could create ICU collations with collencoding == database
             * encoding, but it seems better to use -1 so that it matches the
             * way initdb would create ICU collations.  However, only allow
             * one to be created when the current database's encoding is
             * supported.  Otherwise the collation is useless, plus we get
             * surprising behaviors like not being able to drop the collation.
             *
             * Skip this test when !USE_ICU, because the error we want to
             * throw for that isn't thrown till later.
             */
            if (!is_encoding_supported_by_icu(GetDatabaseEncoding()))
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("current database's encoding is not supported with this provider")));
#endif
            collencoding = -1;
        }
        else
        {
            collencoding = GetDatabaseEncoding();
            check_encoding_locale_matches(collencoding, collcollate, collctype);
        }
    }
 
    if (!collversion)
        collversion = get_collation_actual_version(collprovider, collprovider == COLLPROVIDER_ICU ? colliculocale : collcollate);
 
    newoid = CollationCreate(collName,
                             collNamespace,
                             GetUserId(),
                             collprovider,
                             collisdeterministic,
                             collencoding,
                             collcollate,
                             collctype,
                             colliculocale,
                             collversion,
                             if_not_exists,
                             false);    /* not quiet */
 
    if (!OidIsValid(newoid))
        return InvalidObjectAddress;
 
    /*
     * Check that the locales can be loaded.  NB: pg_newlocale_from_collation
     * is only supposed to be called on non-C-equivalent locales.
     */
    CommandCounterIncrement();
    if (!lc_collate_is_c(newoid) || !lc_ctype_is_c(newoid))
        (void) pg_newlocale_from_collation(newoid);
 
    ObjectAddressSet(address, CollationRelationId, newoid);
 
    return address;
}

References ACL_CREATE, aclcheck_error(), ACLCHECK_OK, check_encoding_locale_matches(), CollationCreate(), COLLOID, CommandCounterIncrement(), defGetBoolean(), defGetQualifiedName(), defGetString(), DefElem::defname, elog(), ereport, errcode(), errdetail(), errmsg(), ERROR, errorConflictingDefElem(), get_collation_actual_version(), get_collation_oid(), get_namespace_name(), GetDatabaseEncoding(), GETSTRUCT, GetUserId(), HeapTupleIsValid, InvalidObjectAddress, is_encoding_supported_by_icu(), lc_collate_is_c(), lc_ctype_is_c(), lfirst_node, list_length(), DefElem::location, object_aclcheck(), OBJECT_SCHEMA, ObjectAddressSet, ObjectIdGetDatum(), OidIsValid, parser_errposition(), pg_newlocale_from_collation(), pg_strcasecmp(), QualifiedNameGetCreationNamespace(), ReleaseSysCache(), SearchSysCache1(), SysCacheGetAttr(), and TextDatumGetCString.

Referenced by ProcessUtilitySlow().

IsThereCollationInNamespace()

void IsThereCollationInNamespace	(	const char *	collname,
		Oid	nspOid
	)

Definition at line 327 of file collationcmds.c.

{
    /* make sure the name doesn't already exist in new schema */
    if (SearchSysCacheExists3(COLLNAMEENCNSP,
                              CStringGetDatum(collname),
                              Int32GetDatum(GetDatabaseEncoding()),
                              ObjectIdGetDatum(nspOid)))
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("collation \"%s\" for encoding \"%s\" already exists in schema \"%s\"",
                        collname, GetDatabaseEncodingName(),
                        get_namespace_name(nspOid))));
 
    /* mustn't match an any-encoding entry, either */
    if (SearchSysCacheExists3(COLLNAMEENCNSP,
                              CStringGetDatum(collname),
                              Int32GetDatum(-1),
                              ObjectIdGetDatum(nspOid)))
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("collation \"%s\" already exists in schema \"%s\"",
                        collname, get_namespace_name(nspOid))));
}

References COLLNAMEENCNSP, CStringGetDatum(), ereport, errcode(), ERRCODE_DUPLICATE_OBJECT, errmsg(), ERROR, get_namespace_name(), GetDatabaseEncoding(), GetDatabaseEncodingName(), Int32GetDatum(), ObjectIdGetDatum(), and SearchSysCacheExists3.

Referenced by AlterObjectNamespace_internal(), and AlterObjectRename_internal().

pg_collation_actual_version()

Datum pg_collation_actual_version

(

PG_FUNCTION_ARGS

)

Definition at line 433 of file collationcmds.c.

{
    Oid      collid = PG_GETARG_OID(0);
    char     provider;
    char    *locale;
    char    *version;
    Datum    datum;
    bool     isnull;
 
    if (collid == DEFAULT_COLLATION_OID)
    {
        /* retrieve from pg_database */
 
        HeapTuple   dbtup = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(MyDatabaseId));
        if (!HeapTupleIsValid(dbtup))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("database with OID %u does not exist", MyDatabaseId)));
 
        provider = ((Form_pg_database) GETSTRUCT(dbtup))->datlocprovider;
 
        datum = SysCacheGetAttr(DATABASEOID, dbtup,
                                provider == COLLPROVIDER_ICU ?
                                Anum_pg_database_daticulocale : Anum_pg_database_datcollate,
                                &isnull);
        if (isnull)
            elog(ERROR, "unexpected null in pg_database");
 
        locale = TextDatumGetCString(datum);
 
        ReleaseSysCache(dbtup);
    }
    else
    {
        /* retrieve from pg_collation */
 
        HeapTuple   colltp      = SearchSysCache1(COLLOID, ObjectIdGetDatum(collid));
        if (!HeapTupleIsValid(colltp))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("collation with OID %u does not exist", collid)));
 
        provider = ((Form_pg_collation) GETSTRUCT(colltp))->collprovider;
        Assert(provider != COLLPROVIDER_DEFAULT);
        datum = SysCacheGetAttr(COLLOID, colltp,
                                provider == COLLPROVIDER_ICU ?
                                Anum_pg_collation_colliculocale : Anum_pg_collation_collcollate,
                                &isnull);
        if (isnull)
            elog(ERROR, "unexpected null in pg_collation");
 
        locale = TextDatumGetCString(datum);
 
        ReleaseSysCache(colltp);
    }
 
    version = get_collation_actual_version(provider, locale);
    if (version)
        PG_RETURN_TEXT_P(cstring_to_text(version));
    else
        PG_RETURN_NULL();
}

References Assert(), COLLOID, cstring_to_text(), DATABASEOID, datlocprovider, elog(), ereport, errcode(), errmsg(), ERROR, get_collation_actual_version(), GETSTRUCT, HeapTupleIsValid, locale, MyDatabaseId, ObjectIdGetDatum(), PG_GETARG_OID, PG_RETURN_NULL, PG_RETURN_TEXT_P, provider, ReleaseSysCache(), SearchSysCache1(), SysCacheGetAttr(), and TextDatumGetCString.

pg_import_system_collations()

Datum pg_import_system_collations

(

PG_FUNCTION_ARGS

)

Definition at line 617 of file collationcmds.c.

{
    Oid         nspid = PG_GETARG_OID(0);
    int         ncreated = 0;
 
    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to import system collations")));
 
    if (!SearchSysCacheExists1(NAMESPACEOID, ObjectIdGetDatum(nspid)))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_SCHEMA),
                 errmsg("schema with OID %u does not exist", nspid)));
 
    /* Load collations known to libc, using "locale -a" to enumerate them */
#ifdef READ_LOCALE_A_OUTPUT
    {
        FILE       *locale_a_handle;
        char        localebuf[LOCALE_NAME_BUFLEN];
        int         nvalid = 0;
        Oid         collid;
        CollAliasData *aliases;
        int         naliases,
                    maxaliases,
                    i;
 
        /* expansible array of aliases */
        maxaliases = 100;
        aliases = (CollAliasData *) palloc(maxaliases * sizeof(CollAliasData));
        naliases = 0;
 
        locale_a_handle = OpenPipeStream("locale -a", "r");
        if (locale_a_handle == NULL)
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not execute command \"%s\": %m",
                            "locale -a")));
 
        while (fgets(localebuf, sizeof(localebuf), locale_a_handle))
        {
            size_t      len;
            int         enc;
            char        alias[LOCALE_NAME_BUFLEN];
 
            len = strlen(localebuf);
 
            if (len == 0 || localebuf[len - 1] != '\n')
            {
                elog(DEBUG1, "skipping locale with too-long name: \"%s\"", localebuf);
                continue;
            }
            localebuf[len - 1] = '\0';
 
            /*
             * Some systems have locale names that don't consist entirely of
             * ASCII letters (such as "bokmål" or "français").
             * This is pretty silly, since we need the locale itself to
             * interpret the non-ASCII characters. We can't do much with
             * those, so we filter them out.
             */
            if (!pg_is_ascii(localebuf))
            {
                elog(DEBUG1, "skipping locale with non-ASCII name: \"%s\"", localebuf);
                continue;
            }
 
            enc = pg_get_encoding_from_locale(localebuf, false);
            if (enc < 0)
            {
                elog(DEBUG1, "skipping locale with unrecognized encoding: \"%s\"",
                     localebuf);
                continue;
            }
            if (!PG_VALID_BE_ENCODING(enc))
            {
                elog(DEBUG1, "skipping locale with client-only encoding: \"%s\"", localebuf);
                continue;
            }
            if (enc == PG_SQL_ASCII)
                continue;       /* C/POSIX are already in the catalog */
 
            /* count valid locales found in operating system */
            nvalid++;
 
            /*
             * Create a collation named the same as the locale, but quietly
             * doing nothing if it already exists.  This is the behavior we
             * need even at initdb time, because some versions of "locale -a"
             * can report the same locale name more than once.  And it's
             * convenient for later import runs, too, since you just about
             * always want to add on new locales without a lot of chatter
             * about existing ones.
             */
            collid = CollationCreate(localebuf, nspid, GetUserId(),
                                     COLLPROVIDER_LIBC, true, enc,
                                     localebuf, localebuf, NULL,
                                     get_collation_actual_version(COLLPROVIDER_LIBC, localebuf),
                                     true, true);
            if (OidIsValid(collid))
            {
                ncreated++;
 
                /* Must do CCI between inserts to handle duplicates correctly */
                CommandCounterIncrement();
            }
 
            /*
             * Generate aliases such as "en_US" in addition to "en_US.utf8"
             * for ease of use.  Note that collation names are unique per
             * encoding only, so this doesn't clash with "en_US" for LATIN1,
             * say.
             *
             * However, it might conflict with a name we'll see later in the
             * "locale -a" output.  So save up the aliases and try to add them
             * after we've read all the output.
             */
            if (normalize_libc_locale_name(alias, localebuf))
            {
                if (naliases >= maxaliases)
                {
                    maxaliases *= 2;
                    aliases = (CollAliasData *)
                        repalloc(aliases, maxaliases * sizeof(CollAliasData));
                }
                aliases[naliases].localename = pstrdup(localebuf);
                aliases[naliases].alias = pstrdup(alias);
                aliases[naliases].enc = enc;
                naliases++;
            }
        }
 
        /*
         * We don't check the return value of this, because we want to support
         * the case where there "locale" command does not exist.  (This is
         * unusual but can happen on minimalized Linux distributions, for
         * example.)  We will warn below if no locales could be found.
         */
        ClosePipeStream(locale_a_handle);
 
        /*
         * Before processing the aliases, sort them by locale name.  The point
         * here is that if "locale -a" gives us multiple locale names with the
         * same encoding and base name, say "en_US.utf8" and "en_US.utf-8", we
         * want to pick a deterministic one of them.  First in ASCII sort
         * order is a good enough rule.  (Before PG 10, the code corresponding
         * to this logic in initdb.c had an additional ordering rule, to
         * prefer the locale name exactly matching the alias, if any.  We
         * don't need to consider that here, because we would have already
         * created such a pg_collation entry above, and that one will win.)
         */
        if (naliases > 1)
            qsort((void *) aliases, naliases, sizeof(CollAliasData), cmpaliases);
 
        /* Now add aliases, ignoring any that match pre-existing entries */
        for (i = 0; i < naliases; i++)
        {
            char       *locale = aliases[i].localename;
            char       *alias = aliases[i].alias;
            int         enc = aliases[i].enc;
 
            collid = CollationCreate(alias, nspid, GetUserId(),
                                     COLLPROVIDER_LIBC, true, enc,
                                     locale, locale, NULL,
                                     get_collation_actual_version(COLLPROVIDER_LIBC, locale),
                                     true, true);
            if (OidIsValid(collid))
            {
                ncreated++;
 
                CommandCounterIncrement();
            }
        }
 
        /* Give a warning if "locale -a" seems to be malfunctioning */
        if (nvalid == 0)
            ereport(WARNING,
                    (errmsg("no usable system locales were found")));
    }
#endif                          /* READ_LOCALE_A_OUTPUT */
 
    /*
     * Load collations known to ICU
     *
     * We use uloc_countAvailable()/uloc_getAvailable() rather than
     * ucol_countAvailable()/ucol_getAvailable().  The former returns a full
     * set of language+region combinations, whereas the latter only returns
     * language+region combinations if they are distinct from the language's
     * base collation.  So there might not be a de-DE or en-GB, which would be
     * confusing.
     */
#ifdef USE_ICU
    {
        int         i;
 
        /*
         * Start the loop at -1 to sneak in the root locale without too much
         * code duplication.
         */
        for (i = -1; i < uloc_countAvailable(); i++)
        {
            const char *name;
            char       *langtag;
            char       *icucomment;
            const char *iculocstr;
            Oid         collid;
 
            if (i == -1)
                name = "";      /* ICU root locale */
            else
                name = uloc_getAvailable(i);
 
            langtag = get_icu_language_tag(name);
            iculocstr = U_ICU_VERSION_MAJOR_NUM >= 54 ? langtag : name;
 
            /*
             * Be paranoid about not allowing any non-ASCII strings into
             * pg_collation
             */
            if (!pg_is_ascii(langtag) || !pg_is_ascii(iculocstr))
                continue;
 
            collid = CollationCreate(psprintf("%s-x-icu", langtag),
                                     nspid, GetUserId(),
                                     COLLPROVIDER_ICU, true, -1,
                                     NULL, NULL, iculocstr,
                                     get_collation_actual_version(COLLPROVIDER_ICU, iculocstr),
                                     true, true);
            if (OidIsValid(collid))
            {
                ncreated++;
 
                CommandCounterIncrement();
 
                icucomment = get_icu_locale_comment(name);
                if (icucomment)
                    CreateComments(collid, CollationRelationId, 0,
                                   icucomment);
            }
        }
    }
#endif                          /* USE_ICU */
 
    PG_RETURN_INT32(ncreated);
}

References CollAliasData::alias, ClosePipeStream(), CollationCreate(), CommandCounterIncrement(), CreateComments(), DEBUG1, elog(), CollAliasData::enc, enc, ereport, errcode(), errcode_for_file_access(), errmsg(), ERROR, get_collation_actual_version(), GetUserId(), i, len, locale, LOCALE_NAME_BUFLEN, CollAliasData::localename, name, NAMESPACEOID, ObjectIdGetDatum(), OidIsValid, OpenPipeStream(), palloc(), pg_get_encoding_from_locale(), PG_GETARG_OID, pg_is_ascii(), PG_RETURN_INT32, PG_SQL_ASCII, PG_VALID_BE_ENCODING, psprintf(), pstrdup(), qsort, repalloc(), SearchSysCacheExists1, superuser(), and WARNING.