ddlutils.c

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/*-------------------------------------------------------------------------
 *
 * ddlutils.c
 *      Utility functions for generating DDL statements
 *
 * This file contains the pg_get_*_ddl family of functions that generate
 * DDL statements to recreate database objects such as roles, tablespaces,
 * and databases, along with common infrastructure for option parsing and
 * pretty-printing.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/ddlutils.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_database.h"
#include "catalog/pg_db_role_setting.h"
#include "catalog/pg_tablespace.h"
#include "commands/tablespace.h"
#include "common/relpath.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "utils/acl.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/datetime.h"
#include "utils/fmgroids.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"
#include "utils/rel.h"
#include "utils/ruleutils.h"
#include "utils/syscache.h"
#include "utils/timestamp.h"
#include "utils/varlena.h"
 
/* Option value types for DDL option parsing */
typedef enum
{
    DDL_OPT_BOOL,
    DDL_OPT_TEXT,
    DDL_OPT_INT,
} DdlOptType;
 
/*
 * A single DDL option descriptor: caller fills in name and type,
 * parse_ddl_options fills in isset + the appropriate value field.
 */
typedef struct DdlOption
{
    const char *name;           /* option name (case-insensitive match) */
    DdlOptType  type;           /* expected value type */
    bool        isset;          /* true if caller supplied this option */
    /* fields for specific option types */
    union
    {
        bool        boolval;    /* filled in for DDL_OPT_BOOL */
        char       *textval;    /* filled in for DDL_OPT_TEXT (palloc'd) */
        int         intval;     /* filled in for DDL_OPT_INT */
    };
} DdlOption;
 
 
static void parse_ddl_options(FunctionCallInfo fcinfo, int variadic_start,
                              DdlOption *opts, int nopts);
static void append_ddl_option(StringInfo buf, bool pretty, int indent,
                              const char *fmt,...)
            pg_attribute_printf(4, 5);
static void append_guc_value(StringInfo buf, const char *name,
                             const char *value);
static List *pg_get_role_ddl_internal(Oid roleid, bool pretty,
                                      bool memberships);
static List *pg_get_tablespace_ddl_internal(Oid tsid, bool pretty, bool no_owner);
static Datum pg_get_tablespace_ddl_srf(FunctionCallInfo fcinfo, Oid tsid, bool isnull);
static List *pg_get_database_ddl_internal(Oid dbid, bool pretty,
                                          bool no_owner, bool no_tablespace);
 
 
/*
 * parse_ddl_options
 *      Parse variadic name/value option pairs
 *
 * Options are passed as alternating key/value text pairs.  The caller
 * provides an array of DdlOption descriptors specifying the accepted
 * option names and their types; this function matches each supplied
 * pair against the array, validates the value, and fills in the
 * result fields.
 */
static void
parse_ddl_options(FunctionCallInfo fcinfo, int variadic_start,
                  DdlOption *opts, int nopts)
{
    Datum      *args;
    bool       *nulls;
    Oid        *types;
    int         nargs;
 
    /* Clear all output fields */
    for (int i = 0; i < nopts; i++)
    {
        opts[i].isset = false;
        switch (opts[i].type)
        {
            case DDL_OPT_BOOL:
                opts[i].boolval = false;
                break;
            case DDL_OPT_TEXT:
                opts[i].textval = NULL;
                break;
            case DDL_OPT_INT:
                opts[i].intval = 0;
                break;
        }
    }
 
    nargs = extract_variadic_args(fcinfo, variadic_start, true,
                                  &args, &types, &nulls);
 
    if (nargs <= 0)
        return;
 
    /* Handle DEFAULT NULL case */
    if (nargs == 1 && nulls[0])
        return;
 
    if (nargs % 2 != 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("variadic arguments must be name/value pairs"),
                 errhint("Provide an even number of variadic arguments that can be divided into pairs.")));
 
    /*
     * For each option name/value pair, find corresponding positional option
     * for the option name, and assign the option value.
     */
    for (int i = 0; i < nargs; i += 2)
    {
        char       *name;
        char       *valstr;
        DdlOption  *opt = NULL;
 
        if (nulls[i])
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("option name at variadic position %d is null", i + 1)));
 
        name = TextDatumGetCString(args[i]);
 
        if (nulls[i + 1])
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("value for option \"%s\" must not be null", name)));
 
        /* Find matching option descriptor */
        for (int j = 0; j < nopts; j++)
        {
            if (pg_strcasecmp(name, opts[j].name) == 0)
            {
                opt = &opts[j];
                break;
            }
        }
 
        if (opt == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("unrecognized option: \"%s\"", name)));
 
        if (opt->isset)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("option \"%s\" is specified more than once",
                            name)));
 
        valstr = TextDatumGetCString(args[i + 1]);
 
        switch (opt->type)
        {
            case DDL_OPT_BOOL:
                if (!parse_bool(valstr, &opt->boolval))
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("invalid value for boolean option \"%s\": %s",
                                    name, valstr)));
                break;
 
            case DDL_OPT_TEXT:
                opt->textval = valstr;
                valstr = NULL;  /* don't pfree below */
                break;
 
            case DDL_OPT_INT:
                {
                    char       *endp;
                    long        val;
 
                    errno = 0;
                    val = strtol(valstr, &endp, 10);
                    if (*endp != '\0' || errno == ERANGE ||
                        val < PG_INT32_MIN || val > PG_INT32_MAX)
                        ereport(ERROR,
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                 errmsg("invalid value for integer option \"%s\": %s",
                                        name, valstr)));
                    opt->intval = (int) val;
                }
                break;
        }
 
        opt->isset = true;
 
        if (valstr)
            pfree(valstr);
        pfree(name);
    }
}
 
/*
 * Helper to append a formatted string with optional pretty-printing.
 */
static void
append_ddl_option(StringInfo buf, bool pretty, int indent,
                  const char *fmt,...)
{
    if (pretty)
    {
        appendStringInfoChar(buf, '\n');
        appendStringInfoSpaces(buf, indent);
    }
    else
        appendStringInfoChar(buf, ' ');
 
    for (;;)
    {
        va_list     args;
        int         needed;
 
        va_start(args, fmt);
        needed = appendStringInfoVA(buf, fmt, args);
        va_end(args);
        if (needed == 0)
            break;
        enlargeStringInfo(buf, needed);
    }
}
 
/*
 * append_guc_value
 *      Append a GUC setting value to buf, handling GUC_LIST_QUOTE properly.
 *
 * Variables marked GUC_LIST_QUOTE were already fully quoted before they
 * were stored in the setconfig array.  We break the list value apart
 * and re-quote the elements as string literals.  For all other variables
 * we simply quote the value as a single string literal.
 *
 * The caller has already appended "SET <name> TO " to buf.
 */
static void
append_guc_value(StringInfo buf, const char *name, const char *value)
{
    char       *rawval;
 
    rawval = pstrdup(value);
 
    if (GetConfigOptionFlags(name, true) & GUC_LIST_QUOTE)
    {
        List       *namelist;
        bool        first = true;
 
        /* Parse string into list of identifiers */
        if (!SplitGUCList(rawval, ',', &namelist))
        {
            /* this shouldn't fail really */
            elog(ERROR, "invalid list syntax in setconfig item");
        }
        /* Special case: represent an empty list as NULL */
        if (namelist == NIL)
            appendStringInfoString(buf, "NULL");
        foreach_ptr(char, curname, namelist)
        {
            if (first)
                first = false;
            else
                appendStringInfoString(buf, ", ");
            appendStringInfoString(buf, quote_literal_cstr(curname));
        }
        list_free(namelist);
    }
    else
        appendStringInfoString(buf, quote_literal_cstr(rawval));
 
    pfree(rawval);
}
 
/*
 * pg_get_role_ddl_internal
 *      Generate DDL statements to recreate a role
 *
 * Returns a List of palloc'd strings, each being a complete SQL statement.
 * The first list element is always the CREATE ROLE statement; subsequent
 * elements are ALTER ROLE SET statements for any role-specific or
 * role-in-database configuration settings.  If memberships is true,
 * GRANT statements for role memberships are appended.
 */
static List *
pg_get_role_ddl_internal(Oid roleid, bool pretty, bool memberships)
{
    HeapTuple   tuple;
    Form_pg_authid roleform;
    StringInfoData buf;
    char       *rolname;
    Datum       rolevaliduntil;
    bool        isnull;
    Relation    rel;
    ScanKeyData scankey;
    SysScanDesc scan;
    List       *statements = NIL;
 
    tuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(roleid));
    if (!HeapTupleIsValid(tuple))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("role with OID %u does not exist", roleid)));
 
    roleform = (Form_pg_authid) GETSTRUCT(tuple);
    rolname = pstrdup(NameStr(roleform->rolname));
 
    /* User must have SELECT privilege on pg_authid. */
    if (pg_class_aclcheck(AuthIdRelationId, GetUserId(), ACL_SELECT) != ACLCHECK_OK)
    {
        ReleaseSysCache(tuple);
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied for role %s", rolname)));
    }
 
    /*
     * We don't support generating DDL for system roles.  The primary reason
     * for this is that users shouldn't be recreating them.
     */
    if (IsReservedName(rolname))
        ereport(ERROR,
                (errcode(ERRCODE_RESERVED_NAME),
                 errmsg("role name \"%s\" is reserved", rolname),
                 errdetail("Role names starting with \"pg_\" are reserved for system roles.")));
 
    initStringInfo(&buf);
    appendStringInfo(&buf, "CREATE ROLE %s", quote_identifier(rolname));
 
    /*
     * Append role attributes.  The order here follows the same sequence as
     * you'd typically write them in a CREATE ROLE command, though any order
     * is actually acceptable to the parser.
     */
    append_ddl_option(&buf, pretty, 4, "%s",
                      roleform->rolsuper ? "SUPERUSER" : "NOSUPERUSER");
 
    append_ddl_option(&buf, pretty, 4, "%s",
                      roleform->rolinherit ? "INHERIT" : "NOINHERIT");
 
    append_ddl_option(&buf, pretty, 4, "%s",
                      roleform->rolcreaterole ? "CREATEROLE" : "NOCREATEROLE");
 
    append_ddl_option(&buf, pretty, 4, "%s",
                      roleform->rolcreatedb ? "CREATEDB" : "NOCREATEDB");
 
    append_ddl_option(&buf, pretty, 4, "%s",
                      roleform->rolcanlogin ? "LOGIN" : "NOLOGIN");
 
    append_ddl_option(&buf, pretty, 4, "%s",
                      roleform->rolreplication ? "REPLICATION" : "NOREPLICATION");
 
    append_ddl_option(&buf, pretty, 4, "%s",
                      roleform->rolbypassrls ? "BYPASSRLS" : "NOBYPASSRLS");
 
    /*
     * CONNECTION LIMIT is only interesting if it's not -1 (the default,
     * meaning no limit).
     */
    if (roleform->rolconnlimit >= 0)
        append_ddl_option(&buf, pretty, 4, "CONNECTION LIMIT %d",
                          roleform->rolconnlimit);
 
    rolevaliduntil = SysCacheGetAttr(AUTHOID, tuple,
                                     Anum_pg_authid_rolvaliduntil,
                                     &isnull);
    if (!isnull)
    {
        TimestampTz ts;
        int         tz;
        struct pg_tm tm;
        fsec_t      fsec;
        const char *tzn;
        char        ts_str[MAXDATELEN + 1];
 
        ts = DatumGetTimestampTz(rolevaliduntil);
        if (TIMESTAMP_NOT_FINITE(ts))
            EncodeSpecialTimestamp(ts, ts_str);
        else if (timestamp2tm(ts, &tz, &tm, &fsec, &tzn, NULL) == 0)
            EncodeDateTime(&tm, fsec, true, tz, tzn, USE_ISO_DATES, ts_str);
        else
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));
 
        append_ddl_option(&buf, pretty, 4, "VALID UNTIL %s",
                          quote_literal_cstr(ts_str));
    }
 
    ReleaseSysCache(tuple);
 
    /*
     * We intentionally omit PASSWORD.  There's no way to retrieve the
     * original password text from the stored hash, and even if we could,
     * exposing passwords through a SQL function would be a security issue.
     * Users must set passwords separately after recreating roles.
     */
 
    appendStringInfoChar(&buf, ';');
 
    statements = lappend(statements, pstrdup(buf.data));
 
    /*
     * Now scan pg_db_role_setting for ALTER ROLE SET configurations.
     *
     * These can be role-wide (setdatabase = 0) or specific to a particular
     * database (setdatabase = a valid DB OID).  It generates one ALTER
     * statement per setting.
     */
    rel = table_open(DbRoleSettingRelationId, AccessShareLock);
    ScanKeyInit(&scankey,
                Anum_pg_db_role_setting_setrole,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(roleid));
    scan = systable_beginscan(rel, DbRoleSettingDatidRolidIndexId, true,
                              NULL, 1, &scankey);
 
    while (HeapTupleIsValid(tuple = systable_getnext(scan)))
    {
        Form_pg_db_role_setting setting = (Form_pg_db_role_setting) GETSTRUCT(tuple);
        Oid         datid = setting->setdatabase;
        Datum       datum;
        ArrayType  *role_settings;
        Datum      *settings;
        bool       *nulls;
        int         nsettings;
        char       *datname = NULL;
 
        /*
         * If setdatabase is valid, this is a role-in-database setting;
         * otherwise it's a role-wide setting.  Look up the database name once
         * for all settings in this row.
         */
        if (OidIsValid(datid))
        {
            datname = get_database_name(datid);
            /* Database has been dropped; skip all settings in this row. */
            if (datname == NULL)
                continue;
        }
 
        /*
         * The setconfig column is a text array in "name=value" format. It
         * should never be null for a valid row, but be defensive.
         */
        datum = heap_getattr(tuple, Anum_pg_db_role_setting_setconfig,
                             RelationGetDescr(rel), &isnull);
        if (isnull)
            continue;
 
        role_settings = DatumGetArrayTypeP(datum);
 
        deconstruct_array_builtin(role_settings, TEXTOID, &settings, &nulls, &nsettings);
 
        for (int i = 0; i < nsettings; i++)
        {
            char       *s,
                       *p;
 
            if (nulls[i])
                continue;
 
            s = TextDatumGetCString(settings[i]);
            p = strchr(s, '=');
            if (p == NULL)
            {
                pfree(s);
                continue;
            }
            *p++ = '\0';
 
            /* Build a fresh ALTER ROLE statement for this setting */
            resetStringInfo(&buf);
            appendStringInfo(&buf, "ALTER ROLE %s", quote_identifier(rolname));
 
            if (datname != NULL)
                appendStringInfo(&buf, " IN DATABASE %s",
                                 quote_identifier(datname));
 
            appendStringInfo(&buf, " SET %s TO ",
                             quote_identifier(s));
 
            append_guc_value(&buf, s, p);
 
            appendStringInfoChar(&buf, ';');
 
            statements = lappend(statements, pstrdup(buf.data));
 
            pfree(s);
        }
 
        pfree(settings);
        pfree(nulls);
        pfree(role_settings);
 
        if (datname != NULL)
            pfree(datname);
    }
 
    systable_endscan(scan);
    table_close(rel, AccessShareLock);
 
    /*
     * Scan pg_auth_members for role memberships.  We look for rows where
     * member = roleid, meaning this role has been granted membership in other
     * roles.
     */
    if (memberships)
    {
        rel = table_open(AuthMemRelationId, AccessShareLock);
        ScanKeyInit(&scankey,
                    Anum_pg_auth_members_member,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(roleid));
        scan = systable_beginscan(rel, AuthMemMemRoleIndexId, true,
                                  NULL, 1, &scankey);
 
        while (HeapTupleIsValid(tuple = systable_getnext(scan)))
        {
            Form_pg_auth_members memform = (Form_pg_auth_members) GETSTRUCT(tuple);
            char       *granted_role;
            char       *grantor;
 
            granted_role = GetUserNameFromId(memform->roleid, false);
            grantor = GetUserNameFromId(memform->grantor, false);
 
            resetStringInfo(&buf);
            appendStringInfo(&buf, "GRANT %s TO %s",
                             quote_identifier(granted_role),
                             quote_identifier(rolname));
            appendStringInfo(&buf, " WITH ADMIN %s, INHERIT %s, SET %s",
                             memform->admin_option ? "TRUE" : "FALSE",
                             memform->inherit_option ? "TRUE" : "FALSE",
                             memform->set_option ? "TRUE" : "FALSE");
            appendStringInfo(&buf, " GRANTED BY %s;",
                             quote_identifier(grantor));
 
            statements = lappend(statements, pstrdup(buf.data));
 
            pfree(granted_role);
            pfree(grantor);
        }
 
        systable_endscan(scan);
        table_close(rel, AccessShareLock);
    }
 
    pfree(buf.data);
    pfree(rolname);
 
    return statements;
}
 
/*
 * pg_get_role_ddl
 *      Return DDL to recreate a role as a set of text rows.
 *
 * Each row is a complete SQL statement.  The first row is always the
 * CREATE ROLE statement; subsequent rows are ALTER ROLE SET statements
 * and optionally GRANT statements for role memberships.
 * Returns no rows if the role argument is NULL.
 */
Datum
pg_get_role_ddl(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    List       *statements;
 
    if (SRF_IS_FIRSTCALL())
    {
        MemoryContext oldcontext;
        Oid         roleid;
        DdlOption   opts[] = {
            {"pretty", DDL_OPT_BOOL},
            {"memberships", DDL_OPT_BOOL},
        };
 
        funcctx = SRF_FIRSTCALL_INIT();
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
        if (PG_ARGISNULL(0))
        {
            MemoryContextSwitchTo(oldcontext);
            SRF_RETURN_DONE(funcctx);
        }
 
        roleid = PG_GETARG_OID(0);
        parse_ddl_options(fcinfo, 1, opts, lengthof(opts));
 
        statements = pg_get_role_ddl_internal(roleid,
                                              opts[0].isset && opts[0].boolval,
                                              !opts[1].isset || opts[1].boolval);
        funcctx->user_fctx = statements;
        funcctx->max_calls = list_length(statements);
 
        MemoryContextSwitchTo(oldcontext);
    }
 
    funcctx = SRF_PERCALL_SETUP();
    statements = (List *) funcctx->user_fctx;
 
    if (funcctx->call_cntr < funcctx->max_calls)
    {
        char       *stmt;
 
        stmt = list_nth(statements, funcctx->call_cntr);
 
        SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(stmt));
    }
    else
    {
        list_free_deep(statements);
        SRF_RETURN_DONE(funcctx);
    }
}
 
/*
 * pg_get_tablespace_ddl_internal
 *      Generate DDL statements to recreate a tablespace.
 *
 * Returns a List of palloc'd strings.  The first element is the
 * CREATE TABLESPACE statement; if the tablespace has reloptions,
 * a second element with ALTER TABLESPACE SET (...) is appended.
 */
static List *
pg_get_tablespace_ddl_internal(Oid tsid, bool pretty, bool no_owner)
{
    HeapTuple   tuple;
    Form_pg_tablespace tspForm;
    StringInfoData buf;
    char       *spcname;
    char       *spcowner;
    char       *path;
    bool        isNull;
    Datum       datum;
    List       *statements = NIL;
 
    tuple = SearchSysCache1(TABLESPACEOID, ObjectIdGetDatum(tsid));
    if (!HeapTupleIsValid(tuple))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("tablespace with OID %u does not exist",
                        tsid)));
 
    tspForm = (Form_pg_tablespace) GETSTRUCT(tuple);
    spcname = pstrdup(NameStr(tspForm->spcname));
 
    /* User must have SELECT privilege on pg_tablespace. */
    if (pg_class_aclcheck(TableSpaceRelationId, GetUserId(), ACL_SELECT) != ACLCHECK_OK)
    {
        ReleaseSysCache(tuple);
        aclcheck_error(ACLCHECK_NO_PRIV, OBJECT_TABLESPACE, spcname);
    }
 
    /*
     * We don't support generating DDL for system tablespaces.  The primary
     * reason for this is that users shouldn't be recreating them.
     */
    if (IsReservedName(spcname))
        ereport(ERROR,
                (errcode(ERRCODE_RESERVED_NAME),
                 errmsg("tablespace name \"%s\" is reserved", spcname),
                 errdetail("Tablespace names starting with \"pg_\" are reserved for system tablespaces.")));
 
    initStringInfo(&buf);
 
    /* Start building the CREATE TABLESPACE statement */
    appendStringInfo(&buf, "CREATE TABLESPACE %s", quote_identifier(spcname));
 
    /* Add OWNER clause */
    if (!no_owner)
    {
        spcowner = GetUserNameFromId(tspForm->spcowner, false);
        append_ddl_option(&buf, pretty, 4, "OWNER %s",
                          quote_identifier(spcowner));
        pfree(spcowner);
    }
 
    /* Find tablespace directory path */
    path = get_tablespace_location(tsid);
 
    /* Add directory LOCATION (path), if it exists */
    if (path[0] != '\0')
    {
        /*
         * Special case: if the tablespace was created with GUC
         * "allow_in_place_tablespaces = true" and "LOCATION ''", path will
         * begin with "pg_tblspc/". In that case, show "LOCATION ''" as the
         * user originally specified.
         */
        if (strncmp(PG_TBLSPC_DIR_SLASH, path, strlen(PG_TBLSPC_DIR_SLASH)) == 0)
            append_ddl_option(&buf, pretty, 4, "LOCATION ''");
        else
            append_ddl_option(&buf, pretty, 4, "LOCATION %s",
                              quote_literal_cstr(path));
    }
    pfree(path);
 
    appendStringInfoChar(&buf, ';');
    statements = lappend(statements, pstrdup(buf.data));
 
    /* Check for tablespace options */
    datum = SysCacheGetAttr(TABLESPACEOID, tuple,
                            Anum_pg_tablespace_spcoptions, &isNull);
    if (!isNull)
    {
        resetStringInfo(&buf);
        appendStringInfo(&buf, "ALTER TABLESPACE %s SET (",
                         quote_identifier(spcname));
        get_reloptions(&buf, datum);
        appendStringInfoString(&buf, ");");
        statements = lappend(statements, pstrdup(buf.data));
    }
 
    ReleaseSysCache(tuple);
    pfree(spcname);
    pfree(buf.data);
 
    return statements;
}
 
/*
 * pg_get_tablespace_ddl_srf - common SRF logic for tablespace DDL
 */
static Datum
pg_get_tablespace_ddl_srf(FunctionCallInfo fcinfo, Oid tsid, bool isnull)
{
    FuncCallContext *funcctx;
    List       *statements;
 
    if (SRF_IS_FIRSTCALL())
    {
        MemoryContext oldcontext;
        DdlOption   opts[] = {
            {"pretty", DDL_OPT_BOOL},
            {"owner", DDL_OPT_BOOL},
        };
 
        funcctx = SRF_FIRSTCALL_INIT();
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
        if (isnull)
        {
            MemoryContextSwitchTo(oldcontext);
            SRF_RETURN_DONE(funcctx);
        }
 
        parse_ddl_options(fcinfo, 1, opts, lengthof(opts));
 
        statements = pg_get_tablespace_ddl_internal(tsid,
                                                    opts[0].isset && opts[0].boolval,
                                                    opts[1].isset && !opts[1].boolval);
        funcctx->user_fctx = statements;
        funcctx->max_calls = list_length(statements);
 
        MemoryContextSwitchTo(oldcontext);
    }
 
    funcctx = SRF_PERCALL_SETUP();
    statements = (List *) funcctx->user_fctx;
 
    if (funcctx->call_cntr < funcctx->max_calls)
    {
        char       *stmt;
 
        stmt = (char *) list_nth(statements, funcctx->call_cntr);
 
        SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(stmt));
    }
    else
    {
        list_free_deep(statements);
        SRF_RETURN_DONE(funcctx);
    }
}
 
/*
 * pg_get_tablespace_ddl_oid
 *      Return DDL to recreate a tablespace, taking OID.
 */
Datum
pg_get_tablespace_ddl_oid(PG_FUNCTION_ARGS)
{
    Oid         tsid = InvalidOid;
    bool        isnull;
 
    isnull = PG_ARGISNULL(0);
    if (!isnull)
        tsid = PG_GETARG_OID(0);
 
    return pg_get_tablespace_ddl_srf(fcinfo, tsid, isnull);
}
 
/*
 * pg_get_tablespace_ddl_name
 *      Return DDL to recreate a tablespace, taking name.
 */
Datum
pg_get_tablespace_ddl_name(PG_FUNCTION_ARGS)
{
    Oid         tsid = InvalidOid;
    Name        tspname;
    bool        isnull;
 
    isnull = PG_ARGISNULL(0);
 
    if (!isnull)
    {
        tspname = PG_GETARG_NAME(0);
        tsid = get_tablespace_oid(NameStr(*tspname), false);
    }
 
    return pg_get_tablespace_ddl_srf(fcinfo, tsid, isnull);
}
 
/*
 * pg_get_database_ddl_internal
 *      Generate DDL statements to recreate a database.
 *
 * Returns a List of palloc'd strings.  The first element is the
 * CREATE DATABASE statement; subsequent elements are ALTER DATABASE
 * statements for properties and configuration settings.
 */
static List *
pg_get_database_ddl_internal(Oid dbid, bool pretty,
                             bool no_owner, bool no_tablespace)
{
    HeapTuple   tuple;
    Form_pg_database dbform;
    StringInfoData buf;
    bool        isnull;
    Datum       datum;
    const char *encoding;
    char       *dbname;
    char       *collate;
    char       *ctype;
    Relation    rel;
    ScanKeyData scankey[2];
    SysScanDesc scan;
    List       *statements = NIL;
    AclResult   aclresult;
 
    tuple = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(dbid));
    if (!HeapTupleIsValid(tuple))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("database with OID %u does not exist", dbid)));
 
    /* User must have connect privilege for target database. */
    aclresult = object_aclcheck(DatabaseRelationId, dbid, GetUserId(), ACL_CONNECT);
    if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, OBJECT_DATABASE,
                       get_database_name(dbid));
 
    dbform = (Form_pg_database) GETSTRUCT(tuple);
    dbname = pstrdup(NameStr(dbform->datname));
 
    /*
     * We don't support generating DDL for system databases.  The primary
     * reason for this is that users shouldn't be recreating them.
     */
    if (strcmp(dbname, "template0") == 0 || strcmp(dbname, "template1") == 0)
        ereport(ERROR,
                (errcode(ERRCODE_RESERVED_NAME),
                 errmsg("database \"%s\" is a system database", dbname),
                 errdetail("DDL generation is not supported for template0 and template1.")));
 
    initStringInfo(&buf);
 
    /* --- Build CREATE DATABASE statement --- */
    appendStringInfo(&buf, "CREATE DATABASE %s", quote_identifier(dbname));
 
    /*
     * Always use template0: the target database already contains the catalog
     * data from whatever template was used originally, so we must start from
     * the pristine template to avoid duplication.
     */
    append_ddl_option(&buf, pretty, 4, "WITH TEMPLATE = template0");
 
    /* ENCODING */
    encoding = pg_encoding_to_char(dbform->encoding);
    if (strlen(encoding) > 0)
        append_ddl_option(&buf, pretty, 4, "ENCODING = %s",
                          quote_literal_cstr(encoding));
 
    /* LOCALE_PROVIDER */
    if (dbform->datlocprovider == COLLPROVIDER_BUILTIN ||
        dbform->datlocprovider == COLLPROVIDER_ICU ||
        dbform->datlocprovider == COLLPROVIDER_LIBC)
        append_ddl_option(&buf, pretty, 4, "LOCALE_PROVIDER = %s",
                          collprovider_name(dbform->datlocprovider));
    else
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                 errmsg("unrecognized locale provider: %c",
                        dbform->datlocprovider)));
 
    /* LOCALE, LC_COLLATE, LC_CTYPE */
    datum = SysCacheGetAttr(DATABASEOID, tuple,
                            Anum_pg_database_datcollate, &isnull);
    collate = isnull ? NULL : TextDatumGetCString(datum);
    datum = SysCacheGetAttr(DATABASEOID, tuple,
                            Anum_pg_database_datctype, &isnull);
    ctype = isnull ? NULL : TextDatumGetCString(datum);
    if (collate != NULL && ctype != NULL && strcmp(collate, ctype) == 0)
    {
        append_ddl_option(&buf, pretty, 4, "LOCALE = %s",
                          quote_literal_cstr(collate));
    }
    else
    {
        if (collate != NULL)
            append_ddl_option(&buf, pretty, 4, "LC_COLLATE = %s",
                              quote_literal_cstr(collate));
        if (ctype != NULL)
            append_ddl_option(&buf, pretty, 4, "LC_CTYPE = %s",
                              quote_literal_cstr(ctype));
    }
 
    /* LOCALE (provider-specific) */
    datum = SysCacheGetAttr(DATABASEOID, tuple,
                            Anum_pg_database_datlocale, &isnull);
    if (!isnull)
    {
        const char *locale = TextDatumGetCString(datum);
 
        if (dbform->datlocprovider == COLLPROVIDER_BUILTIN)
            append_ddl_option(&buf, pretty, 4, "BUILTIN_LOCALE = %s",
                              quote_literal_cstr(locale));
        else if (dbform->datlocprovider == COLLPROVIDER_ICU)
            append_ddl_option(&buf, pretty, 4, "ICU_LOCALE = %s",
                              quote_literal_cstr(locale));
    }
 
    /* ICU_RULES */
    datum = SysCacheGetAttr(DATABASEOID, tuple,
                            Anum_pg_database_daticurules, &isnull);
    if (!isnull && dbform->datlocprovider == COLLPROVIDER_ICU)
        append_ddl_option(&buf, pretty, 4, "ICU_RULES = %s",
                          quote_literal_cstr(TextDatumGetCString(datum)));
 
    /* TABLESPACE */
    if (!no_tablespace && OidIsValid(dbform->dattablespace))
    {
        char       *spcname = get_tablespace_name(dbform->dattablespace);
 
        if (pg_strcasecmp(spcname, "pg_default") != 0)
            append_ddl_option(&buf, pretty, 4, "TABLESPACE = %s",
                              quote_identifier(spcname));
    }
 
    appendStringInfoChar(&buf, ';');
    statements = lappend(statements, pstrdup(buf.data));
 
    /* OWNER */
    if (!no_owner && OidIsValid(dbform->datdba))
    {
        char       *owner = GetUserNameFromId(dbform->datdba, false);
 
        resetStringInfo(&buf);
        appendStringInfo(&buf, "ALTER DATABASE %s OWNER TO %s;",
                         quote_identifier(dbname), quote_identifier(owner));
        pfree(owner);
        statements = lappend(statements, pstrdup(buf.data));
    }
 
    /* CONNECTION LIMIT */
    if (dbform->datconnlimit != -1)
    {
        resetStringInfo(&buf);
        appendStringInfo(&buf, "ALTER DATABASE %s CONNECTION LIMIT = %d;",
                         quote_identifier(dbname), dbform->datconnlimit);
        statements = lappend(statements, pstrdup(buf.data));
    }
 
    /* IS_TEMPLATE */
    if (dbform->datistemplate)
    {
        resetStringInfo(&buf);
        appendStringInfo(&buf, "ALTER DATABASE %s IS_TEMPLATE = true;",
                         quote_identifier(dbname));
        statements = lappend(statements, pstrdup(buf.data));
    }
 
    /* ALLOW_CONNECTIONS */
    if (!dbform->datallowconn)
    {
        resetStringInfo(&buf);
        appendStringInfo(&buf, "ALTER DATABASE %s ALLOW_CONNECTIONS = false;",
                         quote_identifier(dbname));
        statements = lappend(statements, pstrdup(buf.data));
    }
 
    ReleaseSysCache(tuple);
 
    /*
     * Now scan pg_db_role_setting for ALTER DATABASE SET configurations.
     *
     * It is only database-wide (setrole = 0). It generates one ALTER
     * statement per setting.
     */
    rel = table_open(DbRoleSettingRelationId, AccessShareLock);
    ScanKeyInit(&scankey[0],
                Anum_pg_db_role_setting_setdatabase,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(dbid));
    ScanKeyInit(&scankey[1],
                Anum_pg_db_role_setting_setrole,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(InvalidOid));
 
    scan = systable_beginscan(rel, DbRoleSettingDatidRolidIndexId, true,
                              NULL, 2, scankey);
 
    while (HeapTupleIsValid(tuple = systable_getnext(scan)))
    {
        ArrayType  *dbconfig;
        Datum      *settings;
        bool       *nulls;
        int         nsettings;
 
        /*
         * The setconfig column is a text array in "name=value" format. It
         * should never be null for a valid row, but be defensive.
         */
        datum = heap_getattr(tuple, Anum_pg_db_role_setting_setconfig,
                             RelationGetDescr(rel), &isnull);
        if (isnull)
            continue;
 
        dbconfig = DatumGetArrayTypeP(datum);
 
        deconstruct_array_builtin(dbconfig, TEXTOID, &settings, &nulls, &nsettings);
 
        for (int i = 0; i < nsettings; i++)
        {
            char       *s,
                       *p;
 
            if (nulls[i])
                continue;
 
            s = TextDatumGetCString(settings[i]);
            p = strchr(s, '=');
            if (p == NULL)
            {
                pfree(s);
                continue;
            }
            *p++ = '\0';
 
            resetStringInfo(&buf);
            appendStringInfo(&buf, "ALTER DATABASE %s SET %s TO ",
                             quote_identifier(dbname),
                             quote_identifier(s));
 
            append_guc_value(&buf, s, p);
 
            appendStringInfoChar(&buf, ';');
 
            statements = lappend(statements, pstrdup(buf.data));
 
            pfree(s);
        }
 
        pfree(settings);
        pfree(nulls);
        pfree(dbconfig);
    }
 
    systable_endscan(scan);
    table_close(rel, AccessShareLock);
 
    pfree(buf.data);
    pfree(dbname);
 
    return statements;
}
 
/*
 * pg_get_database_ddl
 *      Return DDL to recreate a database as a set of text rows.
 */
Datum
pg_get_database_ddl(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    List       *statements;
 
    if (SRF_IS_FIRSTCALL())
    {
        MemoryContext oldcontext;
        Oid         dbid;
        DdlOption   opts[] = {
            {"pretty", DDL_OPT_BOOL},
            {"owner", DDL_OPT_BOOL},
            {"tablespace", DDL_OPT_BOOL},
        };
 
        funcctx = SRF_FIRSTCALL_INIT();
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
        if (PG_ARGISNULL(0))
        {
            MemoryContextSwitchTo(oldcontext);
            SRF_RETURN_DONE(funcctx);
        }
 
        dbid = PG_GETARG_OID(0);
        parse_ddl_options(fcinfo, 1, opts, lengthof(opts));
 
        statements = pg_get_database_ddl_internal(dbid,
                                                  opts[0].isset && opts[0].boolval,
                                                  opts[1].isset && !opts[1].boolval,
                                                  opts[2].isset && !opts[2].boolval);
        funcctx->user_fctx = statements;
        funcctx->max_calls = list_length(statements);
 
        MemoryContextSwitchTo(oldcontext);
    }
 
    funcctx = SRF_PERCALL_SETUP();
    statements = (List *) funcctx->user_fctx;
 
    if (funcctx->call_cntr < funcctx->max_calls)
    {
        char       *stmt;
 
        stmt = list_nth(statements, funcctx->call_cntr);
 
        SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(stmt));
    }
    else
    {
        list_free_deep(statements);
        SRF_RETURN_DONE(funcctx);
    }
}