vacuuming.c

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/*-------------------------------------------------------------------------
 * vacuuming.c
 *      Helper routines for vacuumdb
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/bin/scripts/vacuuming.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
#include "catalog/pg_attribute_d.h"
#include "catalog/pg_class_d.h"
#include "common/connect.h"
#include "common/logging.h"
#include "fe_utils/cancel.h"
#include "fe_utils/option_utils.h"
#include "fe_utils/parallel_slot.h"
#include "fe_utils/query_utils.h"
#include "fe_utils/string_utils.h"
#include "vacuuming.h"
 
 
static int  vacuum_one_database(ConnParams *cparams,
                                vacuumingOptions *vacopts,
                                int stage,
                                SimpleStringList *objects,
                                SimpleStringList **found_objs,
                                int concurrentCons,
                                const char *progname);
static int  vacuum_all_databases(ConnParams *cparams,
                                 vacuumingOptions *vacopts,
                                 SimpleStringList *objects,
                                 int concurrentCons,
                                 const char *progname);
static SimpleStringList *retrieve_objects(PGconn *conn,
                                          vacuumingOptions *vacopts,
                                          SimpleStringList *objects);
static void free_retrieved_objects(SimpleStringList *list);
static void prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
                                   vacuumingOptions *vacopts, const char *table);
static void run_vacuum_command(ParallelSlot *free_slot,
                               vacuumingOptions *vacopts, const char *sql,
                               const char *table);
 
/*
 * Executes vacuum/analyze as indicated.  Returns 0 if the plan is carried
 * to completion, or -1 in case of certain errors (which should hopefully
 * been already reported.)  Other errors are reported via pg_fatal().
 */
int
vacuuming_main(ConnParams *cparams, const char *dbname,
               const char *maintenance_db, vacuumingOptions *vacopts,
               SimpleStringList *objects,
               unsigned int tbl_count, int concurrentCons,
               const char *progname)
{
    setup_cancel_handler(NULL);
 
    /* Avoid opening extra connections. */
    if (tbl_count > 0 && (concurrentCons > tbl_count))
        concurrentCons = tbl_count;
 
    if (vacopts->objfilter & OBJFILTER_ALL_DBS)
    {
        cparams->dbname = maintenance_db;
 
        return vacuum_all_databases(cparams, vacopts,
                                    objects,
                                    concurrentCons,
                                    progname);
    }
    else
    {
        if (dbname == NULL)
        {
            if (getenv("PGDATABASE"))
                dbname = getenv("PGDATABASE");
            else if (getenv("PGUSER"))
                dbname = getenv("PGUSER");
            else
                dbname = get_user_name_or_exit(progname);
        }
 
        cparams->dbname = dbname;
 
        if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
        {
            SimpleStringList *found_objs = NULL;
 
            for (int stage = 0; stage < ANALYZE_NUM_STAGES; stage++)
            {
                int         ret;
 
                ret = vacuum_one_database(cparams, vacopts,
                                          stage,
                                          objects,
                                          vacopts->missing_stats_only ? &found_objs : NULL,
                                          concurrentCons,
                                          progname);
                if (ret != 0)
                {
                    free_retrieved_objects(found_objs);
                    return ret;
                }
            }
 
            free_retrieved_objects(found_objs);
            return EXIT_SUCCESS;
        }
        else
            return vacuum_one_database(cparams, vacopts,
                                       ANALYZE_NO_STAGE,
                                       objects, NULL,
                                       concurrentCons,
                                       progname);
    }
}
 
/*
 * vacuum_one_database
 *
 * Process tables in the given database.
 *
 * There are two ways to specify the list of objects to process:
 *
 * 1) The "found_objs" parameter is a double pointer to a fully qualified list
 *    of objects to process, as returned by a previous call to
 *    vacuum_one_database().
 *
 *     a) If both "found_objs" (the double pointer) and "*found_objs" (the
 *        once-dereferenced double pointer) are not NULL, this list takes
 *        priority, and anything specified in "objects" is ignored.
 *
 *     b) If "found_objs" (the double pointer) is not NULL but "*found_objs"
 *        (the once-dereferenced double pointer) _is_ NULL, the "objects"
 *        parameter takes priority, and the results of the catalog query
 *        described in (2) are stored in "found_objs".
 *
 *     c) If "found_objs" (the double pointer) is NULL, the "objects"
 *        parameter again takes priority, and the results of the catalog query
 *        are not saved.
 *
 * 2) The "objects" parameter is a user-specified list of objects to process.
 *    When (1b) or (1c) applies, this function performs a catalog query to
 *    retrieve a fully qualified list of objects to process, as described
 *    below.
 *
 *     a) If "objects" is not NULL, the catalog query gathers only the objects
 *        listed in "objects".
 *
 *     b) If "objects" is NULL, all tables in the database are gathered.
 *
 * Note that this function is only concerned with running exactly one stage
 * when in analyze-in-stages mode; caller must iterate on us if necessary.
 *
 * If concurrentCons is > 1, multiple connections are used to vacuum tables
 * in parallel.
 */
static int
vacuum_one_database(ConnParams *cparams,
                    vacuumingOptions *vacopts,
                    int stage,
                    SimpleStringList *objects,
                    SimpleStringList **found_objs,
                    int concurrentCons,
                    const char *progname)
{
    PQExpBufferData sql;
    PGconn     *conn;
    SimpleStringListCell *cell;
    ParallelSlotArray *sa;
    int         ntups = 0;
    const char *initcmd;
    SimpleStringList *retobjs = NULL;
    bool        free_retobjs = false;
    int         ret = EXIT_SUCCESS;
    const char *stage_commands[] = {
        "SET default_statistics_target=1; SET vacuum_cost_delay=0;",
        "SET default_statistics_target=10; RESET vacuum_cost_delay;",
        "RESET default_statistics_target;"
    };
    const char *stage_messages[] = {
        gettext_noop("Generating minimal optimizer statistics (1 target)"),
        gettext_noop("Generating medium optimizer statistics (10 targets)"),
        gettext_noop("Generating default (full) optimizer statistics")
    };
 
    Assert(stage == ANALYZE_NO_STAGE ||
           (stage >= 0 && stage < ANALYZE_NUM_STAGES));
 
    conn = connectDatabase(cparams, progname, vacopts->echo, false, true);
 
    if (vacopts->disable_page_skipping && PQserverVersion(conn) < 90600)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "disable-page-skipping", "9.6");
    }
 
    if (vacopts->no_index_cleanup && PQserverVersion(conn) < 120000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "no-index-cleanup", "12");
    }
 
    if (vacopts->force_index_cleanup && PQserverVersion(conn) < 120000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "force-index-cleanup", "12");
    }
 
    if (!vacopts->do_truncate && PQserverVersion(conn) < 120000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "no-truncate", "12");
    }
 
    if (!vacopts->process_main && PQserverVersion(conn) < 160000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "no-process-main", "16");
    }
 
    if (!vacopts->process_toast && PQserverVersion(conn) < 140000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "no-process-toast", "14");
    }
 
    if (vacopts->skip_locked && PQserverVersion(conn) < 120000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "skip-locked", "12");
    }
 
    if (vacopts->min_xid_age != 0 && PQserverVersion(conn) < 90600)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "--min-xid-age", "9.6");
    }
 
    if (vacopts->min_mxid_age != 0 && PQserverVersion(conn) < 90600)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "--min-mxid-age", "9.6");
    }
 
    if (vacopts->parallel_workers >= 0 && PQserverVersion(conn) < 130000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "--parallel", "13");
    }
 
    if (vacopts->buffer_usage_limit && PQserverVersion(conn) < 160000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "--buffer-usage-limit", "16");
    }
 
    if (vacopts->missing_stats_only && PQserverVersion(conn) < 150000)
    {
        PQfinish(conn);
        pg_fatal("cannot use the \"%s\" option on server versions older than PostgreSQL %s",
                 "--missing-stats-only", "15");
    }
 
    /* skip_database_stats is used automatically if server supports it */
    vacopts->skip_database_stats = (PQserverVersion(conn) >= 160000);
 
    if (!vacopts->quiet)
    {
        if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
            printf(_("%s: processing database \"%s\": %s\n"),
                   progname, PQdb(conn), _(stage_messages[stage]));
        else
            printf(_("%s: vacuuming database \"%s\"\n"),
                   progname, PQdb(conn));
        fflush(stdout);
    }
 
    /*
     * If the caller provided the results of a previous catalog query, just
     * use that.  Otherwise, run the catalog query ourselves and set the
     * return variable if provided.  (If it is, then freeing the string list
     * becomes the caller's responsibility.)
     */
    if (found_objs && *found_objs)
        retobjs = *found_objs;
    else
    {
        retobjs = retrieve_objects(conn, vacopts, objects);
        if (found_objs)
            *found_objs = retobjs;
        else
            free_retobjs = true;
    }
 
    /*
     * Count the number of objects in the catalog query result.  If there are
     * none, we are done.
     */
    for (cell = retobjs->head; cell; cell = cell->next)
        ntups++;
 
    if (ntups == 0)
    {
        PQfinish(conn);
        if (free_retobjs)
            free_retrieved_objects(retobjs);
        return EXIT_SUCCESS;
    }
 
    /*
     * Ensure concurrentCons is sane.  If there are more connections than
     * vacuumable relations, we don't need to use them all.
     */
    if (concurrentCons > ntups)
        concurrentCons = ntups;
    if (concurrentCons <= 0)
        concurrentCons = 1;
 
    /*
     * All slots need to be prepared to run the appropriate analyze stage, if
     * caller requested that mode.  We have to prepare the initial connection
     * ourselves before setting up the slots.
     */
    if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
    {
        initcmd = stage_commands[stage];
 
        if (vacopts->dry_run)
            printf("%s\n", initcmd);
        else
            executeCommand(conn, initcmd, vacopts->echo);
    }
    else
        initcmd = NULL;
 
    /*
     * Setup the database connections. We reuse the connection we already have
     * for the first slot.  If not in parallel mode, the first slot in the
     * array contains the connection.
     */
    sa = ParallelSlotsSetup(concurrentCons, cparams, progname,
                            vacopts->echo, initcmd);
    ParallelSlotsAdoptConn(sa, conn);
 
    initPQExpBuffer(&sql);
 
    cell = retobjs->head;
    do
    {
        const char *tabname = cell->val;
        ParallelSlot *free_slot;
 
        if (CancelRequested)
        {
            ret = EXIT_FAILURE;
            goto finish;
        }
 
        free_slot = ParallelSlotsGetIdle(sa, NULL);
        if (!free_slot)
        {
            ret = EXIT_FAILURE;
            goto finish;
        }
 
        prepare_vacuum_command(free_slot->connection, &sql,
                               vacopts, tabname);
 
        /*
         * Execute the vacuum.  All errors are handled in processQueryResult
         * through ParallelSlotsGetIdle.
         */
        ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
        run_vacuum_command(free_slot, vacopts, sql.data, tabname);
 
        cell = cell->next;
    } while (cell != NULL);
 
    if (!ParallelSlotsWaitCompletion(sa))
    {
        ret = EXIT_FAILURE;
        goto finish;
    }
 
    /* If we used SKIP_DATABASE_STATS, mop up with ONLY_DATABASE_STATS */
    if (vacopts->mode == MODE_VACUUM && vacopts->skip_database_stats)
    {
        const char *cmd = "VACUUM (ONLY_DATABASE_STATS);";
        ParallelSlot *free_slot = ParallelSlotsGetIdle(sa, NULL);
 
        if (!free_slot)
        {
            ret = EXIT_FAILURE;
            goto finish;
        }
 
        ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
        run_vacuum_command(free_slot, vacopts, cmd, NULL);
 
        if (!ParallelSlotsWaitCompletion(sa))
            ret = EXIT_FAILURE; /* error already reported by handler */
    }
 
finish:
    ParallelSlotsTerminate(sa);
    pg_free(sa);
    termPQExpBuffer(&sql);
    if (free_retobjs)
        free_retrieved_objects(retobjs);
 
    return ret;
}
 
/*
 * Vacuum/analyze all connectable databases.
 *
 * In analyze-in-stages mode, we process all databases in one stage before
 * moving on to the next stage.  That ensure minimal stats are available
 * quickly everywhere before generating more detailed ones.
 */
static int
vacuum_all_databases(ConnParams *cparams,
                     vacuumingOptions *vacopts,
                     SimpleStringList *objects,
                     int concurrentCons,
                     const char *progname)
{
    int         ret = EXIT_SUCCESS;
    PGconn     *conn;
    PGresult   *result;
    int         numdbs;
 
    conn = connectMaintenanceDatabase(cparams, progname, vacopts->echo);
    result = executeQuery(conn,
                          "SELECT datname FROM pg_database WHERE datallowconn AND datconnlimit <> -2 ORDER BY 1;",
                          vacopts->echo);
    numdbs = PQntuples(result);
    PQfinish(conn);
 
    if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
    {
        SimpleStringList **found_objs = NULL;
 
        if (vacopts->missing_stats_only)
            found_objs = palloc0(numdbs * sizeof(SimpleStringList *));
 
        /*
         * When analyzing all databases in stages, we analyze them all in the
         * fastest stage first, so that initial statistics become available
         * for all of them as soon as possible.
         *
         * This means we establish several times as many connections, but
         * that's a secondary consideration.
         */
        for (int stage = 0; stage < ANALYZE_NUM_STAGES; stage++)
        {
            for (int i = 0; i < numdbs; i++)
            {
                cparams->override_dbname = PQgetvalue(result, i, 0);
                ret = vacuum_one_database(cparams, vacopts, stage,
                                          objects,
                                          vacopts->missing_stats_only ? &found_objs[i] : NULL,
                                          concurrentCons,
                                          progname);
                if (ret != EXIT_SUCCESS)
                    break;
            }
            if (ret != EXIT_SUCCESS)
                break;
        }
 
        if (vacopts->missing_stats_only)
        {
            for (int i = 0; i < numdbs; i++)
                free_retrieved_objects(found_objs[i]);
            pg_free(found_objs);
        }
    }
    else
    {
        for (int i = 0; i < numdbs; i++)
        {
            cparams->override_dbname = PQgetvalue(result, i, 0);
            ret = vacuum_one_database(cparams, vacopts,
                                      ANALYZE_NO_STAGE,
                                      objects,
                                      NULL,
                                      concurrentCons,
                                      progname);
            if (ret != EXIT_SUCCESS)
                break;
        }
    }
 
    PQclear(result);
 
    return ret;
}
 
/*
 * Prepare the list of tables to process by querying the catalogs.
 *
 * Since we execute the constructed query with the default search_path (which
 * could be unsafe), everything in this query MUST be fully qualified.
 *
 * First, build a WITH clause for the catalog query if any tables were
 * specified, with a set of values made of relation names and their optional
 * set of columns.  This is used to match any provided column lists with the
 * generated qualified identifiers and to filter for the tables provided via
 * --table.  If a listed table does not exist, the catalog query will fail.
 */
static SimpleStringList *
retrieve_objects(PGconn *conn, vacuumingOptions *vacopts,
                 SimpleStringList *objects)
{
    PQExpBufferData buf;
    PQExpBufferData catalog_query;
    PGresult   *res;
    SimpleStringListCell *cell;
    SimpleStringList *found_objs = palloc0_object(SimpleStringList);
    bool        objects_listed = false;
 
    initPQExpBuffer(&catalog_query);
    for (cell = objects ? objects->head : NULL; cell; cell = cell->next)
    {
        char       *just_table = NULL;
        const char *just_columns = NULL;
 
        if (!objects_listed)
        {
            appendPQExpBufferStr(&catalog_query,
                                 "WITH listed_objects (object_oid, column_list) AS (\n"
                                 "  VALUES (");
            objects_listed = true;
        }
        else
            appendPQExpBufferStr(&catalog_query, ",\n  (");
 
        if (vacopts->objfilter & (OBJFILTER_SCHEMA | OBJFILTER_SCHEMA_EXCLUDE))
        {
            appendStringLiteralConn(&catalog_query, cell->val, conn);
            appendPQExpBufferStr(&catalog_query, "::pg_catalog.regnamespace, ");
        }
 
        if (vacopts->objfilter & OBJFILTER_TABLE)
        {
            /*
             * Split relation and column names given by the user, this is used
             * to feed the CTE with values on which are performed pre-run
             * validity checks as well.  For now these happen only on the
             * relation name.
             */
            splitTableColumnsSpec(cell->val, PQclientEncoding(conn),
                                  &just_table, &just_columns);
 
            appendStringLiteralConn(&catalog_query, just_table, conn);
            appendPQExpBufferStr(&catalog_query, "::pg_catalog.regclass, ");
        }
 
        if (just_columns && just_columns[0] != '\0')
            appendStringLiteralConn(&catalog_query, just_columns, conn);
        else
            appendPQExpBufferStr(&catalog_query, "NULL");
 
        appendPQExpBufferStr(&catalog_query, "::pg_catalog.text)");
 
        pg_free(just_table);
    }
 
    /* Finish formatting the CTE */
    if (objects_listed)
        appendPQExpBufferStr(&catalog_query, "\n)\n");
 
    appendPQExpBufferStr(&catalog_query, "SELECT c.relname, ns.nspname");
 
    if (objects_listed)
        appendPQExpBufferStr(&catalog_query, ", listed_objects.column_list");
 
    appendPQExpBufferStr(&catalog_query,
                         " FROM pg_catalog.pg_class c\n"
                         " JOIN pg_catalog.pg_namespace ns"
                         " ON c.relnamespace OPERATOR(pg_catalog.=) ns.oid\n"
                         " CROSS JOIN LATERAL (SELECT c.relkind IN ("
                         CppAsString2(RELKIND_PARTITIONED_TABLE) ", "
                         CppAsString2(RELKIND_PARTITIONED_INDEX) ")) as p (inherited)\n"
                         " LEFT JOIN pg_catalog.pg_class t"
                         " ON c.reltoastrelid OPERATOR(pg_catalog.=) t.oid\n");
 
    /*
     * Used to match the tables or schemas listed by the user, completing the
     * JOIN clause.
     */
    if (objects_listed)
    {
        appendPQExpBufferStr(&catalog_query, " LEFT JOIN listed_objects"
                             " ON listed_objects.object_oid"
                             " OPERATOR(pg_catalog.=) ");
 
        if (vacopts->objfilter & OBJFILTER_TABLE)
            appendPQExpBufferStr(&catalog_query, "c.oid\n");
        else
            appendPQExpBufferStr(&catalog_query, "ns.oid\n");
    }
 
    /*
     * Exclude temporary tables, beginning the WHERE clause.
     */
    appendPQExpBufferStr(&catalog_query,
                         " WHERE c.relpersistence OPERATOR(pg_catalog.!=) "
                         CppAsString2(RELPERSISTENCE_TEMP) "\n");
 
    /*
     * Used to match the tables or schemas listed by the user, for the WHERE
     * clause.
     */
    if (objects_listed)
    {
        if (vacopts->objfilter & OBJFILTER_SCHEMA_EXCLUDE)
            appendPQExpBufferStr(&catalog_query,
                                 " AND listed_objects.object_oid IS NULL\n");
        else
            appendPQExpBufferStr(&catalog_query,
                                 " AND listed_objects.object_oid IS NOT NULL\n");
    }
 
    /*
     * If no tables were listed, filter for the relevant relation types.  If
     * tables were given via --table, don't bother filtering by relation type.
     * Instead, let the server decide whether a given relation can be
     * processed in which case the user will know about it.
     */
    if ((vacopts->objfilter & OBJFILTER_TABLE) == 0)
    {
        /*
         * vacuumdb should generally follow the behavior of the underlying
         * VACUUM and ANALYZE commands.  In MODE_ANALYZE or
         * MODE_ANALYZE_IN_STAGES modes, process regular tables, materialized
         * views, and partitioned tables, just like ANALYZE (with no specific
         * target tables) does. Otherwise, process only regular tables and
         * materialized views, since VACUUM skips partitioned tables when no
         * target tables are specified.
         */
        if (vacopts->mode == MODE_ANALYZE ||
            vacopts->mode == MODE_ANALYZE_IN_STAGES)
            appendPQExpBufferStr(&catalog_query,
                                 " AND c.relkind OPERATOR(pg_catalog.=) ANY (array["
                                 CppAsString2(RELKIND_RELATION) ", "
                                 CppAsString2(RELKIND_MATVIEW) ", "
                                 CppAsString2(RELKIND_PARTITIONED_TABLE) "])\n");
        else
            appendPQExpBufferStr(&catalog_query,
                                 " AND c.relkind OPERATOR(pg_catalog.=) ANY (array["
                                 CppAsString2(RELKIND_RELATION) ", "
                                 CppAsString2(RELKIND_MATVIEW) "])\n");
    }
 
    /*
     * For --min-xid-age and --min-mxid-age, the age of the relation is the
     * greatest of the ages of the main relation and its associated TOAST
     * table.  The commands generated by vacuumdb will also process the TOAST
     * table for the relation if necessary, so it does not need to be
     * considered separately.
     */
    if (vacopts->min_xid_age != 0)
    {
        appendPQExpBuffer(&catalog_query,
                          " AND GREATEST(pg_catalog.age(c.relfrozenxid),"
                          " pg_catalog.age(t.relfrozenxid)) "
                          " OPERATOR(pg_catalog.>=) '%d'::pg_catalog.int4\n"
                          " AND c.relfrozenxid OPERATOR(pg_catalog.!=)"
                          " '0'::pg_catalog.xid\n",
                          vacopts->min_xid_age);
    }
 
    if (vacopts->min_mxid_age != 0)
    {
        appendPQExpBuffer(&catalog_query,
                          " AND GREATEST(pg_catalog.mxid_age(c.relminmxid),"
                          " pg_catalog.mxid_age(t.relminmxid)) OPERATOR(pg_catalog.>=)"
                          " '%d'::pg_catalog.int4\n"
                          " AND c.relminmxid OPERATOR(pg_catalog.!=)"
                          " '0'::pg_catalog.xid\n",
                          vacopts->min_mxid_age);
    }
 
    if (vacopts->missing_stats_only)
    {
        appendPQExpBufferStr(&catalog_query, " AND (\n");
 
        /* regular stats */
        appendPQExpBufferStr(&catalog_query,
                             " EXISTS (SELECT NULL FROM pg_catalog.pg_attribute a\n"
                             " WHERE a.attrelid OPERATOR(pg_catalog.=) c.oid\n"
                             " AND a.attnum OPERATOR(pg_catalog.>) 0::pg_catalog.int2\n"
                             " AND NOT a.attisdropped\n"
                             " AND a.attstattarget IS DISTINCT FROM 0::pg_catalog.int2\n"
                             " AND a.attgenerated OPERATOR(pg_catalog.<>) "
                             CppAsString2(ATTRIBUTE_GENERATED_VIRTUAL) "\n"
                             " AND NOT EXISTS (SELECT NULL FROM pg_catalog.pg_statistic s\n"
                             " WHERE s.starelid OPERATOR(pg_catalog.=) a.attrelid\n"
                             " AND s.staattnum OPERATOR(pg_catalog.=) a.attnum\n"
                             " AND s.stainherit OPERATOR(pg_catalog.=) p.inherited))\n");
 
        /* extended stats */
        appendPQExpBufferStr(&catalog_query,
                             " OR EXISTS (SELECT NULL FROM pg_catalog.pg_statistic_ext e\n"
                             " WHERE e.stxrelid OPERATOR(pg_catalog.=) c.oid\n"
                             " AND e.stxstattarget IS DISTINCT FROM 0::pg_catalog.int2\n"
                             " AND NOT EXISTS (SELECT NULL FROM pg_catalog.pg_statistic_ext_data d\n"
                             " WHERE d.stxoid OPERATOR(pg_catalog.=) e.oid\n"
                             " AND d.stxdinherit OPERATOR(pg_catalog.=) p.inherited))\n");
 
        /* expression indexes */
        appendPQExpBufferStr(&catalog_query,
                             " OR EXISTS (SELECT NULL FROM pg_catalog.pg_attribute a\n"
                             " JOIN pg_catalog.pg_index i"
                             " ON i.indexrelid OPERATOR(pg_catalog.=) a.attrelid\n"
                             " WHERE i.indrelid OPERATOR(pg_catalog.=) c.oid\n"
                             " AND i.indkey[a.attnum OPERATOR(pg_catalog.-) 1::pg_catalog.int2]"
                             " OPERATOR(pg_catalog.=) 0::pg_catalog.int2\n"
                             " AND a.attnum OPERATOR(pg_catalog.>) 0::pg_catalog.int2\n"
                             " AND NOT a.attisdropped\n"
                             " AND a.attstattarget IS DISTINCT FROM 0::pg_catalog.int2\n"
                             " AND NOT EXISTS (SELECT NULL FROM pg_catalog.pg_statistic s\n"
                             " WHERE s.starelid OPERATOR(pg_catalog.=) a.attrelid\n"
                             " AND s.staattnum OPERATOR(pg_catalog.=) a.attnum\n"
                             " AND s.stainherit OPERATOR(pg_catalog.=) p.inherited))\n");
 
        /* inheritance and regular stats */
        appendPQExpBufferStr(&catalog_query,
                             " OR EXISTS (SELECT NULL FROM pg_catalog.pg_attribute a\n"
                             " WHERE a.attrelid OPERATOR(pg_catalog.=) c.oid\n"
                             " AND a.attnum OPERATOR(pg_catalog.>) 0::pg_catalog.int2\n"
                             " AND NOT a.attisdropped\n"
                             " AND a.attstattarget IS DISTINCT FROM 0::pg_catalog.int2\n"
                             " AND a.attgenerated OPERATOR(pg_catalog.<>) "
                             CppAsString2(ATTRIBUTE_GENERATED_VIRTUAL) "\n"
                             " AND c.relhassubclass\n"
                             " AND NOT p.inherited\n"
                             " AND EXISTS (SELECT NULL FROM pg_catalog.pg_inherits h\n"
                             " WHERE h.inhparent OPERATOR(pg_catalog.=) c.oid)\n"
                             " AND NOT EXISTS (SELECT NULL FROM pg_catalog.pg_statistic s\n"
                             " WHERE s.starelid OPERATOR(pg_catalog.=) a.attrelid\n"
                             " AND s.staattnum OPERATOR(pg_catalog.=) a.attnum\n"
                             " AND s.stainherit))\n");
 
        /* inheritance and extended stats */
        appendPQExpBufferStr(&catalog_query,
                             " OR EXISTS (SELECT NULL FROM pg_catalog.pg_statistic_ext e\n"
                             " WHERE e.stxrelid OPERATOR(pg_catalog.=) c.oid\n"
                             " AND e.stxstattarget IS DISTINCT FROM 0::pg_catalog.int2\n"
                             " AND c.relhassubclass\n"
                             " AND NOT p.inherited\n"
                             " AND EXISTS (SELECT NULL FROM pg_catalog.pg_inherits h\n"
                             " WHERE h.inhparent OPERATOR(pg_catalog.=) c.oid)\n"
                             " AND NOT EXISTS (SELECT NULL FROM pg_catalog.pg_statistic_ext_data d\n"
                             " WHERE d.stxoid OPERATOR(pg_catalog.=) e.oid\n"
                             " AND d.stxdinherit))\n");
 
        appendPQExpBufferStr(&catalog_query, " )\n");
    }
 
    /*
     * Execute the catalog query.  We use the default search_path for this
     * query for consistency with table lookups done elsewhere by the user.
     */
    appendPQExpBufferStr(&catalog_query, " ORDER BY c.relpages DESC;");
    executeCommand(conn, "RESET search_path;", vacopts->echo);
    res = executeQuery(conn, catalog_query.data, vacopts->echo);
    termPQExpBuffer(&catalog_query);
    PQclear(executeQuery(conn, ALWAYS_SECURE_SEARCH_PATH_SQL, vacopts->echo));
 
    /*
     * Build qualified identifiers for each table, including the column list
     * if given.
     */
    initPQExpBuffer(&buf);
    for (int i = 0; i < PQntuples(res); i++)
    {
        appendPQExpBufferStr(&buf,
                             fmtQualifiedIdEnc(PQgetvalue(res, i, 1),
                                               PQgetvalue(res, i, 0),
                                               PQclientEncoding(conn)));
 
        if (objects_listed && !PQgetisnull(res, i, 2))
            appendPQExpBufferStr(&buf, PQgetvalue(res, i, 2));
 
        simple_string_list_append(found_objs, buf.data);
        resetPQExpBuffer(&buf);
    }
    termPQExpBuffer(&buf);
    PQclear(res);
 
    return found_objs;
}
 
/*
 * Free the results of retrieve_objects().
 *
 * For caller convenience, we allow the argument to be NULL,
 * although retrieve_objects() will never return that.
 */
static void
free_retrieved_objects(SimpleStringList *list)
{
    if (list)
    {
        simple_string_list_destroy(list);
        pg_free(list);
    }
}
 
/*
 * Construct a vacuum/analyze command to run based on the given
 * options, in the given string buffer, which may contain previous garbage.
 *
 * The table name used must be already properly quoted.  The command generated
 * depends on the server version involved and it is semicolon-terminated.
 */
static void
prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
                       vacuumingOptions *vacopts, const char *table)
{
    int         serverVersion = PQserverVersion(conn);
    const char *paren = " (";
    const char *comma = ", ";
    const char *sep = paren;
 
    resetPQExpBuffer(sql);
 
    if (vacopts->mode == MODE_ANALYZE ||
        vacopts->mode == MODE_ANALYZE_IN_STAGES)
    {
        appendPQExpBufferStr(sql, "ANALYZE");
 
        /* parenthesized grammar of ANALYZE is supported since v11 */
        if (serverVersion >= 110000)
        {
            if (vacopts->skip_locked)
            {
                /* SKIP_LOCKED is supported since v12 */
                Assert(serverVersion >= 120000);
                appendPQExpBuffer(sql, "%sSKIP_LOCKED", sep);
                sep = comma;
            }
            if (vacopts->verbose)
            {
                appendPQExpBuffer(sql, "%sVERBOSE", sep);
                sep = comma;
            }
            if (vacopts->buffer_usage_limit)
            {
                Assert(serverVersion >= 160000);
                appendPQExpBuffer(sql, "%sBUFFER_USAGE_LIMIT '%s'", sep,
                                  vacopts->buffer_usage_limit);
                sep = comma;
            }
            if (sep != paren)
                appendPQExpBufferChar(sql, ')');
        }
        else
        {
            if (vacopts->verbose)
                appendPQExpBufferStr(sql, " VERBOSE");
        }
    }
    else
    {
        appendPQExpBufferStr(sql, "VACUUM");
 
        /* parenthesized grammar of VACUUM is supported since v9.0 */
        if (serverVersion >= 90000)
        {
            if (vacopts->disable_page_skipping)
            {
                /* DISABLE_PAGE_SKIPPING is supported since v9.6 */
                Assert(serverVersion >= 90600);
                appendPQExpBuffer(sql, "%sDISABLE_PAGE_SKIPPING", sep);
                sep = comma;
            }
            if (vacopts->no_index_cleanup)
            {
                /* "INDEX_CLEANUP FALSE" has been supported since v12 */
                Assert(serverVersion >= 120000);
                Assert(!vacopts->force_index_cleanup);
                appendPQExpBuffer(sql, "%sINDEX_CLEANUP FALSE", sep);
                sep = comma;
            }
            if (vacopts->force_index_cleanup)
            {
                /* "INDEX_CLEANUP TRUE" has been supported since v12 */
                Assert(serverVersion >= 120000);
                Assert(!vacopts->no_index_cleanup);
                appendPQExpBuffer(sql, "%sINDEX_CLEANUP TRUE", sep);
                sep = comma;
            }
            if (!vacopts->do_truncate)
            {
                /* TRUNCATE is supported since v12 */
                Assert(serverVersion >= 120000);
                appendPQExpBuffer(sql, "%sTRUNCATE FALSE", sep);
                sep = comma;
            }
            if (!vacopts->process_main)
            {
                /* PROCESS_MAIN is supported since v16 */
                Assert(serverVersion >= 160000);
                appendPQExpBuffer(sql, "%sPROCESS_MAIN FALSE", sep);
                sep = comma;
            }
            if (!vacopts->process_toast)
            {
                /* PROCESS_TOAST is supported since v14 */
                Assert(serverVersion >= 140000);
                appendPQExpBuffer(sql, "%sPROCESS_TOAST FALSE", sep);
                sep = comma;
            }
            if (vacopts->skip_database_stats)
            {
                /* SKIP_DATABASE_STATS is supported since v16 */
                Assert(serverVersion >= 160000);
                appendPQExpBuffer(sql, "%sSKIP_DATABASE_STATS", sep);
                sep = comma;
            }
            if (vacopts->skip_locked)
            {
                /* SKIP_LOCKED is supported since v12 */
                Assert(serverVersion >= 120000);
                appendPQExpBuffer(sql, "%sSKIP_LOCKED", sep);
                sep = comma;
            }
            if (vacopts->full)
            {
                appendPQExpBuffer(sql, "%sFULL", sep);
                sep = comma;
            }
            if (vacopts->freeze)
            {
                appendPQExpBuffer(sql, "%sFREEZE", sep);
                sep = comma;
            }
            if (vacopts->verbose)
            {
                appendPQExpBuffer(sql, "%sVERBOSE", sep);
                sep = comma;
            }
            if (vacopts->and_analyze)
            {
                appendPQExpBuffer(sql, "%sANALYZE", sep);
                sep = comma;
            }
            if (vacopts->parallel_workers >= 0)
            {
                /* PARALLEL is supported since v13 */
                Assert(serverVersion >= 130000);
                appendPQExpBuffer(sql, "%sPARALLEL %d", sep,
                                  vacopts->parallel_workers);
                sep = comma;
            }
            if (vacopts->buffer_usage_limit)
            {
                Assert(serverVersion >= 160000);
                appendPQExpBuffer(sql, "%sBUFFER_USAGE_LIMIT '%s'", sep,
                                  vacopts->buffer_usage_limit);
                sep = comma;
            }
            if (sep != paren)
                appendPQExpBufferChar(sql, ')');
        }
        else
        {
            if (vacopts->full)
                appendPQExpBufferStr(sql, " FULL");
            if (vacopts->freeze)
                appendPQExpBufferStr(sql, " FREEZE");
            if (vacopts->verbose)
                appendPQExpBufferStr(sql, " VERBOSE");
            if (vacopts->and_analyze)
                appendPQExpBufferStr(sql, " ANALYZE");
        }
    }
 
    appendPQExpBuffer(sql, " %s;", table);
}
 
/*
 * Send a vacuum/analyze command to the server, returning after sending the
 * command.  If dry_run is true, the command is printed but not sent to the
 * server.
 *
 * Any errors during command execution are reported to stderr.
 */
static void
run_vacuum_command(ParallelSlot *free_slot, vacuumingOptions *vacopts,
                   const char *sql, const char *table)
{
    bool        status = true;
    PGconn     *conn = free_slot->connection;
 
    if (vacopts->echo || vacopts->dry_run)
        printf("%s\n", sql);
 
    if (vacopts->dry_run)
        ParallelSlotSetIdle(free_slot);
    else
        status = PQsendQuery(conn, sql) == 1;
 
    if (!status)
    {
        if (table)
        {
            pg_log_error("vacuuming of table \"%s\" in database \"%s\" failed: %s",
                         table, PQdb(conn), PQerrorMessage(conn));
        }
        else
        {
            pg_log_error("vacuuming of database \"%s\" failed: %s",
                         PQdb(conn), PQerrorMessage(conn));
        }
    }
}
 
/*
 * Returns a newly malloc'd version of 'src' with escaped single quotes and
 * backslashes.
 */
char *
escape_quotes(const char *src)
{
    char       *result = escape_single_quotes_ascii(src);
 
    if (!result)
        pg_fatal("out of memory");
    return result;
}