pg_stash_advice.c File Reference

#include "postgres.h"
#include "common/hashfn.h"
#include "common/string.h"
#include "miscadmin.h"
#include "nodes/queryjumble.h"
#include "pg_plan_advice.h"
#include "pg_stash_advice.h"
#include "postmaster/bgworker.h"
#include "storage/dsm_registry.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "lib/simplehash.h"

Include dependency graph for pg_stash_advice.c:

Go to the source code of this file.

Macros
#define	SH_PREFIX   pgsa_stash_name_table
#define	SH_ELEMENT_TYPE   pgsa_stash_name
#define	SH_KEY_TYPE   uint64
#define	SH_KEY   pgsa_stash_id
#define	SH_HASH_KEY(tb, key)   hash_bytes((const unsigned char *) &(key), sizeof(uint64))
#define	SH_EQUAL(tb, a, b)   (a == b)
#define	SH_SCOPE   extern
#define	SH_DEFINE

Functions
static char *	pgsa_advisor (PlannerGlobal *glob, Query *parse, const char *query_string, int cursorOptions, ExplainState *es)
static bool	pgsa_check_stash_name_guc (char **newval, void **extra, GucSource source)
static void	pgsa_init_shared_state (void *ptr, void *arg)
static bool	pgsa_is_identifier (char *str)
void	_PG_init (void)
void	pgsa_attach (void)
void	pgsa_check_lockout (void)
void	pgsa_check_stash_name (char *stash_name)
void	pgsa_create_stash (char *stash_name)
void	pgsa_clear_advice_string (char *stash_name, int64 queryId)
void	pgsa_drop_stash (char *stash_name)
void	pgsa_reset_all_stashes (void)
uint64	pgsa_lookup_stash_id (char *stash_name)
void	pgsa_set_advice_string (char *stash_name, int64 queryId, char *advice_string)
void	pgsa_start_worker (void)

Variables
	PG_MODULE_MAGIC
static dshash_parameters	pgsa_stash_dshash_parameters
static dshash_parameters	pgsa_entry_dshash_parameters
static char *	pg_stash_advice_stash_name = ""
bool	pg_stash_advice_persist = true
int	pg_stash_advice_persist_interval = 30
pgsa_shared_state *	pgsa_state
dsa_area *	pgsa_dsa_area
dshash_table *	pgsa_stash_dshash
dshash_table *	pgsa_entry_dshash
static MemoryContext	pg_stash_advice_mcxt

Macro Definition Documentation

SH_DEFINE

#define SH_DEFINE

Definition at line 79 of file pg_stash_advice.c.

SH_ELEMENT_TYPE

#define SH_ELEMENT_TYPE   pgsa_stash_name

Definition at line 73 of file pg_stash_advice.c.

SH_EQUAL

#define SH_EQUAL	(		tb,
			a,
			b
	)		(a == b)

Definition at line 77 of file pg_stash_advice.c.

SH_HASH_KEY

#define SH_HASH_KEY	(		tb,
			key
	)		hash_bytes((const unsigned char *) &(key), sizeof(uint64))

Definition at line 76 of file pg_stash_advice.c.

SH_KEY

#define SH_KEY   pgsa_stash_id

Definition at line 75 of file pg_stash_advice.c.

SH_KEY_TYPE

#define SH_KEY_TYPE   uint64

Definition at line 74 of file pg_stash_advice.c.

SH_PREFIX

#define SH_PREFIX   pgsa_stash_name_table

Definition at line 72 of file pg_stash_advice.c.

SH_SCOPE

#define SH_SCOPE   extern

Definition at line 78 of file pg_stash_advice.c.

Function Documentation

_PG_init()

void _PG_init

(

void

)

Definition at line 86 of file pg_stash_advice.c.

{
    void        (*add_advisor_fn) (pg_plan_advice_advisor_hook hook);
 
    /* If compute_query_id = 'auto', we would like query IDs. */
    EnableQueryId();
 
    /* Define our GUCs. */
    if (process_shared_preload_libraries_in_progress)
        DefineCustomBoolVariable("pg_stash_advice.persist",
                                 "Save and restore advice stash contents across restarts.",
                                 NULL,
                                 &pg_stash_advice_persist,
                                 true,
                                 PGC_POSTMASTER,
                                 0,
                                 NULL,
                                 NULL,
                                 NULL);
    else
        pg_stash_advice_persist = false;
 
    DefineCustomIntVariable("pg_stash_advice.persist_interval",
                            "Interval between advice stash saves, in seconds.",
                            NULL,
                            &pg_stash_advice_persist_interval,
                            30,
                            0,
                            3600,
                            PGC_SIGHUP,
                            GUC_UNIT_S,
                            NULL,
                            NULL,
                            NULL);
 
    DefineCustomStringVariable("pg_stash_advice.stash_name",
                               "Name of the advice stash to be used in this session.",
                               NULL,
                               &pg_stash_advice_stash_name,
                               "",
                               PGC_USERSET,
                               0,
                               pgsa_check_stash_name_guc,
                               NULL,
                               NULL);
 
    MarkGUCPrefixReserved("pg_stash_advice");
 
    /* Start the background worker for persistence, if enabled. */
    if (pg_stash_advice_persist)
        pgsa_start_worker();
 
    /* Tell pg_plan_advice that we want to provide advice strings. */
    add_advisor_fn =
        load_external_function("pg_plan_advice", "pg_plan_advice_add_advisor",
                               true, NULL);
    (*add_advisor_fn) (pgsa_advisor);
}

References DefineCustomBoolVariable(), DefineCustomIntVariable(), DefineCustomStringVariable(), EnableQueryId(), fb(), GUC_UNIT_S, load_external_function(), MarkGUCPrefixReserved(), pg_stash_advice_persist, pg_stash_advice_persist_interval, pg_stash_advice_stash_name, PGC_POSTMASTER, PGC_SIGHUP, PGC_USERSET, pgsa_advisor(), pgsa_check_stash_name_guc(), pgsa_start_worker(), and process_shared_preload_libraries_in_progress.

pgsa_advisor()

static char * pgsa_advisor ( PlannerGlobal *  glob, Query *  parse, const char *  query_string, int  cursorOptions, ExplainState *  es  )

static

Definition at line 150 of file pg_stash_advice.c.

{
    pgsa_entry_key key;
    pgsa_entry *entry;
    char       *advice_string;
    uint64      stash_id;
 
    /*
     * Exit quickly if the stash name is empty or there's no query ID.
     */
    if (pg_stash_advice_stash_name[0] == '\0' || parse->queryId == 0)
        return NULL;
 
    /* Attach to dynamic shared memory if not already done. */
    if (unlikely(pgsa_entry_dshash == NULL))
        pgsa_attach();
 
    /* If stash data is still being restored from disk, ignore. */
    if (pg_atomic_unlocked_test_flag(&pgsa_state->stashes_ready))
        return NULL;
 
    /*
     * Translate pg_stash_advice.stash_name to an integer ID.
     *
     * pgsa_check_stash_name_guc() has already validated the advice stash
     * name, so we don't need to call pgsa_check_stash_name() here.
     */
    stash_id = pgsa_lookup_stash_id(pg_stash_advice_stash_name);
    if (stash_id == 0)
        return NULL;
 
    /*
     * Look up the advice string for the given stash ID + query ID.
     *
     * If we find an advice string, we copy it into the current memory
     * context, presumably short-lived, so that we can release the lock on the
     * dshash entry. pg_plan_advice only needs the value to remain allocated
     * long enough for it to be parsed, so this should be good enough.
     */
    memset(&key, 0, sizeof(pgsa_entry_key));
    key.pgsa_stash_id = stash_id;
    key.queryId = parse->queryId;
    entry = dshash_find(pgsa_entry_dshash, &key, false);
    if (entry == NULL)
        return NULL;
    if (entry->advice_string == InvalidDsaPointer)
        advice_string = NULL;
    else
        advice_string = pstrdup(dsa_get_address(pgsa_dsa_area,
                                                entry->advice_string));
    dshash_release_lock(pgsa_entry_dshash, entry);
 
    /* If we found an advice string, emit a debug message. */
    if (advice_string != NULL)
        elog(DEBUG2, "supplying automatic advice for stash \"%s\", query ID %" PRId64 ": %s",
             pg_stash_advice_stash_name, key.queryId, advice_string);
 
    return advice_string;
}

References pgsa_entry::advice_string, DEBUG2, dsa_get_address(), dshash_find(), dshash_release_lock(), elog, fb(), InvalidDsaPointer, parse(), pg_atomic_unlocked_test_flag(), pg_stash_advice_stash_name, pgsa_attach(), pgsa_dsa_area, pgsa_entry_dshash, pgsa_lookup_stash_id(), pgsa_state, pstrdup(), pgsa_shared_state::stashes_ready, and unlikely.

Referenced by _PG_init().

pgsa_attach()

void pgsa_attach

(

void

)

Definition at line 221 of file pg_stash_advice.c.

{
    bool        found;
    MemoryContext oldcontext;
 
    /*
     * Create a memory context to make sure that any control structures
     * allocated in local memory are sufficiently persistent.
     */
    if (pg_stash_advice_mcxt == NULL)
        pg_stash_advice_mcxt = AllocSetContextCreate(TopMemoryContext,
                                                     "pg_stash_advice",
                                                     ALLOCSET_DEFAULT_SIZES);
    oldcontext = MemoryContextSwitchTo(pg_stash_advice_mcxt);
 
    /* Attach to the fixed-size state object if not already done. */
    if (pgsa_state == NULL)
        pgsa_state = GetNamedDSMSegment("pg_stash_advice",
                                        sizeof(pgsa_shared_state),
                                        pgsa_init_shared_state,
                                        &found, NULL);
 
    /* Attach to the DSA area if not already done. */
    if (pgsa_dsa_area == NULL)
    {
        dsa_handle  area_handle;
 
        LWLockAcquire(&pgsa_state->lock, LW_EXCLUSIVE);
        area_handle = pgsa_state->area;
        if (area_handle == DSA_HANDLE_INVALID)
        {
            pgsa_dsa_area = dsa_create(pgsa_state->dsa_tranche);
            dsa_pin(pgsa_dsa_area);
            pgsa_state->area = dsa_get_handle(pgsa_dsa_area);
            LWLockRelease(&pgsa_state->lock);
        }
        else
        {
            LWLockRelease(&pgsa_state->lock);
            pgsa_dsa_area = dsa_attach(area_handle);
        }
        dsa_pin_mapping(pgsa_dsa_area);
    }
 
    /* Attach to the stash_name->stash_id hash table if not already done. */
    if (pgsa_stash_dshash == NULL)
    {
        dshash_table_handle stash_handle;
 
        LWLockAcquire(&pgsa_state->lock, LW_EXCLUSIVE);
        pgsa_stash_dshash_parameters.tranche_id = pgsa_state->stash_tranche;
        stash_handle = pgsa_state->stash_hash;
        if (stash_handle == DSHASH_HANDLE_INVALID)
        {
            pgsa_stash_dshash = dshash_create(pgsa_dsa_area,
                                              &pgsa_stash_dshash_parameters,
                                              NULL);
            pgsa_state->stash_hash =
                dshash_get_hash_table_handle(pgsa_stash_dshash);
            LWLockRelease(&pgsa_state->lock);
        }
        else
        {
            LWLockRelease(&pgsa_state->lock);
            pgsa_stash_dshash = dshash_attach(pgsa_dsa_area,
                                              &pgsa_stash_dshash_parameters,
                                              stash_handle, NULL);
        }
    }
 
    /* Attach to the entry hash table if not already done. */
    if (pgsa_entry_dshash == NULL)
    {
        dshash_table_handle entry_handle;
 
        LWLockAcquire(&pgsa_state->lock, LW_EXCLUSIVE);
        pgsa_entry_dshash_parameters.tranche_id = pgsa_state->entry_tranche;
        entry_handle = pgsa_state->entry_hash;
        if (entry_handle == DSHASH_HANDLE_INVALID)
        {
            pgsa_entry_dshash = dshash_create(pgsa_dsa_area,
                                              &pgsa_entry_dshash_parameters,
                                              NULL);
            pgsa_state->entry_hash =
                dshash_get_hash_table_handle(pgsa_entry_dshash);
            LWLockRelease(&pgsa_state->lock);
        }
        else
        {
            LWLockRelease(&pgsa_state->lock);
            pgsa_entry_dshash = dshash_attach(pgsa_dsa_area,
                                              &pgsa_entry_dshash_parameters,
                                              entry_handle, NULL);
        }
    }
 
    /* Restore previous memory context. */
    MemoryContextSwitchTo(oldcontext);
}

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, pgsa_shared_state::area, dsa_attach(), dsa_create, dsa_get_handle(), DSA_HANDLE_INVALID, dsa_pin(), dsa_pin_mapping(), pgsa_shared_state::dsa_tranche, dshash_attach(), dshash_create(), dshash_get_hash_table_handle(), DSHASH_HANDLE_INVALID, pgsa_shared_state::entry_hash, pgsa_shared_state::entry_tranche, fb(), GetNamedDSMSegment(), pgsa_shared_state::lock, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MemoryContextSwitchTo(), pg_stash_advice_mcxt, pgsa_dsa_area, pgsa_entry_dshash, pgsa_entry_dshash_parameters, pgsa_init_shared_state(), pgsa_stash_dshash, pgsa_stash_dshash_parameters, pgsa_state, pgsa_shared_state::stash_hash, pgsa_shared_state::stash_tranche, TopMemoryContext, and dshash_parameters::tranche_id.

Referenced by pg_create_advice_stash(), pg_drop_advice_stash(), pg_get_advice_stash_contents(), pg_get_advice_stashes(), pg_set_stashed_advice(), pg_start_stash_advice_worker(), pg_stash_advice_worker_main(), and pgsa_advisor().

pgsa_check_lockout()

void pgsa_check_lockout

(

void

)

Definition at line 325 of file pg_stash_advice.c.

{
    if (pg_atomic_unlocked_test_flag(&pgsa_state->stashes_ready))
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("stash modifications are not allowed because \"%s\" has not been loaded yet",
                        PGSA_DUMP_FILE)));
}

References ereport, errcode(), errmsg, ERROR, fb(), pg_atomic_unlocked_test_flag(), PGSA_DUMP_FILE, pgsa_state, and pgsa_shared_state::stashes_ready.

Referenced by pg_create_advice_stash(), pg_drop_advice_stash(), and pg_set_stashed_advice().

pgsa_check_stash_name()

void pgsa_check_stash_name

(

char *

stash_name

)

Definition at line 340 of file pg_stash_advice.c.

{
    /* Reject empty advice stash name. */
    if (stash_name[0] == '\0')
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash name may not be zero length"));
 
    /* Reject overlong advice stash names. */
    if (strlen(stash_name) + 1 > NAMEDATALEN)
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash names may not be longer than %d bytes",
                       NAMEDATALEN - 1));
 
    /*
     * Reject non-ASCII advice stash names, since advice stashes are visible
     * across all databases and the encodings of those databases might differ.
     */
    if (!pg_is_ascii(stash_name))
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash name must not contain non-ASCII characters"));
 
    /*
     * Reject things that do not look like identifiers, since the ability to
     * create an advice stash with non-printable characters or weird symbols
     * in the name is not likely to be useful to anyone.
     */
    if (!pgsa_is_identifier(stash_name))
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash name must begin with a letter or underscore and contain only letters, digits, and underscores"));
}

References ereport, errcode(), errmsg, ERROR, fb(), NAMEDATALEN, pg_is_ascii(), and pgsa_is_identifier().

Referenced by pg_create_advice_stash(), pg_drop_advice_stash(), pg_get_advice_stash_contents(), and pg_set_stashed_advice().

pgsa_check_stash_name_guc()

static bool pgsa_check_stash_name_guc ( char **  newval, void **  extra, GucSource  source  )

static

Definition at line 380 of file pg_stash_advice.c.

{
    char       *stash_name = *newval;
 
    /* Reject overlong advice stash names. */
    if (strlen(stash_name) + 1 > NAMEDATALEN)
    {
        GUC_check_errcode(ERRCODE_INVALID_PARAMETER_VALUE);
        GUC_check_errdetail("advice stash names may not be longer than %d bytes",
                            NAMEDATALEN - 1);
        return false;
    }
 
    /*
     * Reject non-ASCII advice stash names, since advice stashes are visible
     * across all databases and the encodings of those databases might differ.
     */
    if (!pg_is_ascii(stash_name))
    {
        GUC_check_errcode(ERRCODE_INVALID_PARAMETER_VALUE);
        GUC_check_errdetail("advice stash name must not contain non-ASCII characters");
        return false;
    }
 
    /*
     * Reject things that do not look like identifiers, since the ability to
     * create an advice stash with non-printable characters or weird symbols
     * in the name is not likely to be useful to anyone.
     */
    if (!pgsa_is_identifier(stash_name))
    {
        GUC_check_errcode(ERRCODE_INVALID_PARAMETER_VALUE);
        GUC_check_errdetail("advice stash name must begin with a letter or underscore and contain only letters, digits, and underscores");
        return false;
    }
 
    return true;
}

References fb(), GUC_check_errcode(), GUC_check_errdetail, NAMEDATALEN, newval, pg_is_ascii(), and pgsa_is_identifier().

Referenced by _PG_init().

pgsa_clear_advice_string()

void pgsa_clear_advice_string	(	char *	stash_name,
		int64	queryId
	)

Definition at line 447 of file pg_stash_advice.c.

{
    pgsa_entry *entry;
    pgsa_entry_key key;
    uint64      stash_id;
    dsa_pointer old_dp;
 
    Assert(LWLockHeldByMe(&pgsa_state->lock));
 
    /* Translate the stash name to an integer ID. */
    if ((stash_id = pgsa_lookup_stash_id(stash_name)) == 0)
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash \"%s\" does not exist", stash_name));
 
    /*
     * Look for an existing entry, and free it. But, be sure to save the
     * pointer to the associated advice string, if any.
     */
    memset(&key, 0, sizeof(pgsa_entry_key));
    key.pgsa_stash_id = stash_id;
    key.queryId = queryId;
    entry = dshash_find(pgsa_entry_dshash, &key, true);
    if (entry == NULL)
        old_dp = InvalidDsaPointer;
    else
    {
        old_dp = entry->advice_string;
        dshash_delete_entry(pgsa_entry_dshash, entry);
    }
 
    /* Now we free the advice string as well, if there was one. */
    if (old_dp != InvalidDsaPointer)
        dsa_free(pgsa_dsa_area, old_dp);
 
    /* Bump change count. */
    pg_atomic_add_fetch_u64(&pgsa_state->change_count, 1);
}

References pgsa_entry::advice_string, Assert, pgsa_shared_state::change_count, dsa_free(), dshash_delete_entry(), dshash_find(), ereport, errcode(), errmsg, ERROR, fb(), InvalidDsaPointer, pgsa_shared_state::lock, LWLockHeldByMe(), pg_atomic_add_fetch_u64(), pgsa_dsa_area, pgsa_entry_dshash, pgsa_lookup_stash_id(), and pgsa_state.

Referenced by pg_set_stashed_advice().

pgsa_create_stash()

void pgsa_create_stash

(

char *

stash_name

)

Definition at line 423 of file pg_stash_advice.c.

{
    pgsa_stash *stash;
    bool        found;
 
    Assert(LWLockHeldByMeInMode(&pgsa_state->lock, LW_EXCLUSIVE));
 
    /* Create a stash with this name, unless one already exists. */
    stash = dshash_find_or_insert(pgsa_stash_dshash, stash_name, &found);
    if (found)
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash \"%s\" already exists", stash_name));
    stash->pgsa_stash_id = pgsa_state->next_stash_id++;
    dshash_release_lock(pgsa_stash_dshash, stash);
 
    /* Bump change count. */
    pg_atomic_add_fetch_u64(&pgsa_state->change_count, 1);
}

References Assert, pgsa_shared_state::change_count, dshash_find_or_insert, dshash_release_lock(), ereport, errcode(), errmsg, ERROR, fb(), pgsa_shared_state::lock, LW_EXCLUSIVE, LWLockHeldByMeInMode(), pgsa_shared_state::next_stash_id, pg_atomic_add_fetch_u64(), pgsa_stash_dshash, and pgsa_state.

Referenced by pg_create_advice_stash(), and pgsa_restore_stashes().

pgsa_drop_stash()

void pgsa_drop_stash

(

char *

stash_name

)

Definition at line 490 of file pg_stash_advice.c.

{
    pgsa_entry *entry;
    pgsa_stash *stash;
    dshash_seq_status iterator;
    uint64      stash_id;
 
    Assert(LWLockHeldByMeInMode(&pgsa_state->lock, LW_EXCLUSIVE));
 
    /* Remove the entry for this advice stash. */
    stash = dshash_find(pgsa_stash_dshash, stash_name, true);
    if (stash == NULL)
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash \"%s\" does not exist", stash_name));
    stash_id = stash->pgsa_stash_id;
    dshash_delete_entry(pgsa_stash_dshash, stash);
 
    /*
     * Now remove all the entries. Since pgsa_state->lock must be held at
     * least in shared mode to insert entries into pgsa_entry_dshash, it
     * doesn't matter whether we do this before or after deleting the entry
     * from pgsa_stash_dshash.
     */
    dshash_seq_init(&iterator, pgsa_entry_dshash, true);
    while ((entry = dshash_seq_next(&iterator)) != NULL)
    {
        if (stash_id == entry->key.pgsa_stash_id)
        {
            if (entry->advice_string != InvalidDsaPointer)
                dsa_free(pgsa_dsa_area, entry->advice_string);
            dshash_delete_current(&iterator);
        }
    }
    dshash_seq_term(&iterator);
 
    /* Bump change count. */
    pg_atomic_add_fetch_u64(&pgsa_state->change_count, 1);
}

References pgsa_entry::advice_string, Assert, pgsa_shared_state::change_count, dsa_free(), dshash_delete_current(), dshash_delete_entry(), dshash_find(), dshash_seq_init(), dshash_seq_next(), dshash_seq_term(), ereport, errcode(), errmsg, ERROR, fb(), InvalidDsaPointer, pgsa_entry::key, pgsa_shared_state::lock, LW_EXCLUSIVE, LWLockHeldByMeInMode(), pg_atomic_add_fetch_u64(), pgsa_dsa_area, pgsa_entry_dshash, pgsa_stash_dshash, pgsa_entry_key::pgsa_stash_id, and pgsa_state.

Referenced by pg_drop_advice_stash().

pgsa_init_shared_state()

static void pgsa_init_shared_state ( void *  ptr, void *  arg  )

static

Definition at line 568 of file pg_stash_advice.c.

{
    pgsa_shared_state *state = (pgsa_shared_state *) ptr;
 
    LWLockInitialize(&state->lock,
                     LWLockNewTrancheId("pg_stash_advice_lock"));
    state->dsa_tranche = LWLockNewTrancheId("pg_stash_advice_dsa");
    state->stash_tranche = LWLockNewTrancheId("pg_stash_advice_stash");
    state->entry_tranche = LWLockNewTrancheId("pg_stash_advice_entry");
    state->next_stash_id = UINT64CONST(1);
    state->area = DSA_HANDLE_INVALID;
    state->stash_hash = DSHASH_HANDLE_INVALID;
    state->entry_hash = DSHASH_HANDLE_INVALID;
    state->bgworker_pid = InvalidPid;
    pg_atomic_init_flag(&state->stashes_ready);
    pg_atomic_init_u64(&state->change_count, 0);
 
    /*
     * If this module was loaded via shared_preload_libraries, then
     * pg_stash_advice_persist is a GUC variable. If it's true, that means
     * that we should lock out manual stash modifications until the dump file
     * has been successfully loaded. If it's false, there's nothing to load,
     * so we set stashes_ready immediately.
     *
     * If this module was not loaded via shared_preload_libraries, then
     * pg_stash_advice_persist is not a GUC variable, but it will be false,
     * which leads to the correct behavior.
     */
    if (!pg_stash_advice_persist)
        pg_atomic_test_set_flag(&state->stashes_ready);
}

References DSA_HANDLE_INVALID, DSHASH_HANDLE_INVALID, InvalidPid, LWLockInitialize(), LWLockNewTrancheId(), pg_atomic_init_flag(), pg_atomic_init_u64(), pg_atomic_test_set_flag(), pg_stash_advice_persist, and UINT64CONST.

Referenced by pgsa_attach().

pgsa_is_identifier()

static bool pgsa_is_identifier ( char *  str )

static

Definition at line 605 of file pg_stash_advice.c.

{
    if (*str >= '0' && *str <= '9')
        return false;
 
    while (*str != '\0')
    {
        char        c = *str++;
 
        if ((c < '0' || c > '9') && (c < 'a' || c > 'z') &&
            (c < 'A' || c > 'Z') && c != '_')
            return false;
    }
 
    return true;
}

References str.

Referenced by pgsa_check_stash_name(), and pgsa_check_stash_name_guc().

pgsa_lookup_stash_id()

uint64 pgsa_lookup_stash_id

(

char *

stash_name

)

Definition at line 628 of file pg_stash_advice.c.

{
    pgsa_stash *stash;
    uint64      stash_id;
 
    /* Search the shared hash table. */
    stash = dshash_find(pgsa_stash_dshash, stash_name, false);
    if (stash == NULL)
        return 0;
    stash_id = stash->pgsa_stash_id;
    dshash_release_lock(pgsa_stash_dshash, stash);
 
    return stash_id;
}

References dshash_find(), dshash_release_lock(), fb(), and pgsa_stash_dshash.

Referenced by pg_get_advice_stash_contents(), pgsa_advisor(), pgsa_clear_advice_string(), and pgsa_set_advice_string().

pgsa_reset_all_stashes()

void pgsa_reset_all_stashes

(

void

)

Definition at line 537 of file pg_stash_advice.c.

{
    dshash_seq_status iter;
    pgsa_entry *entry;
 
    Assert(LWLockHeldByMeInMode(&pgsa_state->lock, LW_EXCLUSIVE));
 
    /* Remove all stashes. */
    dshash_seq_init(&iter, pgsa_stash_dshash, true);
    while (dshash_seq_next(&iter) != NULL)
        dshash_delete_current(&iter);
    dshash_seq_term(&iter);
 
    /* Remove all entries. */
    dshash_seq_init(&iter, pgsa_entry_dshash, true);
    while ((entry = dshash_seq_next(&iter)) != NULL)
    {
        if (entry->advice_string != InvalidDsaPointer)
            dsa_free(pgsa_dsa_area, entry->advice_string);
        dshash_delete_current(&iter);
    }
    dshash_seq_term(&iter);
 
    /* Reset the stash ID counter. */
    pgsa_state->next_stash_id = UINT64CONST(1);
}

References pgsa_entry::advice_string, Assert, dsa_free(), dshash_delete_current(), dshash_seq_init(), dshash_seq_next(), dshash_seq_term(), fb(), InvalidDsaPointer, pgsa_shared_state::lock, LW_EXCLUSIVE, LWLockHeldByMeInMode(), pgsa_shared_state::next_stash_id, pgsa_dsa_area, pgsa_entry_dshash, pgsa_stash_dshash, pgsa_state, and UINT64CONST.

Referenced by pgsa_read_from_disk().

pgsa_set_advice_string()

void pgsa_set_advice_string	(	char *	stash_name,
		int64	queryId,
		char *	advice_string
	)

Definition at line 647 of file pg_stash_advice.c.

{
    pgsa_entry *entry;
    bool        found;
    pgsa_entry_key key;
    uint64      stash_id;
    dsa_pointer new_dp;
    dsa_pointer old_dp;
 
    /*
     * The caller must hold our lock, at least in shared mode.  This is
     * important for two reasons.
     *
     * First, it holds off interrupts, so that we can't bail out of this code
     * after allocating DSA memory for the advice string and before storing
     * the resulting pointer somewhere that others can find it.
     *
     * Second, we need to avoid a race against pgsa_drop_stash(). That
     * function removes a stash_name->stash_id mapping and all the entries for
     * that stash_id. Without the lock, there's a race condition no matter
     * which of those things it does first, because as soon as we've looked up
     * the stash ID, that whole function can execute before we do the rest of
     * our work, which would result in us adding an entry for a stash that no
     * longer exists.
     */
    Assert(LWLockHeldByMe(&pgsa_state->lock));
 
    /* Look up the stash ID. */
    if ((stash_id = pgsa_lookup_stash_id(stash_name)) == 0)
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("advice stash \"%s\" does not exist", stash_name));
 
    /* Allocate space for the advice string. */
    new_dp = dsa_allocate(pgsa_dsa_area, strlen(advice_string) + 1);
    strcpy(dsa_get_address(pgsa_dsa_area, new_dp), advice_string);
 
    /* Attempt to insert an entry into the hash table. */
    memset(&key, 0, sizeof(pgsa_entry_key));
    key.pgsa_stash_id = stash_id;
    key.queryId = queryId;
    entry = dshash_find_or_insert_extended(pgsa_entry_dshash, &key, &found,
                                           DSHASH_INSERT_NO_OOM);
 
    /*
     * If it didn't work, bail out, being careful to free the shared memory
     * we've already allocated before, since error cleanup will not do so.
     */
    if (entry == NULL)
    {
        dsa_free(pgsa_dsa_area, new_dp);
        ereport(ERROR,
                errcode(ERRCODE_OUT_OF_MEMORY),
                errmsg("out of memory"),
                errdetail("could not insert advice string into shared hash table"));
    }
 
    /* Update the entry and release the lock. */
    old_dp = found ? entry->advice_string : InvalidDsaPointer;
    entry->advice_string = new_dp;
    dshash_release_lock(pgsa_entry_dshash, entry);
 
    /*
     * We're not safe from leaks yet!
     *
     * There's now a pointer to new_dp in the entry that we just updated, but
     * that means that there's no longer anything pointing to old_dp.
     */
    if (DsaPointerIsValid(old_dp))
        dsa_free(pgsa_dsa_area, old_dp);
 
    /* Bump change count. */
    pg_atomic_add_fetch_u64(&pgsa_state->change_count, 1);
}

References pgsa_entry::advice_string, Assert, pgsa_shared_state::change_count, dsa_allocate, dsa_free(), dsa_get_address(), DsaPointerIsValid, dshash_find_or_insert_extended(), DSHASH_INSERT_NO_OOM, dshash_release_lock(), ereport, errcode(), errdetail(), errmsg, ERROR, fb(), InvalidDsaPointer, pgsa_shared_state::lock, LWLockHeldByMe(), pg_atomic_add_fetch_u64(), pgsa_dsa_area, pgsa_entry_dshash, pgsa_lookup_stash_id(), and pgsa_state.

Referenced by pg_set_stashed_advice(), and pgsa_restore_entries().

pgsa_start_worker()

void pgsa_start_worker

(

void

)

Definition at line 726 of file pg_stash_advice.c.

{
    BackgroundWorker worker = {0};
    BackgroundWorkerHandle *handle;
    BgwHandleStatus status;
    pid_t       pid;
 
    worker.bgw_flags = BGWORKER_SHMEM_ACCESS;
    worker.bgw_start_time = BgWorkerStart_ConsistentState;
    worker.bgw_restart_time = BGW_DEFAULT_RESTART_INTERVAL;
    strcpy(worker.bgw_library_name, "pg_stash_advice");
    strcpy(worker.bgw_function_name, "pg_stash_advice_worker_main");
    strcpy(worker.bgw_name, "pg_stash_advice worker");
    strcpy(worker.bgw_type, "pg_stash_advice worker");
 
    /*
     * If process_shared_preload_libraries_in_progress = true, we may be in
     * the postmaster, in which case this will really register the worker, or
     * we may be in a child process in an EXEC_BACKEND build, in which case it
     * will silently do nothing (which is the correct behavior).
     */
    if (process_shared_preload_libraries_in_progress)
    {
        RegisterBackgroundWorker(&worker);
        return;
    }
 
    /*
     * If process_shared_preload_libraries_in_progress = false, we're being
     * asked to start the worker after system startup time. In other words,
     * unless this is single-user mode, we're not in the postmaster, so we
     * should use RegisterDynamicBackgroundWorker and then wait for startup to
     * complete. (If we do happen to be in single-user mode, this will error
     * out, which is fine.)
     */
    worker.bgw_notify_pid = MyProcPid;
    if (!RegisterDynamicBackgroundWorker(&worker, &handle))
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
                 errmsg("could not register background process"),
                 errhint("You may need to increase \"max_worker_processes\".")));
    status = WaitForBackgroundWorkerStartup(handle, &pid);
    if (status != BGWH_STARTED)
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
                 errmsg("could not start background process"),
                 errhint("More details may be available in the server log.")));
}

References BGW_DEFAULT_RESTART_INTERVAL, BackgroundWorker::bgw_flags, BackgroundWorker::bgw_function_name, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_name, BackgroundWorker::bgw_notify_pid, BackgroundWorker::bgw_restart_time, BackgroundWorker::bgw_start_time, BackgroundWorker::bgw_type, BGWH_STARTED, BGWORKER_SHMEM_ACCESS, BgWorkerStart_ConsistentState, ereport, errcode(), errhint(), errmsg, ERROR, fb(), MyProcPid, process_shared_preload_libraries_in_progress, RegisterBackgroundWorker(), RegisterDynamicBackgroundWorker(), and WaitForBackgroundWorkerStartup().

Referenced by _PG_init(), and pg_start_stash_advice_worker().

Variable Documentation

PG_MODULE_MAGIC

PG_MODULE_MAGIC

Definition at line 25 of file pg_stash_advice.c.

pg_stash_advice_mcxt

MemoryContext pg_stash_advice_mcxt

static

Definition at line 58 of file pg_stash_advice.c.

Referenced by pgsa_attach().

pg_stash_advice_persist

bool pg_stash_advice_persist = true

Definition at line 48 of file pg_stash_advice.c.

Referenced by _PG_init(), and pgsa_init_shared_state().

pg_stash_advice_persist_interval

int pg_stash_advice_persist_interval = 30

Definition at line 49 of file pg_stash_advice.c.

Referenced by _PG_init(), and pg_stash_advice_worker_main().

pg_stash_advice_stash_name

char* pg_stash_advice_stash_name = ""

static

Definition at line 47 of file pg_stash_advice.c.

Referenced by _PG_init(), and pgsa_advisor().

pgsa_dsa_area

dsa_area* pgsa_dsa_area

Definition at line 53 of file pg_stash_advice.c.

Referenced by pg_get_advice_stash_contents(), pgsa_advisor(), pgsa_attach(), pgsa_clear_advice_string(), pgsa_drop_stash(), pgsa_reset_all_stashes(), pgsa_set_advice_string(), and pgsa_write_entries().

pgsa_entry_dshash

dshash_table* pgsa_entry_dshash

Definition at line 55 of file pg_stash_advice.c.

Referenced by pg_create_advice_stash(), pg_drop_advice_stash(), pg_get_advice_stash_contents(), pg_get_advice_stashes(), pg_set_stashed_advice(), pg_start_stash_advice_worker(), pgsa_advisor(), pgsa_attach(), pgsa_clear_advice_string(), pgsa_drop_stash(), pgsa_read_from_disk(), pgsa_reset_all_stashes(), pgsa_set_advice_string(), pgsa_write_entries(), and pgsa_write_to_disk().

pgsa_entry_dshash_parameters

dshash_parameters pgsa_entry_dshash_parameters

static

Initial value:

= {
    sizeof(pgsa_entry_key),
    sizeof(pgsa_entry),
    dshash_memcmp,
    dshash_memhash,
    dshash_memcpy,
    LWTRANCHE_INVALID           
}

Definition at line 37 of file pg_stash_advice.c.

                                                        {
    sizeof(pgsa_entry_key),
    sizeof(pgsa_entry),
    dshash_memcmp,
    dshash_memhash,
    dshash_memcpy,
    LWTRANCHE_INVALID           /* gets set at runtime */
};

Referenced by pgsa_attach().

pgsa_stash_dshash

dshash_table* pgsa_stash_dshash

Definition at line 54 of file pg_stash_advice.c.

Referenced by pg_get_advice_stash_contents(), pg_get_advice_stashes(), pgsa_attach(), pgsa_create_stash(), pgsa_drop_stash(), pgsa_lookup_stash_id(), pgsa_reset_all_stashes(), and pgsa_write_stashes().

pgsa_stash_dshash_parameters

dshash_parameters pgsa_stash_dshash_parameters

static

Initial value:

= {
    NAMEDATALEN,
    sizeof(pgsa_stash),
    dshash_strcmp,
    dshash_strhash,
    dshash_strcpy,
    LWTRANCHE_INVALID           
}

Definition at line 28 of file pg_stash_advice.c.

                                                        {
    NAMEDATALEN,
    sizeof(pgsa_stash),
    dshash_strcmp,
    dshash_strhash,
    dshash_strcpy,
    LWTRANCHE_INVALID           /* gets set at runtime */
};

Referenced by pgsa_attach().

pgsa_state

pgsa_shared_state* pgsa_state

Definition at line 52 of file pg_stash_advice.c.

Referenced by pg_create_advice_stash(), pg_drop_advice_stash(), pg_get_advice_stash_contents(), pg_get_advice_stashes(), pg_set_stashed_advice(), pg_start_stash_advice_worker(), pg_stash_advice_worker_main(), pgsa_advisor(), pgsa_attach(), pgsa_check_lockout(), pgsa_clear_advice_string(), pgsa_create_stash(), pgsa_detach_shmem(), pgsa_drop_stash(), pgsa_read_from_disk(), pgsa_reset_all_stashes(), pgsa_restore_entries(), pgsa_restore_stashes(), and pgsa_set_advice_string().