pg_stash_advice.h File Reference

#include "lib/dshash.h"
#include "storage/lwlock.h"
#include "lib/simplehash.h"

Include dependency graph for pg_stash_advice.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Data Structures
struct	pgsa_entry_key
struct	pgsa_entry
struct	pgsa_stash
struct	pgsa_shared_state
struct	pgsa_stash_name

Macros
#define	SH_PREFIX   pgsa_stash_name_table
#define	SH_ELEMENT_TYPE   pgsa_stash_name
#define	SH_KEY_TYPE   uint64
#define	SH_SCOPE   extern
#define	SH_DECLARE

Typedefs
typedef struct pgsa_entry_key	pgsa_entry_key
typedef struct pgsa_entry	pgsa_entry
typedef struct pgsa_stash	pgsa_stash
typedef struct pgsa_shared_state	pgsa_shared_state
typedef struct pgsa_stash_name	pgsa_stash_name

Functions
void	pgsa_attach (void)
void	pgsa_check_stash_name (char *stash_name)
void	pgsa_clear_advice_string (char *stash_name, int64 queryId)
void	pgsa_create_stash (char *stash_name)
void	pgsa_drop_stash (char *stash_name)
uint64	pgsa_lookup_stash_id (char *stash_name)
void	pgsa_set_advice_string (char *stash_name, int64 queryId, char *advice_string)

Variables
pgsa_shared_state *	pgsa_state
dsa_area *	pgsa_dsa_area
dshash_table *	pgsa_stash_dshash
dshash_table *	pgsa_entry_dshash

Macro Definition Documentation

SH_DECLARE

#define SH_DECLARE

Definition at line 80 of file pg_stash_advice.h.

SH_ELEMENT_TYPE

#define SH_ELEMENT_TYPE   pgsa_stash_name

Definition at line 77 of file pg_stash_advice.h.

SH_KEY_TYPE

#define SH_KEY_TYPE   uint64

Definition at line 78 of file pg_stash_advice.h.

SH_PREFIX

#define SH_PREFIX   pgsa_stash_name_table

Definition at line 76 of file pg_stash_advice.h.

SH_SCOPE

#define SH_SCOPE   extern

Definition at line 79 of file pg_stash_advice.h.

Typedef Documentation

pgsa_entry

typedef struct pgsa_entry pgsa_entry

pgsa_entry_key

typedef struct pgsa_entry_key pgsa_entry_key

pgsa_shared_state

typedef struct pgsa_shared_state pgsa_shared_state

pgsa_stash

typedef struct pgsa_stash pgsa_stash

pgsa_stash_name

typedef struct pgsa_stash_name pgsa_stash_name

Function Documentation

pgsa_attach()

void pgsa_attach ( void  )

extern

Definition at line 182 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(), and pgsa_advisor().

pgsa_check_stash_name()

void pgsa_check_stash_name ( char *  stash_name )

extern

Definition at line 288 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_clear_advice_string()

void pgsa_clear_advice_string ( char *  stash_name, int64  queryId  )

extern

Definition at line 392 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);
}

References pgsa_entry::advice_string, Assert, dsa_free(), dshash_delete_entry(), dshash_find(), ereport, errcode(), errmsg, ERROR, fb(), InvalidDsaPointer, pgsa_shared_state::lock, LWLockHeldByMe(), 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 )

extern

Definition at line 371 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);
}

References Assert, 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, pgsa_stash_dshash, and pgsa_state.

Referenced by pg_create_advice_stash().

pgsa_drop_stash()

void pgsa_drop_stash ( char *  stash_name )

extern

Definition at line 432 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);
}

References pgsa_entry::advice_string, Assert, 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(), 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_lookup_stash_id()

uint64 pgsa_lookup_stash_id ( char *  stash_name )

extern

Definition at line 516 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_set_advice_string()

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

extern

Definition at line 535 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);
}

References pgsa_entry::advice_string, Assert, 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(), pgsa_dsa_area, pgsa_entry_dshash, pgsa_lookup_stash_id(), and pgsa_state.

Referenced by pg_set_stashed_advice().

Variable Documentation

pgsa_dsa_area

dsa_area* pgsa_dsa_area

extern

Definition at line 49 of file pg_stash_advice.c.

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

pgsa_entry_dshash

dshash_table* pgsa_entry_dshash

extern

Definition at line 51 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(), pgsa_advisor(), pgsa_attach(), pgsa_clear_advice_string(), pgsa_drop_stash(), and pgsa_set_advice_string().

pgsa_stash_dshash

dshash_table* pgsa_stash_dshash

extern

Definition at line 50 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(), and pgsa_lookup_stash_id().

pgsa_state

pgsa_shared_state* pgsa_state

extern

Definition at line 48 of file pg_stash_advice.c.

Referenced by pg_create_advice_stash(), pg_drop_advice_stash(), pg_set_stashed_advice(), pgsa_attach(), pgsa_clear_advice_string(), pgsa_create_stash(), pgsa_drop_stash(), and pgsa_set_advice_string().