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Fix server crash #34

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Fix server crash #34

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19c5c8c
Add -Wformat compiler flag
kovmir Jan 26, 2024
7d27ea2
Fix typo in some variable names
kovmir Jan 26, 2024
572fa77
Do not append snipped plans when out memory
kovmir Jan 26, 2024
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5 changes: 4 additions & 1 deletion Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,10 @@ DATA = pg_show_plans--1.0--1.1.sql \
REGRESS = pg_show_plans formats
DOCS = pg_show_plans.md

# Fix GCC compilation warning against 16:
# cc1: warning: ‘-Wformat-security’ ignored without ‘-Wformat’ [-Wformat-security]
PG_CFLAGS = -Wformat

USE_PGXS = 1
ifdef USE_PGXS
PG_CONFIG = pg_config
Expand All @@ -20,4 +24,3 @@ top_builddir = ../..
include $(top_builddir)/src/Makefile.global
include $(top_srcdir)/contrib/contrib-global.mk
endif

95 changes: 47 additions & 48 deletions pg_show_plans.c
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Original file line number Diff line number Diff line change
Expand Up @@ -61,9 +61,9 @@ typedef struct pgspSharedState /* Shared state of the extension. */

typedef struct pgspCtx { /* Used as `funcctx->user_fctx` in pg_show_plans(). */
HASH_SEQ_STATUS *hash_seq;
pgspEntry *pgvp_tmp_entry; /* PGVP entry currently processing. */
pgspEntry *pgsp_tmp_entry; /* PGSP entry currently processing. */
int curr_nest; /* Current nest level porcessing. */
bool is_done; /* Done processing current PGVP entry? */
bool is_done; /* Done processing current PGSP entry? */
} pgspCtx;

/* Function Prototypes */
Expand Down Expand Up @@ -99,7 +99,7 @@ static bool is_allowed_role(void);
/* Hook functions. */
/* Ask for shared memory. */
#if PG_VERSION_NUM >= 150000
static void pgvp_shmem_request(void);
static void pgsp_shmem_request(void);
#endif
static void pgsp_shmem_startup(void);
/* Saves query plans to the shared hash table. */
Expand Down Expand Up @@ -190,7 +190,7 @@ _PG_init(void)
/* Save old hooks, and install new ones. */
#if PG_VERSION_NUM >= 150000
prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = pgvp_shmem_request;
shmem_request_hook = pgsp_shmem_request;
#else
RequestAddinShmemSpace(shmem_required());
RequestNamedLWLockTranche("pg_show_plans", 1);
Expand Down Expand Up @@ -239,13 +239,13 @@ compare_hash_key(const void *key1, const void *key2, Size keysize)
static int
ensure_cached(void)
{
pgspHashKey pgvp_hash_hey;
pgspHashKey pgsp_hash_hey;

if (pgsp_cache)
return 1;

pgvp_hash_hey.pid = MyProcPid;
pgsp_cache = create_hash_entry(&pgvp_hash_hey);
pgsp_hash_hey.pid = MyProcPid;
pgsp_cache = create_hash_entry(&pgsp_hash_hey);
if (!pgsp_cache)
return 0; /* Ran out of memory. */

Expand Down Expand Up @@ -280,24 +280,23 @@ append_query_plan(ExplainState *es)

offset = 0;
for (i = 0; i < nest_level; i++)
offset += pgsp_cache->plan_len[i] + 1;
offset += pgsp_cache->plan_len[i] + 1; /* +1 for '\0'. */
space_left = max_plan_length - offset;

if (pgsp->plan_format == EXPLAIN_FORMAT_TEXT)
new_plan->len--; /* Discard '\n'. */

if (new_plan->len < space_left) { /* Enough space for a new plan. */
memcpy(pgsp_cache->plan + offset,
new_plan->data, new_plan->len);
pgsp_cache->plan[offset + new_plan->len] = '\0';
pgsp_cache->plan_len[nest_level] = new_plan->len;
} else { /* No space left to hold a new plan, snip it. */
memcpy(pgsp_cache->plan + offset,
new_plan->data, space_left);
pgsp_cache->plan[max_plan_length-1] = '\0';
pgsp_cache->plan[max_plan_length-2] = '|'; /* Snip indicator. */
pgsp_cache->plan_len[nest_level] = space_left;
if (space_left < new_plan->len+1) {
ereport(WARNING,
errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("not enough memory to append new query plans"));
return;
}

memcpy(pgsp_cache->plan + offset,
new_plan->data, new_plan->len);
pgsp_cache->plan[offset + new_plan->len] = '\0';
pgsp_cache->plan_len[nest_level] = new_plan->len;
pgsp_cache->db_id = MyDatabaseId;
pgsp_cache->n_plans = nest_level+1;
}
Expand Down Expand Up @@ -395,7 +394,7 @@ is_allowed_role(void)

#if PG_VERSION_NUM >= 150000
static void
pgvp_shmem_request(void)
pgsp_shmem_request(void)
{
if (prev_shmem_request_hook)
prev_shmem_request_hook();
Expand Down Expand Up @@ -519,9 +518,9 @@ pg_show_plans(PG_FUNCTION_ARGS)
int offset;
int i;

pgspCtx *pgvp_ctx;
pgspCtx *pgsp_ctx;
HASH_SEQ_STATUS *hash_seq;
pgspEntry *pgvp_tmp_entry;
pgspEntry *pgsp_tmp_entry;
int curr_nest;
bool is_done;

Expand All @@ -534,12 +533,12 @@ pg_show_plans(PG_FUNCTION_ARGS)
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

LWLockAcquire(pgsp->lock, LW_SHARED);
pgvp_ctx = (pgspCtx *)palloc(sizeof(pgspCtx));
pgvp_ctx->is_done = true;
pgvp_ctx->curr_nest = 0;
pgvp_ctx->hash_seq = (HASH_SEQ_STATUS *)palloc(sizeof(HASH_SEQ_STATUS));
hash_seq_init(pgvp_ctx->hash_seq, pgsp_hash);
funcctx->user_fctx = (void *)pgvp_ctx;
pgsp_ctx = (pgspCtx *)palloc(sizeof(pgspCtx));
pgsp_ctx->is_done = true;
pgsp_ctx->curr_nest = 0;
pgsp_ctx->hash_seq = (HASH_SEQ_STATUS *)palloc(sizeof(HASH_SEQ_STATUS));
hash_seq_init(pgsp_ctx->hash_seq, pgsp_hash);
funcctx->user_fctx = (void *)pgsp_ctx;
funcctx->max_calls = hash_get_num_entries(pgsp_hash);

if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
Expand All @@ -554,11 +553,11 @@ pg_show_plans(PG_FUNCTION_ARGS)

funcctx = SRF_PERCALL_SETUP();
/* Restore context. */
pgvp_ctx = (pgspCtx *)funcctx->user_fctx;
hash_seq = pgvp_ctx->hash_seq;
is_done = pgvp_ctx->is_done;
pgvp_tmp_entry = pgvp_ctx->pgvp_tmp_entry;
curr_nest = pgvp_ctx->curr_nest;
pgsp_ctx = (pgspCtx *)funcctx->user_fctx;
hash_seq = pgsp_ctx->hash_seq;
is_done = pgsp_ctx->is_done;
pgsp_tmp_entry = pgsp_ctx->pgsp_tmp_entry;
curr_nest = pgsp_ctx->curr_nest;
/* Pull other stuff from `funcctx`. */
call_cntr = funcctx->call_cntr;
max_calls = funcctx->max_calls;
Expand All @@ -570,55 +569,55 @@ pg_show_plans(PG_FUNCTION_ARGS)

if (is_done) /* Done processing a hash entry? */
{ /* Grab a new one. */
pgvp_tmp_entry = hash_seq_search(hash_seq);
pgsp_tmp_entry = hash_seq_search(hash_seq);
/* Skip empty entries and the ones the user is not
* allowed to see. */
for (;;) {
if (pgvp_tmp_entry->n_plans >= 1) {
if (pgsp_tmp_entry->n_plans >= 1) {
if (is_allowed_role())
break;
else if (pgvp_tmp_entry->user_id == GetUserId())
else if (pgsp_tmp_entry->user_id == GetUserId())
break;
}
if (call_cntr == max_calls-1) { /* No more entries. */
hash_seq_term(hash_seq);
LWLockRelease(pgsp->lock);
SRF_RETURN_DONE(funcctx);
}
pgvp_tmp_entry = hash_seq_search(hash_seq);
pgsp_tmp_entry = hash_seq_search(hash_seq);
call_cntr++;
}
SpinLockAcquire(&pgvp_tmp_entry->mutex);
SpinLockAcquire(&pgsp_tmp_entry->mutex);
}

/* A single hash entry may store multiple (nested) plans, so
* count offset to get the desired plan. */
offset = 0;
for (i = 0; i < curr_nest; i++)
offset += pgvp_tmp_entry->plan_len[i] + 1;
offset += pgsp_tmp_entry->plan_len[i] + 1;

MemSet(nulls, 0, sizeof(nulls));
values[0] = Int32GetDatum(pgvp_tmp_entry->hash_key.pid);
values[0] = Int32GetDatum(pgsp_tmp_entry->hash_key.pid);
values[1] = Int32GetDatum(curr_nest);
values[2] = ObjectIdGetDatum(pgvp_tmp_entry->user_id);
values[3] = ObjectIdGetDatum(pgvp_tmp_entry->db_id);
values[4] = CStringGetTextDatum(pgvp_tmp_entry->plan + offset);
values[2] = ObjectIdGetDatum(pgsp_tmp_entry->user_id);
values[3] = ObjectIdGetDatum(pgsp_tmp_entry->db_id);
values[4] = CStringGetTextDatum(pgsp_tmp_entry->plan + offset);
htup = heap_form_tuple(funcctx->tuple_desc, values, nulls);

if (curr_nest < pgvp_tmp_entry->n_plans-1)
if (curr_nest < pgsp_tmp_entry->n_plans-1)
{ /* Still have nested plans. */
curr_nest++;
call_cntr--; /* May not be legal, but it works. */
is_done = false;
} else { /* No more nested plans, get a new entry. */
curr_nest = 0;
is_done = true;
SpinLockRelease(&pgvp_tmp_entry->mutex);
SpinLockRelease(&pgsp_tmp_entry->mutex);
}
/* Save values back to the context. */
pgvp_ctx->is_done = is_done;
pgvp_ctx->curr_nest = curr_nest;
pgvp_ctx->pgvp_tmp_entry = pgvp_tmp_entry;
pgsp_ctx->is_done = is_done;
pgsp_ctx->curr_nest = curr_nest;
pgsp_ctx->pgsp_tmp_entry = pgsp_tmp_entry;
funcctx->call_cntr = call_cntr;

SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(htup));
Expand Down
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