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sqlite3/ext/misc/memstat.c

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/*
** 2018-09-27
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file demonstrates an eponymous virtual table that returns information
** from sqlite3_status64() and sqlite3_db_status().
**
** Usage example:
**
** .load ./memstat
** .mode quote
** .header on
** SELECT * FROM memstat;
*/
#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_MEMSTATVTAB)
#if !defined(SQLITEINT_H)
#include "sqlite3ext.h"
#endif
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
/* memstat_vtab is a subclass of sqlite3_vtab which will
** serve as the underlying representation of a memstat virtual table
*/
typedef struct memstat_vtab memstat_vtab;
struct memstat_vtab {
sqlite3_vtab base; /* Base class - must be first */
sqlite3 *db; /* Database connection for this memstat vtab */
};
/* memstat_cursor is a subclass of sqlite3_vtab_cursor which will
** serve as the underlying representation of a cursor that scans
** over rows of the result
*/
typedef struct memstat_cursor memstat_cursor;
struct memstat_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3 *db; /* Database connection for this cursor */
int iRowid; /* Current row in aMemstatColumn[] */
int iDb; /* Which schema we are looking at */
int nDb; /* Number of schemas */
char **azDb; /* Names of all schemas */
sqlite3_int64 aVal[2]; /* Result values */
};
/*
** The memstatConnect() method is invoked to create a new
** memstat_vtab that describes the memstat virtual table.
**
** Think of this routine as the constructor for memstat_vtab objects.
**
** All this routine needs to do is:
**
** (1) Allocate the memstat_vtab object and initialize all fields.
**
** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
** result set of queries against memstat will look like.
*/
static int memstatConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
memstat_vtab *pNew;
int rc;
/* Column numbers */
#define MSV_COLUMN_NAME 0 /* Name of quantity being measured */
#define MSV_COLUMN_SCHEMA 1 /* schema name */
#define MSV_COLUMN_VALUE 2 /* Current value */
#define MSV_COLUMN_HIWTR 3 /* Highwater mark */
rc = sqlite3_declare_vtab(db,"CREATE TABLE x(name,schema,value,hiwtr)");
if( rc==SQLITE_OK ){
pNew = sqlite3_malloc( sizeof(*pNew) );
*ppVtab = (sqlite3_vtab*)pNew;
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(*pNew));
pNew->db = db;
}
return rc;
}
/*
** This method is the destructor for memstat_cursor objects.
*/
static int memstatDisconnect(sqlite3_vtab *pVtab){
sqlite3_free(pVtab);
return SQLITE_OK;
}
/*
** Constructor for a new memstat_cursor object.
*/
static int memstatOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
memstat_cursor *pCur;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
pCur->db = ((memstat_vtab*)p)->db;
*ppCursor = &pCur->base;
return SQLITE_OK;
}
/*
** Clear all the schema names from a cursor
*/
static void memstatClearSchema(memstat_cursor *pCur){
int i;
if( pCur->azDb==0 ) return;
for(i=0; i<pCur->nDb; i++){
sqlite3_free(pCur->azDb[i]);
}
sqlite3_free(pCur->azDb);
pCur->azDb = 0;
pCur->nDb = 0;
}
/*
** Fill in the azDb[] array for the cursor.
*/
static int memstatFindSchemas(memstat_cursor *pCur){
sqlite3_stmt *pStmt = 0;
int rc;
if( pCur->nDb ) return SQLITE_OK;
rc = sqlite3_prepare_v2(pCur->db, "PRAGMA database_list", -1, &pStmt, 0);
if( rc ){
sqlite3_finalize(pStmt);
return rc;
}
while( sqlite3_step(pStmt)==SQLITE_ROW ){
char **az, *z;
az = sqlite3_realloc64(pCur->azDb, sizeof(char*)*(pCur->nDb+1));
if( az==0 ){
memstatClearSchema(pCur);
return SQLITE_NOMEM;
}
pCur->azDb = az;
z = sqlite3_mprintf("%s", sqlite3_column_text(pStmt, 1));
if( z==0 ){
memstatClearSchema(pCur);
return SQLITE_NOMEM;
}
pCur->azDb[pCur->nDb] = z;
pCur->nDb++;
}
sqlite3_finalize(pStmt);
return SQLITE_OK;
}
/*
** Destructor for a memstat_cursor.
*/
static int memstatClose(sqlite3_vtab_cursor *cur){
memstat_cursor *pCur = (memstat_cursor*)cur;
memstatClearSchema(pCur);
sqlite3_free(cur);
return SQLITE_OK;
}
/*
** Allowed values for aMemstatColumn[].eType
*/
#define MSV_GSTAT 0 /* sqlite3_status64() information */
#define MSV_DB 1 /* sqlite3_db_status() information */
#define MSV_ZIPVFS 2 /* ZIPVFS file-control with 64-bit return */
/*
** An array of quantities that can be measured and reported by
** this virtual table
*/
static const struct MemstatColumns {
const char *zName; /* Symbolic name */
unsigned char eType; /* Type of interface */
unsigned char mNull; /* Bitmask of which columns are NULL */
/* 2: dbname, 4: current, 8: hiwtr */
int eOp; /* Opcode */
} aMemstatColumn[] = {
{"MEMORY_USED", MSV_GSTAT, 2, SQLITE_STATUS_MEMORY_USED },
{"MALLOC_SIZE", MSV_GSTAT, 6, SQLITE_STATUS_MALLOC_SIZE },
{"MALLOC_COUNT", MSV_GSTAT, 2, SQLITE_STATUS_MALLOC_COUNT },
{"PAGECACHE_USED", MSV_GSTAT, 2, SQLITE_STATUS_PAGECACHE_USED },
{"PAGECACHE_OVERFLOW", MSV_GSTAT, 2, SQLITE_STATUS_PAGECACHE_OVERFLOW },
{"PAGECACHE_SIZE", MSV_GSTAT, 6, SQLITE_STATUS_PAGECACHE_SIZE },
{"PARSER_STACK", MSV_GSTAT, 6, SQLITE_STATUS_PARSER_STACK },
{"DB_LOOKASIDE_USED", MSV_DB, 2, SQLITE_DBSTATUS_LOOKASIDE_USED },
{"DB_LOOKASIDE_HIT", MSV_DB, 6, SQLITE_DBSTATUS_LOOKASIDE_HIT },
{"DB_LOOKASIDE_MISS_SIZE", MSV_DB, 6, SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE},
{"DB_LOOKASIDE_MISS_FULL", MSV_DB, 6, SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL},
{"DB_CACHE_USED", MSV_DB, 10, SQLITE_DBSTATUS_CACHE_USED },
#if SQLITE_VERSION_NUMBER >= 3140000
{"DB_CACHE_USED_SHARED", MSV_DB, 10, SQLITE_DBSTATUS_CACHE_USED_SHARED },
#endif
{"DB_SCHEMA_USED", MSV_DB, 10, SQLITE_DBSTATUS_SCHEMA_USED },
{"DB_STMT_USED", MSV_DB, 10, SQLITE_DBSTATUS_STMT_USED },
{"DB_CACHE_HIT", MSV_DB, 10, SQLITE_DBSTATUS_CACHE_HIT },
{"DB_CACHE_MISS", MSV_DB, 10, SQLITE_DBSTATUS_CACHE_MISS },
{"DB_CACHE_WRITE", MSV_DB, 10, SQLITE_DBSTATUS_CACHE_WRITE },
#if SQLITE_VERSION_NUMBER >= 3230000
{"DB_CACHE_SPILL", MSV_DB, 10, SQLITE_DBSTATUS_CACHE_SPILL },
#endif
{"DB_DEFERRED_FKS", MSV_DB, 10, SQLITE_DBSTATUS_DEFERRED_FKS },
#ifdef SQLITE_ENABLE_ZIPVFS
{"ZIPVFS_CACHE_USED", MSV_ZIPVFS, 8, 231454 },
{"ZIPVFS_CACHE_HIT", MSV_ZIPVFS, 8, 231455 },
{"ZIPVFS_CACHE_MISS", MSV_ZIPVFS, 8, 231456 },
{"ZIPVFS_CACHE_WRITE", MSV_ZIPVFS, 8, 231457 },
{"ZIPVFS_DIRECT_READ", MSV_ZIPVFS, 8, 231458 },
{"ZIPVFS_DIRECT_BYTES", MSV_ZIPVFS, 8, 231459 },
#endif /* SQLITE_ENABLE_ZIPVFS */
};
#define MSV_NROW (sizeof(aMemstatColumn)/sizeof(aMemstatColumn[0]))
/*
** Advance a memstat_cursor to its next row of output.
*/
static int memstatNext(sqlite3_vtab_cursor *cur){
memstat_cursor *pCur = (memstat_cursor*)cur;
int i;
assert( pCur->iRowid<=MSV_NROW );
while(1){
i = (int)pCur->iRowid - 1;
if( i<0 || (aMemstatColumn[i].mNull & 2)!=0 || (++pCur->iDb)>=pCur->nDb ){
pCur->iRowid++;
if( pCur->iRowid>MSV_NROW ) return SQLITE_OK; /* End of the table */
pCur->iDb = 0;
i++;
}
pCur->aVal[0] = 0;
pCur->aVal[1] = 0;
switch( aMemstatColumn[i].eType ){
case MSV_GSTAT: {
if( sqlite3_libversion_number()>=3010000 ){
sqlite3_status64(aMemstatColumn[i].eOp,
&pCur->aVal[0], &pCur->aVal[1],0);
}else{
int xCur, xHiwtr;
sqlite3_status(aMemstatColumn[i].eOp, &xCur, &xHiwtr, 0);
pCur->aVal[0] = xCur;
pCur->aVal[1] = xHiwtr;
}
break;
}
case MSV_DB: {
int xCur, xHiwtr;
sqlite3_db_status(pCur->db, aMemstatColumn[i].eOp, &xCur, &xHiwtr, 0);
pCur->aVal[0] = xCur;
pCur->aVal[1] = xHiwtr;
break;
}
case MSV_ZIPVFS: {
int rc;
rc = sqlite3_file_control(pCur->db, pCur->azDb[pCur->iDb],
aMemstatColumn[i].eOp, (void*)&pCur->aVal[0]);
if( rc!=SQLITE_OK ) continue;
break;
}
}
break;
}
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the memstat_cursor
** is currently pointing.
*/
static int memstatColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int iCol /* Which column to return */
){
memstat_cursor *pCur = (memstat_cursor*)cur;
int i;
assert( pCur->iRowid>0 && pCur->iRowid<=MSV_NROW );
i = (int)pCur->iRowid - 1;
if( (aMemstatColumn[i].mNull & (1<<iCol))!=0 ){
return SQLITE_OK;
}
switch( iCol ){
case MSV_COLUMN_NAME: {
sqlite3_result_text(ctx, aMemstatColumn[i].zName, -1, SQLITE_STATIC);
break;
}
case MSV_COLUMN_SCHEMA: {
sqlite3_result_text(ctx, pCur->azDb[pCur->iDb], -1, 0);
break;
}
case MSV_COLUMN_VALUE: {
sqlite3_result_int64(ctx, pCur->aVal[0]);
break;
}
case MSV_COLUMN_HIWTR: {
sqlite3_result_int64(ctx, pCur->aVal[1]);
break;
}
}
return SQLITE_OK;
}
/*
** Return the rowid for the current row. In this implementation, the
** rowid is the same as the output value.
*/
static int memstatRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
memstat_cursor *pCur = (memstat_cursor*)cur;
*pRowid = pCur->iRowid*1000 + pCur->iDb;
return SQLITE_OK;
}
/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int memstatEof(sqlite3_vtab_cursor *cur){
memstat_cursor *pCur = (memstat_cursor*)cur;
return pCur->iRowid>MSV_NROW;
}
/*
** This method is called to "rewind" the memstat_cursor object back
** to the first row of output. This method is always called at least
** once prior to any call to memstatColumn() or memstatRowid() or
** memstatEof().
*/
static int memstatFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
memstat_cursor *pCur = (memstat_cursor *)pVtabCursor;
int rc = memstatFindSchemas(pCur);
if( rc ) return rc;
pCur->iRowid = 0;
pCur->iDb = 0;
return memstatNext(pVtabCursor);
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the memstat virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
*/
static int memstatBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
pIdxInfo->estimatedCost = (double)500;
pIdxInfo->estimatedRows = 500;
return SQLITE_OK;
}
/*
** This following structure defines all the methods for the
** memstat virtual table.
*/
static sqlite3_module memstatModule = {
0, /* iVersion */
0, /* xCreate */
memstatConnect, /* xConnect */
memstatBestIndex, /* xBestIndex */
memstatDisconnect, /* xDisconnect */
0, /* xDestroy */
memstatOpen, /* xOpen - open a cursor */
memstatClose, /* xClose - close a cursor */
memstatFilter, /* xFilter - configure scan constraints */
memstatNext, /* xNext - advance a cursor */
memstatEof, /* xEof - check for end of scan */
memstatColumn, /* xColumn - read data */
memstatRowid, /* xRowid - read data */
0, /* xUpdate */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
0, /* xSavepoint */
0, /* xRelease */
0, /* xRollbackTo */
0, /* xShadowName */
};
#endif /* SQLITE_OMIT_VIRTUALTABLE */
int sqlite3MemstatVtabInit(sqlite3 *db){
int rc = SQLITE_OK;
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3_create_module(db, "sqlite_memstat", &memstatModule, 0);
#endif
return rc;
}
#ifndef SQLITE_CORE
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_memstat_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3MemstatVtabInit(db);
#endif
return rc;
}
#endif /* SQLITE_CORE */
#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_MEMSTATVTAB) */
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