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Initial prototype of a eponymous virtual table that accesses sqlite3_status64()

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and sqlite3_db_status().

FossilOrigin-Name: 0b44e1f68e0c8349367e3f929d4734c3df96338ec8d6fb652565bf894e8b8343
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drh 2018-09-27 15:21:13 +00:00
parent 6afa35c985
commit d7fda6cfc5
3 changed files with 327 additions and 7 deletions
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316
ext/misc/memstat.c Normal file
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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_STMTVTAB)
#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 */
sqlite3_int64 iRowid; /* The rowid */
sqlite3_int64 iCur; /* Current value */
sqlite3_int64 iHiwtr; /* High-water mark */
};
/*
** 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_CURRENT 1 /* Current value */
#define MSV_COLUMN_HIWTR 2 /* Highwater mark */
rc = sqlite3_declare_vtab(db,"CREATE TABLE x(name,current,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;
}
/*
** Destructor for a memstat_cursor.
*/
static int memstatClose(sqlite3_vtab_cursor *cur){
sqlite3_free(cur);
return SQLITE_OK;
}
/*
** Allowed values for aMemstatColumn[].eType
*/
#define MSV_GSTAT 0 /* sqlite3_status64() information */
#define MSV_DBSTAT 1 /* sqlite3_db_status() information */
/*
** An array of quantities that can be measured and reported by
** this virtual table
*/
static const struct MemstatColumns {
const char *zName; /* Symbolic name */
int eType; /* Type of interface */
int eOp; /* Opcode */
} aMemstatColumn[] = {
{ "MEMORY_USED", MSV_GSTAT, SQLITE_STATUS_MEMORY_USED },
{ "MALLOC_SIZE", MSV_GSTAT, SQLITE_STATUS_MALLOC_SIZE },
{ "MALLOC_COUNT", MSV_GSTAT, SQLITE_STATUS_MALLOC_COUNT },
{ "PAGECACHE_USED", MSV_GSTAT, SQLITE_STATUS_PAGECACHE_USED },
{ "PAGECACHE_OVERFLOW", MSV_GSTAT, SQLITE_STATUS_PAGECACHE_OVERFLOW },
{ "PAGECACHE_SIZE", MSV_GSTAT, SQLITE_STATUS_PAGECACHE_SIZE },
{ "PARSER_STACK", MSV_GSTAT, SQLITE_STATUS_PARSER_STACK },
{ "LOOKASIDE_USED", MSV_DBSTAT, SQLITE_DBSTATUS_LOOKASIDE_USED },
{ "CACHE_USED", MSV_DBSTAT, SQLITE_DBSTATUS_CACHE_USED },
{ "SCHEMA_USED", MSV_DBSTAT, SQLITE_DBSTATUS_SCHEMA_USED },
{ "STMT_USED", MSV_DBSTAT, SQLITE_DBSTATUS_STMT_USED },
{ "LOOKASIDE_HIT", MSV_DBSTAT, SQLITE_DBSTATUS_LOOKASIDE_HIT },
{ "LOOKASIDE_MISS_SIZE", MSV_DBSTAT, SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE },
{ "LOOKASIDE_MISS_FULL", MSV_DBSTAT, SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL },
{ "CACHE_HIT", MSV_DBSTAT, SQLITE_DBSTATUS_CACHE_HIT },
{ "CACHE_MISS", MSV_DBSTAT, SQLITE_DBSTATUS_CACHE_MISS },
{ "CACHE_WRITE", MSV_DBSTAT, SQLITE_DBSTATUS_CACHE_WRITE },
{ "DEFERRED_FKS", MSV_DBSTAT, SQLITE_DBSTATUS_DEFERRED_FKS },
{ "CACHE_USED_SHARED", MSV_DBSTAT, SQLITE_DBSTATUS_CACHE_USED_SHARED },
{ "CACHE_SPILL", MSV_DBSTAT, SQLITE_DBSTATUS_CACHE_SPILL },
};
#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;
pCur->iRowid++;
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;
sqlite3_int64 iCur = 0, iHiwtr = 0;
assert( pCur->iRowid>0 && pCur->iRowid<=MSV_NROW );
i = (int)pCur->iRowid - 1;
if( iCol==MSV_COLUMN_NAME ){
sqlite3_result_text(ctx, aMemstatColumn[i].zName, -1, SQLITE_STATIC);
return SQLITE_OK;
}
switch( aMemstatColumn[i].eType ){
case MSV_GSTAT: {
sqlite3_status64(aMemstatColumn[i].eOp, &iCur, &iHiwtr, 0);
break;
}
case MSV_DBSTAT: {
int xCur, xHiwtr;
sqlite3_db_status(pCur->db, aMemstatColumn[i].eOp, &xCur, &xHiwtr, 0);
iCur = xCur;
iHiwtr = xHiwtr;
break;
}
}
if( iCol==MSV_COLUMN_HIWTR ) iCur = iHiwtr;
sqlite3_result_int64(ctx, iCur);
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;
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;
pCur->iRowid = 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 */
};
#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_STMTVTAB) */

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