--- /dev/null
+/*
+** 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) */
projects / thirdparty / sqlite.git / commitdiff
