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sqlite/ext/misc/completion.c

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/*
** 2017-07-10
**
** 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 implements an eponymous virtual table that returns suggested
** completions for a partial SQL input.
**
** Suggested usage:
**
** SELECT DISTINCT candidate COLLATE nocase
** FROM completion($prefix,$wholeline)
** ORDER BY 1;
**
** The two query parameters are optional. $prefix is the text of the
** current word being typed and that is to be completed. $wholeline is
** the complete input line, used for context.
**
** The raw completion() table might return the same candidate multiple
** times, for example if the same column name is used to two or more
** tables. And the candidates are returned in an arbitrary order. Hence,
** the DISTINCT and ORDER BY are recommended.
**
** This virtual table operates at the speed of human typing, and so there
** is no attempt to make it fast. Even a slow implementation will be much
** faster than any human can type.
**
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#include <ctype.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
/* completion_vtab is a subclass of sqlite3_vtab which will
** serve as the underlying representation of a completion virtual table
*/
typedef struct completion_vtab completion_vtab;
struct completion_vtab {
sqlite3_vtab base; /* Base class - must be first */
sqlite3 *db; /* Database connection for this completion vtab */
};
/* completion_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 completion_cursor completion_cursor;
struct completion_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3 *db; /* Database connection for this cursor */
int nPrefix, nLine; /* Number of bytes in zPrefix and zLine */
char *zPrefix; /* The prefix for the word we want to complete */
char *zLine; /* The whole that we want to complete */
const char *zCurrentRow; /* Current output row */
int szRow; /* Length of the zCurrentRow string */
sqlite3_stmt *pStmt; /* Current statement */
sqlite3_int64 iRowid; /* The rowid */
int ePhase; /* Current phase */
int j; /* inter-phase counter */
};
/* Values for ePhase:
*/
#define COMPLETION_FIRST_PHASE 1
#define COMPLETION_KEYWORDS 1
#define COMPLETION_PRAGMAS 2
#define COMPLETION_FUNCTIONS 3
#define COMPLETION_COLLATIONS 4
#define COMPLETION_INDEXES 5
#define COMPLETION_TRIGGERS 6
#define COMPLETION_DATABASES 7
#define COMPLETION_TABLES 8 /* Also VIEWs and TRIGGERs */
#define COMPLETION_COLUMNS 9
#define COMPLETION_MODULES 10
#define COMPLETION_EOF 11
/*
** The completionConnect() method is invoked to create a new
** completion_vtab that describes the completion virtual table.
**
** Think of this routine as the constructor for completion_vtab objects.
**
** All this routine needs to do is:
**
** (1) Allocate the completion_vtab object and initialize all fields.
**
** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
** result set of queries against completion will look like.
*/
static int completionConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
completion_vtab *pNew;
int rc;
(void)(pAux); /* Unused parameter */
(void)(argc); /* Unused parameter */
(void)(argv); /* Unused parameter */
(void)(pzErr); /* Unused parameter */
/* Column numbers */
#define COMPLETION_COLUMN_CANDIDATE 0 /* Suggested completion of the input */
#define COMPLETION_COLUMN_PREFIX 1 /* Prefix of the word to be completed */
#define COMPLETION_COLUMN_WHOLELINE 2 /* Entire line seen so far */
#define COMPLETION_COLUMN_PHASE 3 /* ePhase - used for debugging only */
sqlite3_vtab_config(db, SQLITE_VTAB_INNOCUOUS);
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x("
" candidate TEXT,"
" prefix TEXT HIDDEN,"
" wholeline TEXT HIDDEN,"
" phase INT HIDDEN" /* Used for debugging only */
")");
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 completion_cursor objects.
*/
static int completionDisconnect(sqlite3_vtab *pVtab){
sqlite3_free(pVtab);
return SQLITE_OK;
}
/*
** Constructor for a new completion_cursor object.
*/
static int completionOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
completion_cursor *pCur;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
pCur->db = ((completion_vtab*)p)->db;
*ppCursor = &pCur->base;
return SQLITE_OK;
}
/*
** Reset the completion_cursor.
*/
static void completionCursorReset(completion_cursor *pCur){
sqlite3_free(pCur->zPrefix); pCur->zPrefix = 0; pCur->nPrefix = 0;
sqlite3_free(pCur->zLine); pCur->zLine = 0; pCur->nLine = 0;
sqlite3_finalize(pCur->pStmt); pCur->pStmt = 0;
pCur->j = 0;
}
/*
** Destructor for a completion_cursor.
*/
static int completionClose(sqlite3_vtab_cursor *cur){
completionCursorReset((completion_cursor*)cur);
sqlite3_free(cur);
return SQLITE_OK;
}
/*
** Advance a completion_cursor to its next row of output.
**
** The ->ePhase, ->j, and ->pStmt fields of the completion_cursor object
** record the current state of the scan. This routine sets ->zCurrentRow
** to the current row of output and then returns. If no more rows remain,
** then ->ePhase is set to COMPLETION_EOF which will signal the virtual
** table that has reached the end of its scan.
**
** The current implementation just lists potential identifiers and
** keywords and filters them by zPrefix. Future enhancements should
** take zLine into account to try to restrict the set of identifiers and
** keywords based on what would be legal at the current point of input.
*/
static int completionNext(sqlite3_vtab_cursor *cur){
completion_cursor *pCur = (completion_cursor*)cur;
int eNextPhase = 0; /* Next phase to try if current phase reaches end */
int iCol = -1; /* If >=0, step pCur->pStmt and use the i-th column */
pCur->iRowid++;
while( pCur->ePhase!=COMPLETION_EOF ){
switch( pCur->ePhase ){
case COMPLETION_KEYWORDS: {
if( pCur->j >= sqlite3_keyword_count() ){
pCur->zCurrentRow = 0;
pCur->ePhase = COMPLETION_DATABASES;
}else{
sqlite3_keyword_name(pCur->j++, &pCur->zCurrentRow, &pCur->szRow);
}
iCol = -1;
break;
}
case COMPLETION_DATABASES: {
if( pCur->pStmt==0 ){
sqlite3_prepare_v2(pCur->db, "PRAGMA database_list", -1,
&pCur->pStmt, 0);
}
iCol = 1;
eNextPhase = COMPLETION_TABLES;
break;
}
case COMPLETION_TABLES: {
if( pCur->pStmt==0 ){
sqlite3_stmt *pS2;
char *zSql = 0;
const char *zSep = "";
sqlite3_prepare_v2(pCur->db, "PRAGMA database_list", -1, &pS2, 0);
while( sqlite3_step(pS2)==SQLITE_ROW ){
const char *zDb = (const char*)sqlite3_column_text(pS2, 1);
zSql = sqlite3_mprintf(
"%z%s"
"SELECT name FROM \"%w\".sqlite_schema",
zSql, zSep, zDb
);
if( zSql==0 ) return SQLITE_NOMEM;
zSep = " UNION ";
}
sqlite3_finalize(pS2);
sqlite3_prepare_v2(pCur->db, zSql, -1, &pCur->pStmt, 0);
sqlite3_free(zSql);
}
iCol = 0;
eNextPhase = COMPLETION_COLUMNS;
break;
}
case COMPLETION_COLUMNS: {
if( pCur->pStmt==0 ){
sqlite3_stmt *pS2;
char *zSql = 0;
const char *zSep = "";
sqlite3_prepare_v2(pCur->db, "PRAGMA database_list", -1, &pS2, 0);
while( sqlite3_step(pS2)==SQLITE_ROW ){
const char *zDb = (const char*)sqlite3_column_text(pS2, 1);
zSql = sqlite3_mprintf(
"%z%s"
"SELECT pti.name FROM \"%w\".sqlite_schema AS sm"
" JOIN pragma_table_xinfo(sm.name,%Q) AS pti"
" WHERE sm.type='table'",
zSql, zSep, zDb, zDb
);
if( zSql==0 ) return SQLITE_NOMEM;
zSep = " UNION ";
}
sqlite3_finalize(pS2);
sqlite3_prepare_v2(pCur->db, zSql, -1, &pCur->pStmt, 0);
sqlite3_free(zSql);
}
iCol = 0;
eNextPhase = COMPLETION_EOF;
break;
}
}
if( iCol<0 ){
/* This case is when the phase presets zCurrentRow */
if( pCur->zCurrentRow==0 ) continue;
}else{
if( sqlite3_step(pCur->pStmt)==SQLITE_ROW ){
/* Extract the next row of content */
pCur->zCurrentRow = (const char*)sqlite3_column_text(pCur->pStmt, iCol);
pCur->szRow = sqlite3_column_bytes(pCur->pStmt, iCol);
}else{
/* When all rows are finished, advance to the next phase */
sqlite3_finalize(pCur->pStmt);
pCur->pStmt = 0;
pCur->ePhase = eNextPhase;
continue;
}
}
if( pCur->nPrefix==0 ) break;
if( pCur->nPrefix<=pCur->szRow
&& sqlite3_strnicmp(pCur->zPrefix, pCur->zCurrentRow, pCur->nPrefix)==0
){
break;
}
}
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the completion_cursor
** is currently pointing.
*/
static int completionColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int i /* Which column to return */
){
completion_cursor *pCur = (completion_cursor*)cur;
switch( i ){
case COMPLETION_COLUMN_CANDIDATE: {
sqlite3_result_text(ctx, pCur->zCurrentRow, pCur->szRow,SQLITE_TRANSIENT);
break;
}
case COMPLETION_COLUMN_PREFIX: {
sqlite3_result_text(ctx, pCur->zPrefix, -1, SQLITE_TRANSIENT);
break;
}
case COMPLETION_COLUMN_WHOLELINE: {
sqlite3_result_text(ctx, pCur->zLine, -1, SQLITE_TRANSIENT);
break;
}
case COMPLETION_COLUMN_PHASE: {
sqlite3_result_int(ctx, pCur->ePhase);
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 completionRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
completion_cursor *pCur = (completion_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 completionEof(sqlite3_vtab_cursor *cur){
completion_cursor *pCur = (completion_cursor*)cur;
return pCur->ePhase >= COMPLETION_EOF;
}
/*
** This method is called to "rewind" the completion_cursor object back
** to the first row of output. This method is always called at least
** once prior to any call to completionColumn() or completionRowid() or
** completionEof().
*/
static int completionFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
completion_cursor *pCur = (completion_cursor *)pVtabCursor;
int iArg = 0;
(void)(idxStr); /* Unused parameter */
(void)(argc); /* Unused parameter */
completionCursorReset(pCur);
if( idxNum & 1 ){
pCur->nPrefix = sqlite3_value_bytes(argv[iArg]);
if( pCur->nPrefix>0 ){
pCur->zPrefix = sqlite3_mprintf("%s", sqlite3_value_text(argv[iArg]));
if( pCur->zPrefix==0 ) return SQLITE_NOMEM;
}
iArg = 1;
}
if( idxNum & 2 ){
pCur->nLine = sqlite3_value_bytes(argv[iArg]);
if( pCur->nLine>0 ){
pCur->zLine = sqlite3_mprintf("%s", sqlite3_value_text(argv[iArg]));
if( pCur->zLine==0 ) return SQLITE_NOMEM;
}
}
if( pCur->zLine!=0 && pCur->zPrefix==0 ){
int i = pCur->nLine;
while( i>0 && (isalnum(pCur->zLine[i-1]) || pCur->zLine[i-1]=='_') ){
i--;
}
pCur->nPrefix = pCur->nLine - i;
if( pCur->nPrefix>0 ){
pCur->zPrefix = sqlite3_mprintf("%.*s", pCur->nPrefix, pCur->zLine + i);
if( pCur->zPrefix==0 ) return SQLITE_NOMEM;
}
}
pCur->iRowid = 0;
pCur->ePhase = COMPLETION_FIRST_PHASE;
return completionNext(pVtabCursor);
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the completion virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
**
** There are two hidden parameters that act as arguments to the table-valued
** function: "prefix" and "wholeline". Bit 0 of idxNum is set if "prefix"
** is available and bit 1 is set if "wholeline" is available.
*/
static int completionBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
int i; /* Loop over constraints */
int idxNum = 0; /* The query plan bitmask */
int prefixIdx = -1; /* Index of the start= constraint, or -1 if none */
int wholelineIdx = -1; /* Index of the stop= constraint, or -1 if none */
int nArg = 0; /* Number of arguments that completeFilter() expects */
const struct sqlite3_index_constraint *pConstraint;
(void)(tab); /* Unused parameter */
pConstraint = pIdxInfo->aConstraint;
for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
if( pConstraint->usable==0 ) continue;
if( pConstraint->op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
switch( pConstraint->iColumn ){
case COMPLETION_COLUMN_PREFIX:
prefixIdx = i;
idxNum |= 1;
break;
case COMPLETION_COLUMN_WHOLELINE:
wholelineIdx = i;
idxNum |= 2;
break;
}
}
if( prefixIdx>=0 ){
pIdxInfo->aConstraintUsage[prefixIdx].argvIndex = ++nArg;
pIdxInfo->aConstraintUsage[prefixIdx].omit = 1;
}
if( wholelineIdx>=0 ){
pIdxInfo->aConstraintUsage[wholelineIdx].argvIndex = ++nArg;
pIdxInfo->aConstraintUsage[wholelineIdx].omit = 1;
}
pIdxInfo->idxNum = idxNum;
pIdxInfo->estimatedCost = (double)5000 - 1000*nArg;
pIdxInfo->estimatedRows = 500 - 100*nArg;
return SQLITE_OK;
}
/*
** This following structure defines all the methods for the
** completion virtual table.
*/
static sqlite3_module completionModule = {
0, /* iVersion */
0, /* xCreate */
completionConnect, /* xConnect */
completionBestIndex, /* xBestIndex */
completionDisconnect, /* xDisconnect */
0, /* xDestroy */
completionOpen, /* xOpen - open a cursor */
completionClose, /* xClose - close a cursor */
completionFilter, /* xFilter - configure scan constraints */
completionNext, /* xNext - advance a cursor */
completionEof, /* xEof - check for end of scan */
completionColumn, /* xColumn - read data */
completionRowid, /* 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 */
0 /* xIntegrity */
};
#endif /* SQLITE_OMIT_VIRTUALTABLE */
int sqlite3CompletionVtabInit(sqlite3 *db){
int rc = SQLITE_OK;
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3_create_module(db, "completion", &completionModule, 0);
#endif
return rc;
}
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_completion_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
(void)(pzErrMsg); /* Unused parameter */
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3CompletionVtabInit(db);
#endif
return rc;
}
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