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Improve the readability of the unionvtab code.

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FossilOrigin-Name: 5bcf0f86ea7fbbc31a13b2d5b1cf93a92e46fb65fe8e779b3d7e4a98d60d7061
This commit is contained in:
dan
2017-07-18 20:03:49 +00:00
parent 090f68a390
commit 859e4a73b7
3 changed files with 72 additions and 51 deletions
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109
ext/misc/unionvtab.c
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@ -152,31 +152,33 @@ static char *unionStrdup(int *pRc, const char *zIn){
** function is a no-op.
*/
static void unionDequote(char *z){
char q = z[0];
if( z ){
char q = z[0];
/* Set stack variable q to the close-quote character */
if( q=='[' || q=='\'' || q=='"' || q=='`' ){
int iIn = 1;
int iOut = 0;
if( q=='[' ) q = ']';
while( z[iIn] ){
if( z[iIn]==q ){
if( z[iIn+1]!=q ){
/* Character iIn was the close quote. */
iIn++;
break;
/* Set stack variable q to the close-quote character */
if( q=='[' || q=='\'' || q=='"' || q=='`' ){
int iIn = 1;
int iOut = 0;
if( q=='[' ) q = ']';
while( z[iIn] ){
if( z[iIn]==q ){
if( z[iIn+1]!=q ){
/* Character iIn was the close quote. */
iIn++;
break;
}else{
/* Character iIn and iIn+1 form an escaped quote character. Skip
** the input cursor past both and copy a single quote character
** to the output buffer. */
iIn += 2;
z[iOut++] = q;
}
}else{
/* Character iIn and iIn+1 form an escaped quote character. Skip
** the input cursor past both and copy a single quote character
** to the output buffer. */
iIn += 2;
z[iOut++] = q;
z[iOut++] = z[iIn++];
}
}else{
z[iOut++] = z[iIn++];
}
z[iOut] = '\0';
}
z[iOut] = '\0';
}
}
@ -210,6 +212,37 @@ static sqlite3_stmt *unionPrepare(
return pRet;
}
/*
** Like unionPrepare(), except prepare the results of vprintf(zFmt, ...)
** instead of a constant SQL string.
*/
static sqlite3_stmt *unionPreparePrintf(
int *pRc, /* IN/OUT: Error code */
char **pzErr, /* OUT: Error message */
sqlite3 *db, /* Database handle */
const char *zFmt, /* printf() format string */
... /* Trailing printf args */
){
sqlite3_stmt *pRet = 0;
char *zSql;
va_list ap;
va_start(ap, zFmt);
zSql = sqlite3_vmprintf(zFmt, ap);
if( *pRc==SQLITE_OK ){
if( zSql==0 ){
*pRc = SQLITE_NOMEM;
}else{
pRet = unionPrepare(pRc, db, zSql, pzErr);
}
}
sqlite3_free(zSql);
va_end(ap);
return pRet;
}
/*
** Call sqlite3_reset() on SQL statement pStmt. If *pRc is set to
** SQLITE_OK when this function is called, then it is set to the
@ -390,16 +423,10 @@ static int unionConnect(
** the results by the "minimum rowid" field. This makes it easier to
** check that there are no rowid range overlaps between source tables
** and that the UnionTab.aSrc[] array is always sorted by rowid. */
if( zArg ){
unionDequote(zArg);
zSql = sqlite3_mprintf("SELECT * FROM (%s) ORDER BY 3", zArg);
sqlite3_free(zArg);
zArg = 0;
}
if( zSql==0 ){
rc = SQLITE_NOMEM;
}
pStmt = unionPrepare(&rc, db, zSql, pzErr);
unionDequote(zArg);
pStmt = unionPreparePrintf(&rc, pzErr, db,
"SELECT * FROM (%z) ORDER BY 3", zArg
);
/* Allocate the UnionTab structure */
pTab = unionMalloc(&rc, sizeof(UnionTab));
@ -443,9 +470,7 @@ static int unionConnect(
}
unionFinalize(&rc, pStmt);
pStmt = 0;
sqlite3_free(zArg);
sqlite3_free(zSql);
zArg = 0;
zSql = 0;
/* Verify that all source tables exist and have compatible schemas. */
@ -455,18 +480,14 @@ static int unionConnect(
}
/* Compose a CREATE TABLE statement and pass it to declare_vtab() */
if( rc==SQLITE_OK ){
zSql = sqlite3_mprintf("SELECT "
"'CREATE TABLE xyz('"
" || group_concat(quote(name) || ' ' || type, ', ')"
" || ')',"
"max((cid+1) * (type='INTEGER' COLLATE nocase AND pk=1))-1 "
"FROM pragma_table_info(%Q, ?)",
pTab->aSrc[0].zTab, pTab->aSrc[0].zDb
);
if( zSql==0 ) rc = SQLITE_NOMEM;
}
pStmt = unionPrepare(&rc, db, zSql, pzErr);
pStmt = unionPreparePrintf(&rc, pzErr, db, "SELECT "
"'CREATE TABLE xyz('"
" || group_concat(quote(name) || ' ' || type, ', ')"
" || ')',"
"max((cid+1) * (type='INTEGER' COLLATE nocase AND pk=1))-1 "
"FROM pragma_table_info(%Q, ?)",
pTab->aSrc[0].zTab, pTab->aSrc[0].zDb
);
if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
const char *zDecl = (const char*)sqlite3_column_text(pStmt, 0);
rc = sqlite3_declare_vtab(db, zDecl);