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Overview
Comment: | Clarification and simplification and result column naming logic. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA3-256: |
68824a439b76a4cca05609a02de7abdc |
User & Date: | drh 2017-07-12 14:10:19.869 |
Context
2017-07-12
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17:08 | The EP_Resolved flag on the Expr object is not required for correctness nor performance, so remove it. (check-in: 54f55d3b79 user: drh tags: trunk) | |
14:10 | Clarification and simplification and result column naming logic. (check-in: 68824a439b user: drh tags: trunk) | |
14:03 | Fix a problem in an lsmtest test case caused by writing data in "text" mode instead of "binary". (check-in: 3e56a79ad8 user: dan tags: trunk) | |
Changes
Changes to src/select.c.
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1564 1565 1566 1567 1568 1569 1570 | if( pList->a[j].iCursor==iCursor ) return pList->a[j].pTab; } return 0; } /* | | > > > > > > > > > > > | > > > > | > > > > > > > > > > | | > | | < | | > > > | < < < | | 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 | if( pList->a[j].iCursor==iCursor ) return pList->a[j].pTab; } return 0; } /* ** Compute the column names for a SELECT statement. ** ** The only guarantee that SQLite makes about column names is that if the ** column has an AS clause assigning it a name, that will be the name used. ** That is the only documented guarantee. However, countless applications ** developed over the years have made baseless assumptions about column names ** and will break if those assumptions changes. Hence, use extreme caution ** when modifying this routine to avoid breaking legacy. ** ** See Also: sqlite3ColumnsFromExprList() ** ** The PRAGMA short_column_names and PRAGMA full_column_names settings are ** deprecated. The default setting is short=ON, full=OFF. 99.9% of all ** applications should operate this way. Nevertheless, we need to support the ** other modes for legacy: ** ** short=OFF, full=OFF: Column name is the text of the expression has it ** originally appears in the SELECT statement. In ** other words, the zSpan of the result expression. ** ** short=ON, full=OFF: (This is the default setting). If the result ** refers directly to a table column, then the result ** column name is just the table column name: COLUMN. ** Otherwise use zSpan. ** ** full=ON, short=ANY: If the result refers directly to a table column, ** then the result column name with the table name ** prefix, ex: TABLE.COLUMN. Otherwise use zSpan. */ static void generateColumnNames( Parse *pParse, /* Parser context */ SrcList *pTabList, /* The FROM clause of the SELECT */ ExprList *pEList /* Expressions defining the result set */ ){ Vdbe *v = pParse->pVdbe; int i; Table *pTab; sqlite3 *db = pParse->db; int fullName; /* TABLE.COLUMN if no AS clause and is a direct table ref */ int srcName; /* COLUMN or TABLE.COLUMN if no AS clause and is direct */ #ifndef SQLITE_OMIT_EXPLAIN /* If this is an EXPLAIN, skip this step */ if( pParse->explain ){ return; } #endif if( pParse->colNamesSet || db->mallocFailed ) return; assert( v!=0 ); assert( pTabList!=0 ); pParse->colNamesSet = 1; fullName = (db->flags & SQLITE_FullColNames)!=0; srcName = (db->flags & SQLITE_ShortColNames)!=0 || fullName; sqlite3VdbeSetNumCols(v, pEList->nExpr); for(i=0; i<pEList->nExpr; i++){ Expr *p = pEList->a[i].pExpr; assert( p!=0 ); if( pEList->a[i].zName ){ /* An AS clause always takes first priority */ char *zName = pEList->a[i].zName; sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT); }else if( srcName && (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN) && (pTab = tableWithCursor(pTabList, p->iTable))!=0 ){ char *zCol; int iCol = p->iColumn; if( iCol<0 ) iCol = pTab->iPKey; assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) ); if( iCol<0 ){ zCol = "rowid"; }else{ zCol = pTab->aCol[iCol].zName; } if( fullName ){ char *zName = 0; zName = sqlite3MPrintf(db, "%s.%s", pTab->zName, zCol); sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_DYNAMIC); }else{ sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, SQLITE_TRANSIENT); } }else{ |
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1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 | ** All column names will be unique. ** ** Only the column names are computed. Column.zType, Column.zColl, ** and other fields of Column are zeroed. ** ** Return SQLITE_OK on success. If a memory allocation error occurs, ** store NULL in *paCol and 0 in *pnCol and return SQLITE_NOMEM. */ int sqlite3ColumnsFromExprList( Parse *pParse, /* Parsing context */ ExprList *pEList, /* Expr list from which to derive column names */ i16 *pnCol, /* Write the number of columns here */ Column **paCol /* Write the new column list here */ ){ sqlite3 *db = pParse->db; /* Database connection */ int i, j; /* Loop counters */ u32 cnt; /* Index added to make the name unique */ Column *aCol, *pCol; /* For looping over result columns */ int nCol; /* Number of columns in the result set */ | > > > > > > > > > < < | < | | 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 | ** All column names will be unique. ** ** Only the column names are computed. Column.zType, Column.zColl, ** and other fields of Column are zeroed. ** ** Return SQLITE_OK on success. If a memory allocation error occurs, ** store NULL in *paCol and 0 in *pnCol and return SQLITE_NOMEM. ** ** The only guarantee that SQLite makes about column names is that if the ** column has an AS clause assigning it a name, that will be the name used. ** That is the only documented guarantee. However, countless applications ** developed over the years have made baseless assumptions about column names ** and will break if those assumptions changes. Hence, use extreme caution ** when modifying this routine to avoid breaking legacy. ** ** See Also: generateColumnNames() */ int sqlite3ColumnsFromExprList( Parse *pParse, /* Parsing context */ ExprList *pEList, /* Expr list from which to derive column names */ i16 *pnCol, /* Write the number of columns here */ Column **paCol /* Write the new column list here */ ){ sqlite3 *db = pParse->db; /* Database connection */ int i, j; /* Loop counters */ u32 cnt; /* Index added to make the name unique */ Column *aCol, *pCol; /* For looping over result columns */ int nCol; /* Number of columns in the result set */ char *zName; /* Column name */ int nName; /* Size of name in zName[] */ Hash ht; /* Hash table of column names */ sqlite3HashInit(&ht); if( pEList ){ nCol = pEList->nExpr; aCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol); testcase( aCol==0 ); }else{ nCol = 0; aCol = 0; } assert( nCol==(i16)nCol ); *pnCol = nCol; *paCol = aCol; for(i=0, pCol=aCol; i<nCol && !db->mallocFailed; i++, pCol++){ /* Get an appropriate name for the column */ if( (zName = pEList->a[i].zName)!=0 ){ /* If the column contains an "AS <name>" phrase, use <name> as the name */ }else{ Expr *pColExpr = sqlite3ExprSkipCollate(pEList->a[i].pExpr); while( pColExpr->op==TK_DOT ){ pColExpr = pColExpr->pRight; assert( pColExpr!=0 ); } if( pColExpr->op==TK_COLUMN && pColExpr->pTab!=0 ){ /* For columns use the column name name */ int iCol = pColExpr->iColumn; Table *pTab = pColExpr->pTab; if( iCol<0 ) iCol = pTab->iPKey; zName = iCol>=0 ? pTab->aCol[iCol].zName : "rowid"; }else if( pColExpr->op==TK_ID ){ assert( !ExprHasProperty(pColExpr, EP_IntValue) ); zName = pColExpr->u.zToken; }else{ /* Use the original text of the column expression as its name */ |
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