> ## Documentation Index > Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Proyecciones > Página que describe qué son las proyecciones, cómo pueden usarse para mejorar el rendimiento de las consultas y en qué se diferencian de las vistas materializadas. export const RunnableCode = ({children, run = false, showStats = true}) => { const [results, setResults] = useState(null); const [error, setError] = useState(null); const [loading, setLoading] = useState(false); const [showResults, setShowResults] = useState(false); const [stats, setStats] = useState(null); const [isDark, setIsDark] = useState(false); const [hoveredRow, setHoveredRow] = useState(-1); const codeRef = useRef(null); useEffect(() => { if (typeof window !== "undefined") { const check = () => setIsDark(document.documentElement.classList.contains("dark")); check(); const observer = new MutationObserver(check); observer.observe(document.documentElement, { attributes: true, attributeFilter: ["class"] }); return () => observer.disconnect(); } }, []); useEffect(() => { if (codeRef.current) { const block = codeRef.current.querySelector(".code-block"); if (block) { block.style.marginBottom = "0"; block.style.marginTop = "0"; block.style.borderBottomLeftRadius = "0"; block.style.borderBottomRightRadius = "0"; } } }); const getSqlText = () => { if (!codeRef.current) return ""; const code = codeRef.current.querySelector("code"); return (code || codeRef.current).textContent.trim(); }; const executeQuery = async () => { const sql = getSqlText(); if (!sql) return; setLoading(true); setError(null); setResults(null); setShowResults(true); try { const cleanQuery = sql.replace(/;$/, "").trim(); const params = new URLSearchParams({ query: cleanQuery, default_format: "JSONCompact", result_overflow_mode: "break", read_overflow_mode: "break", allow_experimental_analyzer: "1" }); const res = await fetch(`https://sql-clickhouse.clickhouse.com/?${params.toString()}`, { method: "POST", headers: { Authorization: `Basic ${btoa(`demo:`)}` } }); const text = await res.text(); if (!res.ok) { setError(text || `HTTP ${res.status}`); setLoading(false); return; } const json = JSON.parse(text); setResults(json); setStats(json.statistics || null); } catch (err) { setError(err.message || "Error al ejecutar la consulta"); } setLoading(false); }; useEffect(() => { if (run) executeQuery(); }, []); const formatRows = n => { if (n >= 1e9) return `${(n / 1e9).toFixed(1)}B`; if (n >= 1e6) return `${(n / 1e6).toFixed(1)}M`; if (n >= 1e3) return `${(n / 1e3).toFixed(1)}K`; return String(n); }; const formatBytes = b => { if (b >= 1e9) return `${(b / 1e9).toFixed(2)} GB`; if (b >= 1e6) return `${(b / 1e6).toFixed(2)} MB`; if (b >= 1e3) return `${(b / 1e3).toFixed(2)} KB`; return `${b} B`; }; const isNumericType = type => { return (/^(UInt|Int|Float|Decimal)/).test(type); }; const isHyperlink = value => { return typeof value === "string" && (/^https?:\/\//).test(value); }; const computeColumnExtremes = (meta, data) => { const extremes = {}; for (let i = 0; i < meta.length; i++) { if (isNumericType(meta[i].type)) { let min = Infinity, max = -Infinity; for (const row of data) { const v = Number(row[i]); if (!isNaN(v)) { if (v < min) min = v; if (v > max) max = v; } } if (max > -Infinity) { extremes[i] = { min, max }; } } } return extremes; }; const computeColumnWidths = (meta, data) => { const lengths = meta.map((col, i) => { const headerLen = col.name.length + col.type.length + 1; let maxData = 0; for (const row of data) { const v = row[i]; const len = v === null ? 4 : String(v).length; if (len > maxData) maxData = len; } return Math.max(headerLen, maxData); }); const total = lengths.reduce((s, l) => s + l, 0); return lengths.map(l => `${(l / total * 100).toFixed(1)}%`); }; const copyResultsAsTSV = () => { if (!results || !results.meta || !results.data) return; const header = results.meta.map(col => col.name).join("\t"); const rows = results.data.map(row => row.map(cell => cell === null ? "NULL" : String(cell)).join("\t")); const tsv = [header, ...rows].join("\n"); navigator.clipboard.writeText(tsv); }; const borderColor = isDark ? "rgba(255,255,255,0.15)" : "#e5e7eb"; const bgColor = isDark ? "rgba(255,255,255,0.05)" : "#f9fafb"; const headerBg = isDark ? "#2a2a2a" : "#f3f4f6"; const textColor = isDark ? "#e5e7eb" : "#1f2937"; const mutedColor = isDark ? "#d1d5db" : "#6b7280"; const accentColor = isDark ? "#FAFF69" : "#323232"; const accentTextColor = isDark ? "#000" : "#fff"; const barColor = isDark ? "#35372f" : "#d2d2d2"; const cellBg = isDark ? "#1f201b" : "#ffffff"; const cellBgHover = isDark ? "lch(15.8 0 0)" : "#f0f0f0"; const extremes = results && results.meta && results.data ? computeColumnExtremes(results.meta, results.data) : {}; const colWidths = results && results.meta && results.data ? computeColumnWidths(results.meta, results.data) : []; const getCellBarStyle = (cell, ci, ri) => { if (cell === null) return null; const colMeta = results.meta[ci]; if (!isNumericType(colMeta.type) || !extremes[ci] || results.data.length <= 1 || extremes[ci].max <= 0) return null; const ratio = 100 * Number(cell) / extremes[ci].max; const bg = ri === hoveredRow ? cellBgHover : cellBg; return { background: `linear-gradient(to right, ${barColor} 0%, ${barColor} ${ratio}%, ${bg} ${ratio}%, ${bg} 100%)` }; }; const renderCell = (cell, ci) => { if (cell === null) { return NULL; } const value = String(cell); if (isHyperlink(value)) { return {value} ; } return value; }; return
{}
{children}
{}
{results && } {showStats && stats && Leídas {formatRows(stats.rows_read)} filas, {formatBytes(stats.bytes_read)} en {stats.elapsed.toFixed(3)}s }
{} {showResults &&
{loading &&
Ejecutando consulta...
} {error &&
{error}
} {results && results.meta && results.data &&
{results.meta.map((col, i) =>
1 ? "right" : "left", backgroundColor: headerBg, borderBottom: `1px solid ${borderColor}`, color: textColor, fontWeight: 600, fontSize: "12px", whiteSpace: "nowrap", overflow: "hidden", textOverflow: "ellipsis" }}> {col.name} {col.type}
)} {results.data.map((row, ri) => row.map((cell, ci) =>
setHoveredRow(ri)} onMouseLeave={() => setHoveredRow(-1)} style={{ padding: "4px 12px", color: textColor, whiteSpace: "nowrap", overflow: "hidden", textOverflow: "ellipsis", textAlign: isNumericType(results.meta[ci].type) && results.meta.length > 1 ? "right" : "left", borderBottom: `1px solid ${borderColor}`, backgroundColor: ri === hoveredRow ? cellBgHover : ri % 2 === 0 ? "transparent" : bgColor, transition: "background-color 0.1s", ...getCellBarStyle(cell, ci, ri) }}> {renderCell(cell, ci)}
))}
} {results && results.data &&
{results.rows} fila{results.rows !== 1 ? "s" : ""}
}
}
; }; export const Image = ({img, alt, size = "lg", background}) => { const normalizedSize = ["sm", "md", "lg"].includes(size) ? size : "lg"; const backgroundColor = background === "white" ? "white" : background === "black" ? "rgb(31 31 28)" : undefined; return
{alt}
; };
## Introducción
ClickHouse ofrece varios mecanismos para acelerar las consultas analíticas sobre grandes volúmenes de datos en escenarios en tiempo real. Uno de esos mecanismos para acelerar las consultas es el uso de *proyecciones*. Las proyecciones ayudan a optimizar las consultas creando una reordenación de los datos según los atributos de interés. Esto puede ser: 1. Una reordenación completa 2. Un subconjunto de la tabla original con un orden diferente 3. Una agregación precalculada (similar a una vista materializada), pero con un orden alineado con la agregación.