relational.md
In duckdb: DBI Package for the DuckDB Database Management System

we can create comparison expressions with appropriate operators

Code
  expr_comparison("=", list(expr_constant(-42), expr_constant(42L)))
Message
  DuckDB Expression: (-42.0 = 42)

Code
  expr_comparison("!=", list(expr_constant(-42), expr_constant(42L)))
Message
  DuckDB Expression: (-42.0 != 42)

Code
  expr_comparison(">", list(expr_constant(-42), expr_constant(42L)))
Message
  DuckDB Expression: (-42.0 > 42)

Code
  expr_comparison("<", list(expr_constant(-42), expr_constant(42L)))
Message
  DuckDB Expression: (-42.0 < 42)

Code
  expr_comparison(">=", list(expr_constant(-42), expr_constant(42L)))
Message
  DuckDB Expression: (-42.0 >= 42)

Code
  expr_comparison("<=", list(expr_constant(-42), expr_constant(42L)))
Message
  DuckDB Expression: (-42.0 <= 42)

we cannot create comparison expressions with inappropriate operators

Code
  expr_comparison("z", list(expr_constant(-42), expr_constant(42L)))
Condition
  Error:
  ! expr_comparison: Invalid comparison operator

Code
  expr_comparison("2", list(expr_constant(-42), expr_constant(42L)))
Condition
  Error:
  ! expr_comparison: Invalid comparison operator

Code
  expr_comparison("-", list(expr_constant(-42), expr_constant(42L)))
Condition
  Error:
  ! expr_comparison: Invalid comparison operator

the altrep-conversion for relations works

Code
  last_rel
Message
  DuckDB Relation: 
  ---------------------
  --- Relation Tree ---
  ---------------------
  r_dataframe_scan(0x...)

  ---------------------
  -- Result Columns  --
  ---------------------
  - Sepal.Length (DOUBLE)
  - Sepal.Width (DOUBLE)
  - Petal.Length (DOUBLE)
  - Petal.Width (DOUBLE)
  - Species (VARCHAR)

rel_tostring()

Code
  writeLines(rel_tostring(proj))
Output
  ---------------------
  --- Relation Tree ---
  ---------------------
  Projection [x as x]
    r_dataframe_scan(0x...)

  ---------------------
  -- Result Columns  --
  ---------------------
  - x (DOUBLE)

Code
  writeLines(rel_tostring(proj, "tree"))
Output
  Projection [x as x]
    r_dataframe_scan(0x...)

rel_explain()

Code
  writeLines(rel_explain_df(proj)[[2]])
Output
  ┌───────────────────────────┐
  │     R_DATAFRAME_SCAN      │
  │    ────────────────────   │
  │      Text: data.frame     │
  │       Projections: x      │
  │                           │
  │           ~1 row          │
  └───────────────────────────┘

Code
  writeLines(rel_explain_df(proj, "analyze")[[2]])
Output
  Query profiling is disabled. Use 'PRAGMA enable_profiling;' to enable profiling!

Code
  writeLines(rel_explain_df(proj, "standard", "json")[[2]])
Output
  [
      {
          "name": "R_DATAFRAME_SCAN ",
          "children": [],
          "extra_info": {
              "Text": "data.frame",
              "Projections": "x",
              "Estimated Cardinality": "1"
          }
      }
  ]

Code
  writeLines(rel_explain_df(proj, "analyze", "json")[[2]])
Output
  {
      "result": "disabled"
  }

Code
  writeLines(rel_explain_df(proj, "standard", "html")[[2]])
Output

  <!DOCTYPE html>
  <html lang="en">
  <head>
      <meta charset="UTF-8">
      <meta name="viewport" content="width=device-width, initial-scale=1.0">
      <link rel="stylesheet" href="https://unpkg.com/treeflex/dist/css/treeflex.css">
      <title>DuckDB Query Plan</title>

      <style>
          body {
              font-family: Arial, sans-serif;
          }

          .tf-tree .tf-nc {
              padding: 0px;
              border: 1px solid #E5E5E5;
          }

          .tf-nc {
              border-radius: 0.5rem;
              padding: 0px;
              min-width: 150px;
              width: auto;
              background-color: #FAFAFA;
              text-align: center;
              position: relative;
          }

          .collapse_button {
              position:relative;
              color: black;
              z-index: 2;
              width: 2em;
              background-color: white;
              height: 2em;
              border-radius: 50%;
              top: 2.25em;
          }

          .collapse_button:hover {
              background-color: #f0f0f0; /* Light gray */
          }

          .collapse_button:active {
              background-color: #e0e0e0; /* Slightly darker gray */
          }

          .hidden {
              display: none !important;
          }

          .title {
              font-weight: bold;
              padding-bottom: 5px;
              color: #fff100;
              box-sizing: border-box;
              background-color: black;
              border-top-left-radius: 0.5rem;
              border-top-right-radius: 0.5rem;
              padding: 10px;
          }

          .content {
              border-top: 1px solid #000;
              text-align: center;
              border-bottom-left-radius: 0.5rem;
              border-bottom-right-radius: 0.5rem;
              padding: 10px;
          }

          .sub-title {
              color: black;
              font-weight: bold;
              padding-top: 5px;
          }

          .sub-title:not(:first-child) {
              border-top: 1px solid #ADADAD;
          }

          .value {
              margin-left: 10px;
              margin-top: 5px;
              color: #3B3B3B;
              margin-bottom: 5px;
          }

          .tf-tree {
              width: 100%;
              height: 100%;
              overflow: visible;
          }
      </style>

  </head>

  <body>
      <div class="tf-tree">
          <ul><li>
          <div class="tf-nc">
              <div class="title">R_DATAFRAME_SCAN </div>
              <div class="content">
                  <div class="sub-title">Text</div>
                  <div class="value">data.frame</div>
                  <div class="sub-title">Projections</div>
                  <div class="value">x</div>
                  <div class="sub-title">Estimated Cardinality</div>
                  <div class="value">1</div>
              </div>

          </div>
      </li></ul>
      </div>

  <script>
  function toggleDisplay(button) {
      const parentLi = button.closest('li');
      const nestedUl = parentLi.querySelector('ul');
      if (nestedUl) {
          const currentDisplay = getComputedStyle(nestedUl).getPropertyValue('display');
          if (currentDisplay === 'none') {
              nestedUl.classList.toggle('hidden');
              button.textContent = '-';
          } else {
              nestedUl.classList.toggle('hidden');
              button.textContent = '+';
          }
      }
  }
  </script>

  </body>
  </html>

Code
  writeLines(rel_explain_df(proj, "standard", "graphviz")[[2]])
Output

  digraph G {
      node [shape=box, style=rounded, fontname="Courier New", fontsize=10];
      node_0_0 [label="R_DATAFRAME_SCAN \n───\nText:\ndata.frame\n───\nProjections:\nx\n───\nEstimated Cardinality:\n1"];

  }

Handle zero-length lists (#186)

Code
  expr_constant(list(integer()))
Message
  DuckDB Expression: []

prudence

Code
  nrow(forbid)
Condition
  Error:
  ! Materialization is disabled, use `collect()` or `as_tibble()` to materialize.
  ℹ Context: GetQueryResult

Code
  nrow(forbid)
Condition
  Error:
  ! Materialization is disabled, use `collect()` or `as_tibble()` to materialize.
  ℹ Context: GetQueryResult

Code
  nrow(four_rows)
Condition
  Error:
  ! Materialization would result in more than 4 rows. Use `collect()` or `as_tibble()` to materialize.
  ℹ Context: GetQueryResult

Code
  nrow(nine_cells)
Condition
  Error:
  ! Materialization would result in more than 4 rows. Use `collect()` or `as_tibble()` to materialize.
  ℹ Context: GetQueryResult

Code
  nrow(bad_rows)
Condition
  Error:
  ! Materialization would result in more than 4 rows. Use `collect()` or `as_tibble()` to materialize.
  ℹ Context: GetQueryResult

Code
  nrow(bad_cells)
Condition
  Error:
  ! Materialization would result in more than 4 rows. Use `collect()` or `as_tibble()` to materialize.
  ℹ Context: GetQueryResult